[PATCH v6 6/8] RISC-V: KVM: No need of explicit writable slot check

[Atish Patra]

There is not much value in checking if a memslot is writable explicitly
before a write as it may change underneath after the check. Rather, return
invalid address error when write_guest fails as it checks if the slot
is writable anyways.

Suggested-by: Sean Christopherson <seanjc at google.com>
Signed-off-by: Atish Patra <atishp at rivosinc.com>
---
 arch/riscv/kvm/vcpu_pmu.c     | 11 ++---------
 arch/riscv/kvm/vcpu_sbi_sta.c |  9 ++-------
 2 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 15d71a7b75ba..f8514086bd6b 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -409,8 +409,6 @@ int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long s
 	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
 	int sbiret = 0;
 	gpa_t saddr;
-	unsigned long hva;
-	bool writable;
 
 	if (!kvpmu || flags) {
 		sbiret = SBI_ERR_INVALID_PARAM;
@@ -432,19 +430,14 @@ int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long s
 		goto out;
 	}
 
-	hva = kvm_vcpu_gfn_to_hva_prot(vcpu, saddr >> PAGE_SHIFT, &writable);
-	if (kvm_is_error_hva(hva) || !writable) {
-		sbiret = SBI_ERR_INVALID_ADDRESS;
-		goto out;
-	}
-
 	kvpmu->sdata = kzalloc(snapshot_area_size, GFP_ATOMIC);
 	if (!kvpmu->sdata)
 		return -ENOMEM;
 
+	/* No need to check writable slot explicitly as kvm_vcpu_write_guest does it internally */
 	if (kvm_vcpu_write_guest(vcpu, saddr, kvpmu->sdata, snapshot_area_size)) {
 		kfree(kvpmu->sdata);
-		sbiret = SBI_ERR_FAILURE;
+		sbiret = SBI_ERR_INVALID_ADDRESS;
 		goto out;
 	}
 
diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
index cc6cb7c8f0e4..caaa28460ca4 100644
--- a/arch/riscv/kvm/vcpu_sbi_sta.c
+++ b/arch/riscv/kvm/vcpu_sbi_sta.c
@@ -85,8 +85,6 @@ static int kvm_sbi_sta_steal_time_set_shmem(struct kvm_vcpu *vcpu)
 	unsigned long shmem_phys_hi = cp->a1;
 	u32 flags = cp->a2;
 	struct sbi_sta_struct zero_sta = {0};
-	unsigned long hva;
-	bool writable;
 	gpa_t shmem;
 	int ret;
 
@@ -111,13 +109,10 @@ static int kvm_sbi_sta_steal_time_set_shmem(struct kvm_vcpu *vcpu)
 			return SBI_ERR_INVALID_ADDRESS;
 	}
 
-	hva = kvm_vcpu_gfn_to_hva_prot(vcpu, shmem >> PAGE_SHIFT, &writable);
-	if (kvm_is_error_hva(hva) || !writable)
-		return SBI_ERR_INVALID_ADDRESS;
-
+	/* No need to check writable slot explicitly as kvm_vcpu_write_guest does it internally */
 	ret = kvm_vcpu_write_guest(vcpu, shmem, &zero_sta, sizeof(zero_sta));
 	if (ret)
-		return SBI_ERR_FAILURE;
+		return SBI_ERR_INVALID_ADDRESS;
 
 	vcpu->arch.sta.shmem = shmem;
 	vcpu->arch.sta.last_steal = current->sched_info.run_delay;

-- 
2.43.0