RISC-V: KVM: Add in-kernel virtualization of AIA IMSIC

We can have AIA IMSIC support for both HS-level and VS-level but
the VS-level IMSICs are optional. We use the VS-level IMSICs for
Guest/VM whenever available otherwise we fallback to software
emulation of AIA IMSIC.

This patch adds in-kernel virtualization of AIA IMSIC.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

2 files changed, 915 insertions, 0 deletions

diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 94c43702c765..c1d1356387ff 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -29,3 +29,4 @@ kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o vcpu_sbi_pmu.o
 kvm-y += aia.o
 kvm-y += aia_device.o
 kvm-y += aia_aplic.o
+kvm-y += aia_imsic.o
diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c
new file mode 100644
index 000000000000..0e6ecf067757
--- /dev/null
+++ b/arch/riscv/kvm/aia_imsic.c
@@ -0,0 +1,914 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Western Digital Corporation or its affiliates.
+ * Copyright (C) 2022 Ventana Micro Systems Inc.
+ *
+ * Authors:
+ *	Anup Patel <apatel@ventanamicro.com>
+ */
+
+#include <linux/atomic.h>
+#include <linux/bitmap.h>
+#include <linux/kvm_host.h>
+#include <linux/math.h>
+#include <linux/spinlock.h>
+#include <linux/swab.h>
+#include <kvm/iodev.h>
+#include <asm/csr.h>
+#include <asm/kvm_aia_imsic.h>
+
+#define IMSIC_MAX_EIX	(IMSIC_MAX_ID / BITS_PER_TYPE(u64))
+
+struct imsic_mrif_eix {
+	unsigned long eip[BITS_PER_TYPE(u64) / BITS_PER_LONG];
+	unsigned long eie[BITS_PER_TYPE(u64) / BITS_PER_LONG];
+};
+
+struct imsic_mrif {
+	struct imsic_mrif_eix eix[IMSIC_MAX_EIX];
+	unsigned long eithreshold;
+	unsigned long eidelivery;
+};
+
+struct imsic {
+	struct kvm_io_device iodev;
+
+	u32 nr_msis;
+	u32 nr_eix;
+	u32 nr_hw_eix;
+
+	/*
+	 * At any point in time, the register state is in
+	 * one of the following places:
+	 *
+	 * 1) Hardware: IMSIC VS-file (vsfile_cpu >= 0)
+	 * 2) Software: IMSIC SW-file (vsfile_cpu < 0)
+	 */
+
+	/* IMSIC VS-file */
+	rwlock_t vsfile_lock;
+	int vsfile_cpu;
+	int vsfile_hgei;
+	void __iomem *vsfile_va;
+	phys_addr_t vsfile_pa;
+
+	/* IMSIC SW-file */
+	struct imsic_mrif *swfile;
+	phys_addr_t swfile_pa;
+};
+
+#define imsic_vs_csr_read(__c)			\
+({						\
+	unsigned long __r;			\
+	csr_write(CSR_VSISELECT, __c);		\
+	__r = csr_read(CSR_VSIREG);		\
+	__r;					\
+})
+
+#define imsic_read_switchcase(__ireg)			\
+	case __ireg:					\
+		return imsic_vs_csr_read(__ireg);
+#define imsic_read_switchcase_2(__ireg)			\
+	imsic_read_switchcase(__ireg + 0)		\
+	imsic_read_switchcase(__ireg + 1)
+#define imsic_read_switchcase_4(__ireg)			\
+	imsic_read_switchcase_2(__ireg + 0)		\
+	imsic_read_switchcase_2(__ireg + 2)
+#define imsic_read_switchcase_8(__ireg)			\
+	imsic_read_switchcase_4(__ireg + 0)		\
+	imsic_read_switchcase_4(__ireg + 4)
+#define imsic_read_switchcase_16(__ireg)		\
+	imsic_read_switchcase_8(__ireg + 0)		\
+	imsic_read_switchcase_8(__ireg + 8)
+#define imsic_read_switchcase_32(__ireg)		\
+	imsic_read_switchcase_16(__ireg + 0)		\
+	imsic_read_switchcase_16(__ireg + 16)
+#define imsic_read_switchcase_64(__ireg)		\
+	imsic_read_switchcase_32(__ireg + 0)		\
+	imsic_read_switchcase_32(__ireg + 32)
+
+static unsigned long imsic_eix_read(int ireg)
+{
+	switch (ireg) {
+	imsic_read_switchcase_64(IMSIC_EIP0)
+	imsic_read_switchcase_64(IMSIC_EIE0)
+	};
+
+	return 0;
+}
+
+#define imsic_vs_csr_swap(__c, __v)		\
+({						\
+	unsigned long __r;			\
+	csr_write(CSR_VSISELECT, __c);		\
+	__r = csr_swap(CSR_VSIREG, __v);	\
+	__r;					\
+})
+
+#define imsic_swap_switchcase(__ireg, __v)		\
+	case __ireg:					\
+		return imsic_vs_csr_swap(__ireg, __v);
+#define imsic_swap_switchcase_2(__ireg, __v)		\
