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, 22 insertions, 13 deletions

diff --git a/arch/riscv/kvm/vcpu_sbi_v01.c b/arch/riscv/kvm/vcpu_sbi_v01.c
index da4d6c99c2cf..8a91a14e7139 100644
--- a/arch/riscv/kvm/vcpu_sbi_v01.c
+++ b/arch/riscv/kvm/vcpu_sbi_v01.c
@@ -23,7 +23,6 @@ static int kvm_sbi_ext_v01_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	int i, ret = 0;
 	u64 next_cycle;
 	struct kvm_vcpu *rvcpu;
-	struct cpumask cm;
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
 
@@ -80,19 +79,29 @@ static int kvm_sbi_ext_v01_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		if (utrap->scause)
 			break;
 
-		cpumask_clear(&cm);
-		for_each_set_bit(i, &hmask, BITS_PER_LONG) {
-			rvcpu = kvm_get_vcpu_by_id(vcpu->kvm, i);
-			if (rvcpu->cpu < 0)
-				continue;
-			cpumask_set_cpu(rvcpu->cpu, &cm);
-		}
 		if (cp->a7 == SBI_EXT_0_1_REMOTE_FENCE_I)
-			ret = sbi_remote_fence_i(&cm);
-		else if (cp->a7 == SBI_EXT_0_1_REMOTE_SFENCE_VMA)
-			ret = sbi_remote_hfence_vvma(&cm, cp->a1, cp->a2);
-		else
-			ret = sbi_remote_hfence_vvma_asid(&cm, cp->a1, cp->a2, cp->a3);
+			kvm_riscv_fence_i(vcpu->kvm, 0, hmask);
+		else if (cp->a7 == SBI_EXT_0_1_REMOTE_SFENCE_VMA) {
+			if (cp->a1 == 0 && cp->a2 == 0)
+				kvm_riscv_hfence_vvma_all(vcpu->kvm,
+							  0, hmask);
+			else
+				kvm_riscv_hfence_vvma_gva(vcpu->kvm,
+							  0, hmask,
+							  cp->a1, cp->a2,
+							  PAGE_SHIFT);
+		} else {
+			if (cp->a1 == 0 && cp->a2 == 0)
+				kvm_riscv_hfence_vvma_asid_all(vcpu->kvm,
+							       0, hmask,
+							       cp->a3);
+			else
+				kvm_riscv_hfence_vvma_asid_gva(vcpu->kvm,
+							       0, hmask,
+							       cp->a1, cp->a2,
+							       PAGE_SHIFT,
+							       cp->a3);
+		}
 		break;
 	default:
 		ret = -EINVAL;