From afd5dde9a186b8fc5742fff707f184760c4af1a9 Mon Sep 17 00:00:00 2001
From: Andrew Jones <ajones@ventanamicro.com>
Date: Sun, 2 Oct 2022 10:18:59 +0530
Subject: RISC-V: KVM: Provide UAPI for Zicbom block size

We're about to allow guests to use the Zicbom extension. KVM
userspace needs to know the cache block size in order to
properly advertise it to the guest. Provide a virtual config
register for userspace to get it with the GET_ONE_REG API, but
setting it cannot be supported, so disallow SET_ONE_REG.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/include/uapi/asm/kvm.h | 1 +
 arch/riscv/kvm/vcpu.c             | 8 ++++++++
 arch/riscv/mm/dma-noncoherent.c   | 2 ++
 3 files changed, 11 insertions(+)

(limited to 'arch/riscv')

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 9085b90cf324..3d7771300567 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -48,6 +48,7 @@ struct kvm_sregs {
 /* CONFIG registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
 struct kvm_riscv_config {
 	unsigned long isa;
+	unsigned long zicbom_block_size;
 };
 
 /* CORE registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 61fe1604e8ea..b0a0ce6d16ef 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -18,6 +18,7 @@
 #include <linux/fs.h>
 #include <linux/kvm_host.h>
 #include <asm/csr.h>
+#include <asm/cacheflush.h>
 #include <asm/hwcap.h>
 
 const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
@@ -261,6 +262,11 @@ static int kvm_riscv_vcpu_get_reg_config(struct kvm_vcpu *vcpu,
 	case KVM_REG_RISCV_CONFIG_REG(isa):
 		reg_val = vcpu->arch.isa[0] & KVM_RISCV_BASE_ISA_MASK;
 		break;
+	case KVM_REG_RISCV_CONFIG_REG(zicbom_block_size):
+		if (!riscv_isa_extension_available(vcpu->arch.isa, ZICBOM))
+			return -EINVAL;
+		reg_val = riscv_cbom_block_size;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -318,6 +324,8 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
 			return -EOPNOTSUPP;
 		}
 		break;
+	case KVM_REG_RISCV_CONFIG_REG(zicbom_block_size):
+		return -EOPNOTSUPP;
 	default:
 		return -EINVAL;
 	}
diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
index e3f9bdf47c5f..b0add983530a 100644
--- a/arch/riscv/mm/dma-noncoherent.c
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -13,6 +13,8 @@
 #include <asm/cacheflush.h>
 
 unsigned int riscv_cbom_block_size;
+EXPORT_SYMBOL_GPL(riscv_cbom_block_size);
+
 static bool noncoherent_supported;
 
 void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
-- 
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