+	imsic_swap_switchcase(__ireg + 0, __v)		\
+	imsic_swap_switchcase(__ireg + 1, __v)
+#define imsic_swap_switchcase_4(__ireg, __v)		\
+	imsic_swap_switchcase_2(__ireg + 0, __v)	\
+	imsic_swap_switchcase_2(__ireg + 2, __v)
+#define imsic_swap_switchcase_8(__ireg, __v)		\
+	imsic_swap_switchcase_4(__ireg + 0, __v)	\
+	imsic_swap_switchcase_4(__ireg + 4, __v)
+#define imsic_swap_switchcase_16(__ireg, __v)		\
+	imsic_swap_switchcase_8(__ireg + 0, __v)	\
+	imsic_swap_switchcase_8(__ireg + 8, __v)
+#define imsic_swap_switchcase_32(__ireg, __v)		\
+	imsic_swap_switchcase_16(__ireg + 0, __v)	\
+	imsic_swap_switchcase_16(__ireg + 16, __v)
+#define imsic_swap_switchcase_64(__ireg, __v)		\
+	imsic_swap_switchcase_32(__ireg + 0, __v)	\
+	imsic_swap_switchcase_32(__ireg + 32, __v)
+
+static unsigned long imsic_eix_swap(int ireg, unsigned long val)
+{
+	switch (ireg) {
+	imsic_swap_switchcase_64(IMSIC_EIP0, val)
+	imsic_swap_switchcase_64(IMSIC_EIE0, val)
+	};
+
+	return 0;
+}
+
+#define imsic_vs_csr_write(__c, __v)		\
+do {						\
+	csr_write(CSR_VSISELECT, __c);		\
+	csr_write(CSR_VSIREG, __v);		\
+} while (0)
+
+#define imsic_write_switchcase(__ireg, __v)		\
+	case __ireg:					\
+		imsic_vs_csr_write(__ireg, __v);	\
+		break;
+#define imsic_write_switchcase_2(__ireg, __v)		\
+	imsic_write_switchcase(__ireg + 0, __v)		\
+	imsic_write_switchcase(__ireg + 1, __v)
+#define imsic_write_switchcase_4(__ireg, __v)		\
+	imsic_write_switchcase_2(__ireg + 0, __v)	\
+	imsic_write_switchcase_2(__ireg + 2, __v)
+#define imsic_write_switchcase_8(__ireg, __v)		\
+	imsic_write_switchcase_4(__ireg + 0, __v)	\
+	imsic_write_switchcase_4(__ireg + 4, __v)
+#define imsic_write_switchcase_16(__ireg, __v)		\
+	imsic_write_switchcase_8(__ireg + 0, __v)	\
+	imsic_write_switchcase_8(__ireg + 8, __v)
+#define imsic_write_switchcase_32(__ireg, __v)		\
+	imsic_write_switchcase_16(__ireg + 0, __v)	\
+	imsic_write_switchcase_16(__ireg + 16, __v)
+#define imsic_write_switchcase_64(__ireg, __v)		\
+	imsic_write_switchcase_32(__ireg + 0, __v)	\
+	imsic_write_switchcase_32(__ireg + 32, __v)
+
+static void imsic_eix_write(int ireg, unsigned long val)
+{
+	switch (ireg) {
+	imsic_write_switchcase_64(IMSIC_EIP0, val)
+	imsic_write_switchcase_64(IMSIC_EIE0, val)
+	};
+}
+
+#define imsic_vs_csr_set(__c, __v)		\
+do {						\
+	csr_write(CSR_VSISELECT, __c);		\
+	csr_set(CSR_VSIREG, __v);		\
+} while (0)
+
+#define imsic_set_switchcase(__ireg, __v)		\
+	case __ireg:					\
+		imsic_vs_csr_set(__ireg, __v);		\
+		break;
+#define imsic_set_switchcase_2(__ireg, __v)		\
+	imsic_set_switchcase(__ireg + 0, __v)		\
+	imsic_set_switchcase(__ireg + 1, __v)
+#define imsic_set_switchcase_4(__ireg, __v)		\
+	imsic_set_switchcase_2(__ireg + 0, __v)		\
+	imsic_set_switchcase_2(__ireg + 2, __v)
+#define imsic_set_switchcase_8(__ireg, __v)		\
+	imsic_set_switchcase_4(__ireg + 0, __v)		\
+	imsic_set_switchcase_4(__ireg + 4, __v)
+#define imsic_set_switchcase_16(__ireg, __v)		\
+	imsic_set_switchcase_8(__ireg + 0, __v)		\
+	imsic_set_switchcase_8(__ireg + 8, __v)
+#define imsic_set_switchcase_32(__ireg, __v)		\
+	imsic_set_switchcase_16(__ireg + 0, __v)	\
+	imsic_set_switchcase_16(__ireg + 16, __v)
+#define imsic_set_switchcase_64(__ireg, __v)		\
+	imsic_set_switchcase_32(__ireg + 0, __v)	\
+	imsic_set_switchcase_32(__ireg + 32, __v)
+
+static void imsic_eix_set(int ireg, unsigned long val)
+{
+	switch (ireg) {
+	imsic_set_switchcase_64(IMSIC_EIP0, val)
+	imsic_set_switchcase_64(IMSIC_EIE0, val)
+	};
+}
+
+static unsigned long imsic_mrif_atomic_rmw(struct imsic_mrif *mrif,
+					   unsigned long *ptr,
+					   unsigned long new_val,
+					   unsigned long wr_mask)
+{
+	unsigned long old_val = 0, tmp = 0;
+
+	__asm__ __volatile__ (
+		"0:	lr.w.aq   %1, %0\n"
