RISC-V: KVM: Add remote HFENCE functions based on VCPU requests

The generic KVM has support for VCPU requests which can be used
to do arch-specific work in the run-loop. We introduce remote
HFENCE functions which will internally use VCPU requests instead
of host SBI calls.

Advantages of doing remote HFENCEs as VCPU requests are:
1) Multiple VCPUs of a Guest may be running on different Host CPUs
   so it is not always possible to determine the Host CPU mask for
   doing Host SBI call. For example, when VCPU X wants to do HFENCE
   on VCPU Y, it is possible that VCPU Y is blocked or in user-space
   (i.e. vcpu->cpu < 0).
2) To support nested virtualization, we will be having a separate
   shadow G-stage for each VCPU and a common host G-stage for the
   entire Guest/VM. The VCPU requests based remote HFENCEs helps
   us easily synchronize the common host G-stage and shadow G-stage
   of each VCPU without any additional IPI calls.

This is also a preparatory patch for upcoming nested virtualization
support where we will be having a shadow G-stage page table for
each Guest VCPU.

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

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/riscv/kvm/vmid.c b/arch/riscv/kvm/vmid.c
index 8987e76aa6db..9f764df125db 100644
--- a/arch/riscv/kvm/vmid.c
+++ b/arch/riscv/kvm/vmid.c
@@ -11,9 +11,9 @@
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/module.h>
+#include <linux/smp.h>
 #include <linux/kvm_host.h>
 #include <asm/csr.h>
-#include <asm/sbi.h>
 
 static unsigned long vmid_version = 1;
 static unsigned long vmid_next;
@@ -63,6 +63,11 @@ bool kvm_riscv_gstage_vmid_ver_changed(struct kvm_vmid *vmid)
 			READ_ONCE(vmid_version));
 }
 
+static void __local_hfence_gvma_all(void *info)
+{
+	kvm_riscv_local_hfence_gvma_all();
+}
+
 void kvm_riscv_gstage_vmid_update(struct kvm_vcpu *vcpu)
 {
 	unsigned long i;
@@ -101,7 +106,8 @@ void kvm_riscv_gstage_vmid_update(struct kvm_vcpu *vcpu)
 		 * running, we force VM exits on all host CPUs using IPI and
 		 * flush all Guest TLBs.
 		 */
-		sbi_remote_hfence_gvma(cpu_online_mask, 0, 0);
+		on_each_cpu_mask(cpu_online_mask, __local_hfence_gvma_all,
+				 NULL, 1);
 	}
 
 	vmid->vmid = vmid_next;