RISC-V: KVM: No need of explicit writable slot check

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@google.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Acked-by: Paul Walmsley <pjw@kernel.org>
Link: https://lore.kernel.org/r/20250909-pmu_event_info-v6-6-d8f80cacb884@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 15d71a7b75ba6369b58ca28f1991ec05f46cd141..f8514086bd6b073cbba73416ab29ced80e1b520a 100644 (file)
--- 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 68486f90a61e16678e970ce76a90ba452a0d24f5..afa0545c3bcfc5cf74e4643738f77b4945969d00 100644 (file)
--- 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;