+		"	and       %2, %1, %3\n"
+		"	or        %2, %2, %4\n"
+		"	sc.w.rl   %2, %2, %0\n"
+		"	bnez      %2, 0b"
+		: "+A" (*ptr), "+r" (old_val), "+r" (tmp)
+		: "r" (~wr_mask), "r" (new_val & wr_mask)
+		: "memory");
+
+	return old_val;
+}
+
+static unsigned long imsic_mrif_atomic_or(struct imsic_mrif *mrif,
+					  unsigned long *ptr,
+					  unsigned long val)
+{
+	return atomic_long_fetch_or(val, (atomic_long_t *)ptr);
+}
+
+#define imsic_mrif_atomic_write(__mrif, __ptr, __new_val)	\
+		imsic_mrif_atomic_rmw(__mrif, __ptr, __new_val, -1UL)
+#define imsic_mrif_atomic_read(__mrif, __ptr)			\
+		imsic_mrif_atomic_or(__mrif, __ptr, 0)
+
+static u32 imsic_mrif_topei(struct imsic_mrif *mrif, u32 nr_eix, u32 nr_msis)
+{
+	struct imsic_mrif_eix *eix;
+	u32 i, imin, imax, ei, max_msi;
+	unsigned long eipend[BITS_PER_TYPE(u64) / BITS_PER_LONG];
+	unsigned long eithreshold = imsic_mrif_atomic_read(mrif,
+							&mrif->eithreshold);
+
+	max_msi = (eithreshold && (eithreshold <= nr_msis)) ?
+		   eithreshold : nr_msis;
+	for (ei = 0; ei < nr_eix; ei++) {
+		eix = &mrif->eix[ei];
+		eipend[0] = imsic_mrif_atomic_read(mrif, &eix->eie[0]) &
+			    imsic_mrif_atomic_read(mrif, &eix->eip[0]);
+#ifdef CONFIG_32BIT
+		eipend[1] = imsic_mrif_atomic_read(mrif, &eix->eie[1]) &
+			    imsic_mrif_atomic_read(mrif, &eix->eip[1]);
+		if (!eipend[0] && !eipend[1])
+#else
+		if (!eipend[0])
+#endif
+			continue;
+
+		imin = ei * BITS_PER_TYPE(u64);
+		imax = ((imin + BITS_PER_TYPE(u64)) < max_msi) ?
+			imin + BITS_PER_TYPE(u64) : max_msi;
+		for (i = (!imin) ? 1 : imin; i < imax; i++) {
+			if (test_bit(i - imin, eipend))
+				return (i << TOPEI_ID_SHIFT) | i;
+		}
+	}
+
+	return 0;
+}
+
+static int imsic_mrif_rmw(struct imsic_mrif *mrif, u32 nr_eix,
+			  unsigned long isel, unsigned long *val,
+			  unsigned long new_val, unsigned long wr_mask)
+{
+	bool pend;
+	struct imsic_mrif_eix *eix;
+	unsigned long *ei, num, old_val = 0;
+
+	switch (isel) {
+	case IMSIC_EIDELIVERY:
+		old_val = imsic_mrif_atomic_rmw(mrif, &mrif->eidelivery,
+						new_val, wr_mask & 0x1);
+		break;
+	case IMSIC_EITHRESHOLD:
+		old_val = imsic_mrif_atomic_rmw(mrif, &mrif->eithreshold,
+				new_val, wr_mask & (IMSIC_MAX_ID - 1));
+		break;
+	case IMSIC_EIP0 ... IMSIC_EIP63:
+	case IMSIC_EIE0 ... IMSIC_EIE63:
+		if (isel >= IMSIC_EIP0 && isel <= IMSIC_EIP63) {
+			pend = true;
+			num = isel - IMSIC_EIP0;
+		} else {
+			pend = false;
+			num = isel - IMSIC_EIE0;
+		}
+
+		if ((num / 2) >= nr_eix)
+			return -EINVAL;
+		eix = &mrif->eix[num / 2];
+
+#ifndef CONFIG_32BIT
+		if (num & 0x1)
+			return -EINVAL;
+		ei = (pend) ? &eix->eip[0] : &eix->eie[0];
+#else
+		ei = (pend) ? &eix->eip[num & 0x1] : &eix->eie[num & 0x1];
+#endif
+
+		/* Bit0 of EIP0 or EIE0 is read-only */
+		if (!num)
+			wr_mask &= ~BIT(0);
+
+		old_val = imsic_mrif_atomic_rmw(mrif, ei, new_val, wr_mask);
+		break;
+	default:
+		return -ENOENT;
+	};
+
+	if (val)
+		*val = old_val;
+
+	return 0;
+}
+
+struct imsic_vsfile_read_data {
+	int hgei;
+	u32 nr_eix;
+	bool clear;
+	struct imsic_mrif *mrif;
+};
+
+static void imsic_vsfile_local_read(void *data)
+{
+	u32 i;
+	struct imsic_mrif_eix *eix;
+	struct imsic_vsfile_read_data *idata = data;
+	struct imsic_mrif *mrif = idata->mrif;
+	unsigned long new_hstatus, old_hstatus, old_vsiselect;
+
+	old_vsiselect = csr_read(CSR_VSISELECT);
+	old_hstatus = csr_read(CSR_HSTATUS);
+	new_hstatus = old_hstatus & ~HSTATUS_VGEIN;
+	new_hstatus |= ((unsigned long)idata->hgei) << HSTATUS_VGEIN_SHIFT;
+	csr_write(CSR_HSTATUS, new_hstatus);
+
+	/*
+	 * We don't use imsic_mrif_atomic_xyz() functions to store
+	 * values in MRIF because imsic_vsfile_read() is always called
+	 * with pointer to temporary MRIF on stack.
+	 */
+
+	if (idata->clear) {
+		mrif->eidelivery = imsic_vs_csr_swap(IMSIC_EIDELIVERY, 0);
+		mrif->eithreshold = imsic_vs_csr_swap(IMSIC_EITHRESHOLD, 0);
+		for (i = 0; i < idata->nr_eix; i++) {
+			eix = &mrif->eix[i];
+			eix->eip[0] = imsic_eix_swap(IMSIC_EIP0 + i * 2, 0);
+			eix->eie[0] = imsic_eix_swap(IMSIC_EIE0 + i * 2, 0);
+#ifdef CONFIG_32BIT
+			eix->eip[1] = imsic_eix_swap(IMSIC_EIP0 + i * 2 + 1, 0);
+			eix->eie[1] = imsic_eix_swap(IMSIC_EIE0 + i * 2 + 1, 0);
+#endif
+		}
+	} else {
+		mrif->eidelivery = imsic_vs_csr_read(IMSIC_EIDELIVERY);
+		mrif->eithreshold = imsic_vs_csr_read(IMSIC_EITHRESHOLD);
+		for (i = 0; i < idata->nr_eix; i++) {
+			eix = &mrif->eix[i];
+			eix->eip[0] = imsic_eix_read(IMSIC_EIP0 + i * 2);
+			eix->eie[0] = imsic_eix_read(IMSIC_EIE0 + i * 2);
+#ifdef CONFIG_32BIT
+			eix->eip[1] = imsic_eix_read(IMSIC_EIP0 + i * 2 + 1);
+			eix->eie[1] = imsic_eix_read(IMSIC_EIE0 + i * 2 + 1);
+#endif
+		}
+	}
+
+	csr_write(CSR_HSTATUS, old_hstatus);
+	csr_write(CSR_VSISELECT, old_vsiselect);
+}
+
+static void imsic_vsfile_read(int vsfile_hgei, int vsfile_cpu, u32 nr_eix,
+			      bool clear, struct imsic_mrif *mrif)
+{
+	struct imsic_vsfile_read_data idata;
+
+	/* We can only read clear if we have a IMSIC VS-file */
+	if (vsfile_cpu < 0 || vsfile_hgei <= 0)
+		return;
+
+	/* We can only read clear on local CPU */
+	idata.hgei = vsfile_hgei;
+	idata.nr_eix = nr_eix;
+	idata.clear = clear;
+	idata.mrif = mrif;
+	on_each_cpu_mask(cpumask_of(vsfile_cpu),
+			 imsic_vsfile_local_read, &idata, 1);
+}
+
+static void imsic_vsfile_local_clear(int vsfile_hgei, u32 nr_eix)
+{
+	u32 i;
+	unsigned long new_hstatus, old_hstatus, old_vsiselect;
+
+	/* We can only zero-out if we have a IMSIC VS-file */
+	if (vsfile_hgei <= 0)
+		return;
+
+	old_vsiselect = csr_read(CSR_VSISELECT);
+	old_hstatus = csr_read(CSR_HSTATUS);
+	new_hstatus = old_hstatus & ~HSTATUS_VGEIN;
+	new_hstatus |= ((unsigned long)vsfile_hgei) << HSTATUS_VGEIN_SHIFT;
+	csr_write(CSR_HSTATUS, new_hstatus);
+
+	imsic_vs_csr_write(IMSIC_EIDELIVERY, 0);
+	imsic_vs_csr_write(IMSIC_EITHRESHOLD, 0);
+	for (i = 0; i < nr_eix; i++) {
+		imsic_eix_write(IMSIC_EIP0 + i * 2, 0);
+		imsic_eix_write(IMSIC_EIE0 + i * 2, 0);
+#ifdef CONFIG_32BIT
+		imsic_eix_write(IMSIC_EIP0 + i * 2 + 1, 0);
+		imsic_eix_write(IMSIC_EIE0 + i * 2 + 1, 0);
+#endif
+	}
+
+	csr_write(CSR_HSTATUS, old_hstatus);
+	csr_write(CSR_VSISELECT, old_vsiselect);
+}
+
+static void imsic_vsfile_local_update(int vsfile_hgei, u32 nr_eix,
+				      struct imsic_mrif *mrif)
+{
+	u32 i;
+	struct imsic_mrif_eix *eix;
+	unsigned long new_hstatus, old_hstatus, old_vsiselect;
+
+	/* We can only update if we have a HW IMSIC context */
+	if (vsfile_hgei <= 0)
+		return;
+
+	/*
+	 * We don't use imsic_mrif_atomic_xyz() functions to read values
+	 * from MRIF in this function because it is always called with
+	 * pointer to temporary MRIF on stack.
+	 */
+
+	old_vsiselect = csr_read(CSR_VSISELECT);
+	old_hstatus = csr_read(CSR_HSTATUS);
+	new_hstatus = old_hstatus & ~HSTATUS_VGEIN;
+	new_hstatus |= ((unsigned long)vsfile_hgei) << HSTATUS_VGEIN_SHIFT;
+	csr_write(CSR_HSTATUS, new_hstatus);
+
+	for (i = 0; i < nr_eix; i++) {
+		eix = &mrif->eix[i];
+		imsic_eix_set(IMSIC_EIP0 + i * 2, eix->eip[0]);
+		imsic_eix_set(IMSIC_EIE0 + i * 2, eix->eie[0]);
+#ifdef CONFIG_32BIT
+		imsic_eix_set(IMSIC_EIP0 + i * 2 + 1, eix->eip[1]);
+		imsic_eix_set(IMSIC_EIE0 + i * 2 + 1, eix->eie[1]);
+#endif
+	}
+	imsic_vs_csr_write(IMSIC_EITHRESHOLD, mrif->eithreshold);
+	imsic_vs_csr_write(IMSIC_EIDELIVERY, mrif->eidelivery);
+
+	csr_write(CSR_HSTATUS, old_hstatus);
+	csr_write(CSR_VSISELECT, old_vsiselect);
+}
+
+static void imsic_vsfile_cleanup(struct imsic *imsic)
+{
+	int old_vsfile_hgei, old_vsfile_cpu;
+	unsigned long flags;
+
+	/*
+	 * We don't use imsic_mrif_atomic_xyz() functions to clear the
+	 * SW-file in this function because it is always called when the
+	 * VCPU is being destroyed.
+	 */
+
+	write_lock_irqsave(&imsic->vsfile_lock, flags);
+	old_vsfile_hgei = imsic->vsfile_hgei;
+	old_vsfile_cpu = imsic->vsfile_cpu;
+	imsic->vsfile_cpu = imsic->vsfile_hgei = -1;
+	imsic->vsfile_va = NULL;
+	imsic->vsfile_pa = 0;
+	write_unlock_irqrestore(&imsic->vsfile_lock, flags);
+
+	memset(imsic->swfile, 0, sizeof(*imsic->swfile));
+
+	if (old_vsfile_cpu >= 0)
+		kvm_riscv_aia_free_hgei(old_vsfile_cpu, old_vsfile_hgei);
+}
+
+static void imsic_swfile_extirq_update(struct kvm_vcpu *vcpu)
+{
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+	struct imsic_mrif *mrif = imsic->swfile;
+
+	if (imsic_mrif_atomic_read(mrif, &mrif->eidelivery) &&
+	    imsic_mrif_topei(mrif, imsic->nr_eix, imsic->nr_msis))
+		kvm_riscv_vcpu_set_interrupt(vcpu, IRQ_VS_EXT);
+	else
+		kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_EXT);
+}
+
+static void imsic_swfile_read(struct kvm_vcpu *vcpu, bool clear,
+			      struct imsic_mrif *mrif)
+{
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+
+	/*
+	 * We don't use imsic_mrif_atomic_xyz() functions to read and
+	 * write SW-file and MRIF in this function because it is always
+	 * called when VCPU is not using SW-file and the MRIF points to
+	 * a temporary MRIF on stack.
+	 */
+
+	memcpy(mrif, imsic->swfile, sizeof(*mrif));
+	if (clear) {
+		memset(imsic->swfile, 0, sizeof(*imsic->swfile));
+		kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_EXT);
+	}
+}
+
+static void imsic_swfile_update(struct kvm_vcpu *vcpu,
+				struct imsic_mrif *mrif)
+{
+	u32 i;
+	struct imsic_mrif_eix *seix, *eix;
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+	struct imsic_mrif *smrif = imsic->swfile;
+
+	imsic_mrif_atomic_write(smrif, &smrif->eidelivery, mrif->eidelivery);
+	imsic_mrif_atomic_write(smrif, &smrif->eithreshold, mrif->eithreshold);
+	for (i = 0; i < imsic->nr_eix; i++) {
+		seix = &smrif->eix[i];
+		eix = &mrif->eix[i];
+		imsic_mrif_atomic_or(smrif, &seix->eip[0], eix->eip[0]);
+		imsic_mrif_atomic_or(smrif, &seix->eie[0], eix->eie[0]);
+#ifdef CONFIG_32BIT
+		imsic_mrif_atomic_or(smrif, &seix->eip[1], eix->eip[1]);
+		imsic_mrif_atomic_or(smrif, &seix->eie[1], eix->eie[1]);
+#endif
+	}
+
+	imsic_swfile_extirq_update(vcpu);
+}
+
+void kvm_riscv_vcpu_aia_imsic_release(struct kvm_vcpu *vcpu)
+{
+	unsigned long flags;
+	struct imsic_mrif tmrif;
+	int old_vsfile_hgei, old_vsfile_cpu;
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+
+	/* Read and clear IMSIC VS-file details */
+	write_lock_irqsave(&imsic->vsfile_lock, flags);
+	old_vsfile_hgei = imsic->vsfile_hgei;
+	old_vsfile_cpu = imsic->vsfile_cpu;
+	imsic->vsfile_cpu = imsic->vsfile_hgei = -1;
+	imsic->vsfile_va = NULL;
+	imsic->vsfile_pa = 0;
+	write_unlock_irqrestore(&imsic->vsfile_lock, flags);
+
+	/* Do nothing, if no IMSIC VS-file to release */
+	if (old_vsfile_cpu < 0)
+		return;
+
+	/*
+	 * At this point, all interrupt producers are still using
+	 * the old IMSIC VS-file so we first re-direct all interrupt
+	 * producers.
+	 */
+
+	/* Purge the G-stage mapping */
+	kvm_riscv_gstage_iounmap(vcpu->kvm,
+				 vcpu->arch.aia_context.imsic_addr,
+				 IMSIC_MMIO_PAGE_SZ);
+
+	/* TODO: Purge the IOMMU mapping ??? */
+
+	/*
+	 * At this point, all interrupt producers have been re-directed
+	 * to somewhere else so we move register state from the old IMSIC
+	 * VS-file to the IMSIC SW-file.
+	 */
+
+	/* Read and clear register state from old IMSIC VS-file */
+	memset(&tmrif, 0, sizeof(tmrif));
+	imsic_vsfile_read(old_vsfile_hgei, old_vsfile_cpu, imsic->nr_hw_eix,
+			  true, &tmrif);
+
+	/* Update register state in IMSIC SW-file */
+	imsic_swfile_update(vcpu, &tmrif);
+
+	/* Free-up old IMSIC VS-file */
+	kvm_riscv_aia_free_hgei(old_vsfile_cpu, old_vsfile_hgei);
+}
+
+int kvm_riscv_vcpu_aia_imsic_update(struct kvm_vcpu *vcpu)
+{
+	unsigned long flags;
+	phys_addr_t new_vsfile_pa;
+	struct imsic_mrif tmrif;
+	void __iomem *new_vsfile_va;
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_run *run = vcpu->run;
+	struct kvm_vcpu_aia *vaia = &vcpu->arch.aia_context;
+	struct imsic *imsic = vaia->imsic_state;
+	int ret = 0, new_vsfile_hgei = -1, old_vsfile_hgei, old_vsfile_cpu;
+
+	/* Do nothing for emulation mode */
+	if (kvm->arch.aia.mode == KVM_DEV_RISCV_AIA_MODE_EMUL)
+		return 1;
+
+	/* Read old IMSIC VS-file details */
+	read_lock_irqsave(&imsic->vsfile_lock, flags);
+	old_vsfile_hgei = imsic->vsfile_hgei;
+	old_vsfile_cpu = imsic->vsfile_cpu;
+	read_unlock_irqrestore(&imsic->vsfile_lock, flags);
+
+	/* Do nothing if we are continuing on same CPU */
+	if (old_vsfile_cpu == vcpu->cpu)
+		return 1;
+
+	/* Allocate new IMSIC VS-file */
+	ret = kvm_riscv_aia_alloc_hgei(vcpu->cpu, vcpu,
+				       &new_vsfile_va, &new_vsfile_pa);
+	if (ret <= 0) {
+		/* For HW acceleration mode, we can't continue */
+		if (kvm->arch.aia.mode == KVM_DEV_RISCV_AIA_MODE_HWACCEL) {
+			run->fail_entry.hardware_entry_failure_reason =
+								CSR_HSTATUS;
+			run->fail_entry.cpu = vcpu->cpu;
+			run->exit_reason = KVM_EXIT_FAIL_ENTRY;
+			return 0;
+		}
+
+		/* Release old IMSIC VS-file */
+		if (old_vsfile_cpu >= 0)
+			kvm_riscv_vcpu_aia_imsic_release(vcpu);
+
+		/* For automatic mode, we continue */
+		goto done;
+	}
+	new_vsfile_hgei = ret;
+
+	/*
+	 * At this point, all interrupt producers are still using
+	 * to the old IMSIC VS-file so we first move all interrupt
+	 * producers to the new IMSIC VS-file.
+	 */
+
+	/* Zero-out new IMSIC VS-file */
+	imsic_vsfile_local_clear(new_vsfile_hgei, imsic->nr_hw_eix);
+
+	/* Update G-stage mapping for the new IMSIC VS-file */
+	ret = kvm_riscv_gstage_ioremap(kvm, vcpu->arch.aia_context.imsic_addr,
+				       new_vsfile_pa, IMSIC_MMIO_PAGE_SZ,
+				       true, true);
+	if (ret)
+		goto fail_free_vsfile_hgei;
+
+	/* TODO: Update the IOMMU mapping ??? */
+
+	/* Update new IMSIC VS-file details in IMSIC context */
+	write_lock_irqsave(&imsic->vsfile_lock, flags);
+	imsic->vsfile_hgei = new_vsfile_hgei;
+	imsic->vsfile_cpu = vcpu->cpu;
+	imsic->vsfile_va = new_vsfile_va;
+	imsic->vsfile_pa = new_vsfile_pa;
+	write_unlock_irqrestore(&imsic->vsfile_lock, flags);
+
+	/*
+	 * At this point, all interrupt producers have been moved
+	 * to the new IMSIC VS-file so we move register state from
+	 * the old IMSIC VS/SW-file to the new IMSIC VS-file.
+	 */
+
+	memset(&tmrif, 0, sizeof(tmrif));
+	if (old_vsfile_cpu >= 0) {
+		/* Read and clear register state from old IMSIC VS-file */
+		imsic_vsfile_read(old_vsfile_hgei, old_vsfile_cpu,
+				  imsic->nr_hw_eix, true, &tmrif);
+
+		/* Free-up old IMSIC VS-file */
+		kvm_riscv_aia_free_hgei(old_vsfile_cpu, old_vsfile_hgei);
+	} else {
+		/* Read and clear register state from IMSIC SW-file */
+		imsic_swfile_read(vcpu, true, &tmrif);
+	}
+
+	/* Restore register state in the new IMSIC VS-file */
+	imsic_vsfile_local_update(new_vsfile_hgei, imsic->nr_hw_eix, &tmrif);
+
+done:
+	/* Set VCPU HSTATUS.VGEIN to new IMSIC VS-file */
+	vcpu->arch.guest_context.hstatus &= ~HSTATUS_VGEIN;
+	if (new_vsfile_hgei > 0)
+		vcpu->arch.guest_context.hstatus |=
+			((unsigned long)new_vsfile_hgei) << HSTATUS_VGEIN_SHIFT;
+
+	/* Continue run-loop */
+	return 1;
+
+fail_free_vsfile_hgei:
+	kvm_riscv_aia_free_hgei(vcpu->cpu, new_vsfile_hgei);
+	return ret;
+}
+
+int kvm_riscv_vcpu_aia_imsic_rmw(struct kvm_vcpu *vcpu, unsigned long isel,
+				 unsigned long *val, unsigned long new_val,
+				 unsigned long wr_mask)
+{
+	u32 topei;
+	struct imsic_mrif_eix *eix;
+	int r, rc = KVM_INSN_CONTINUE_NEXT_SEPC;
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+
+	if (isel == KVM_RISCV_AIA_IMSIC_TOPEI) {
+		/* Read pending and enabled interrupt with highest priority */
+		topei = imsic_mrif_topei(imsic->swfile, imsic->nr_eix,
+					 imsic->nr_msis);
+		if (val)
+			*val = topei;
+
+		/* Writes ignore value and clear top pending interrupt */
+		if (topei && wr_mask) {
+			topei >>= TOPEI_ID_SHIFT;
+			if (topei) {
+				eix = &imsic->swfile->eix[topei /
+							  BITS_PER_TYPE(u64)];
+				clear_bit(topei & (BITS_PER_TYPE(u64) - 1),
+					  eix->eip);
+			}
+		}
+	} else {
+		r = imsic_mrif_rmw(imsic->swfile, imsic->nr_eix, isel,
+				   val, new_val, wr_mask);
+		/* Forward unknown IMSIC register to user-space */
+		if (r)
+			rc = (r == -ENOENT) ? 0 : KVM_INSN_ILLEGAL_TRAP;
+	}
+
+	if (wr_mask)
+		imsic_swfile_extirq_update(vcpu);
+
+	return rc;
+}
+
+void kvm_riscv_vcpu_aia_imsic_reset(struct kvm_vcpu *vcpu)
+{
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+
+	if (!imsic)
+		return;
+
+	kvm_riscv_vcpu_aia_imsic_release(vcpu);
+
+	memset(imsic->swfile, 0, sizeof(*imsic->swfile));
+}
+
+int kvm_riscv_vcpu_aia_imsic_inject(struct kvm_vcpu *vcpu,
+				    u32 guest_index, u32 offset, u32 iid)
+{
+	unsigned long flags;
+	struct imsic_mrif_eix *eix;
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+
+	/* We only emulate one IMSIC MMIO page for each Guest VCPU */
+	if (!imsic || !iid || guest_index ||
+	    (offset != IMSIC_MMIO_SETIPNUM_LE &&
+	     offset != IMSIC_MMIO_SETIPNUM_BE))
+		return -ENODEV;
+
+	iid = (offset == IMSIC_MMIO_SETIPNUM_BE) ? __swab32(iid) : iid;
+	if (imsic->nr_msis <= iid)
+		return -EINVAL;
+
+	read_lock_irqsave(&imsic->vsfile_lock, flags);
+
+	if (imsic->vsfile_cpu >= 0) {
+		writel(iid, imsic->vsfile_va + IMSIC_MMIO_SETIPNUM_LE);
+		kvm_vcpu_kick(vcpu);
+	} else {
+		eix = &imsic->swfile->eix[iid / BITS_PER_TYPE(u64)];
+		set_bit(iid & (BITS_PER_TYPE(u64) - 1), eix->eip);
+		imsic_swfile_extirq_update(vcpu);
+	}
+
+	read_unlock_irqrestore(&imsic->vsfile_lock, flags);
+
+	return 0;
+}
+
+static int imsic_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
+			   gpa_t addr, int len, void *val)
+{
+	if (len != 4 || (addr & 0x3) != 0)
+		return -EOPNOTSUPP;
+
+	*((u32 *)val) = 0;
+
+	return 0;
+}
+
+static int imsic_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
+			    gpa_t addr, int len, const void *val)
+{
+	struct kvm_msi msi = { 0 };
+
+	if (len != 4 || (addr & 0x3) != 0)
+		return -EOPNOTSUPP;
+
+	msi.address_hi = addr >> 32;
+	msi.address_lo = (u32)addr;
+	msi.data = *((const u32 *)val);
+	kvm_riscv_aia_inject_msi(vcpu->kvm, &msi);
+
+	return 0;
+};
+
+static struct kvm_io_device_ops imsic_iodoev_ops = {
+	.read = imsic_mmio_read,
+	.write = imsic_mmio_write,
+};
+
+int kvm_riscv_vcpu_aia_imsic_init(struct kvm_vcpu *vcpu)
+{
+	int ret = 0;
+	struct imsic *imsic;
+	struct page *swfile_page;
+	struct kvm *kvm = vcpu->kvm;
+
+	/* Fail if we have zero IDs */
+	if (!kvm->arch.aia.nr_ids)
+		return -EINVAL;
+
+	/* Allocate IMSIC context */
+	imsic = kzalloc(sizeof(*imsic), GFP_KERNEL);
+	if (!imsic)
+		return -ENOMEM;
+	vcpu->arch.aia_context.imsic_state = imsic;
+
+	/* Setup IMSIC context  */
+	imsic->nr_msis = kvm->arch.aia.nr_ids + 1;
+	rwlock_init(&imsic->vsfile_lock);
+	imsic->nr_eix = BITS_TO_U64(imsic->nr_msis);
+	imsic->nr_hw_eix = BITS_TO_U64(kvm_riscv_aia_max_ids);
+	imsic->vsfile_hgei = imsic->vsfile_cpu = -1;
+
+	/* Setup IMSIC SW-file */
+	swfile_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
+				  get_order(sizeof(*imsic->swfile)));
+	if (!swfile_page) {
+		ret = -ENOMEM;
+		goto fail_free_imsic;
+	}
+	imsic->swfile = page_to_virt(swfile_page);
+	imsic->swfile_pa = page_to_phys(swfile_page);
+
+	/* Setup IO device */
+	kvm_iodevice_init(&imsic->iodev, &imsic_iodoev_ops);
+	mutex_lock(&kvm->slots_lock);
+	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS,
+				      vcpu->arch.aia_context.imsic_addr,
+				      KVM_DEV_RISCV_IMSIC_SIZE,
+				      &imsic->iodev);
+	mutex_unlock(&kvm->slots_lock);
+	if (ret)
+		goto fail_free_swfile;
+
+	return 0;
+
+fail_free_swfile:
+	free_pages((unsigned long)imsic->swfile,
+		   get_order(sizeof(*imsic->swfile)));
+fail_free_imsic:
+	vcpu->arch.aia_context.imsic_state = NULL;
+	kfree(imsic);
+	return ret;
+}
+
+void kvm_riscv_vcpu_aia_imsic_cleanup(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct imsic *imsic = vcpu->arch.aia_context.imsic_state;
+
+	if (!imsic)
+		return;
+
+	imsic_vsfile_cleanup(imsic);
+
+	mutex_lock(&kvm->slots_lock);
+	kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &imsic->iodev);
+	mutex_unlock(&kvm->slots_lock);
+
+	free_pages((unsigned long)imsic->swfile,
+		   get_order(sizeof(*imsic->swfile)));
+
+	vcpu->arch.aia_context.imsic_state = NULL;
+	kfree(imsic);
+}