Commit 41f4d0cc authored by Atish Patra's avatar Atish Patra Committed by Anup Patel
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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: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarAtish Patra <atishp@rivosinc.com>
Reviewed-by: default avatarAnup Patel <anup@brainfault.org>
Acked-by: default avatarPaul Walmsley <pjw@kernel.org>
Link: https://lore.kernel.org/r/20250909-pmu_event_info-v6-6-d8f80cacb884@rivosinc.com


Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
parent 880fcc32

arch/riscv/kvm/vcpu_pmu.c

+2 −9
Original line number Diff line number Diff line
@@ -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;

	}

arch/riscv/kvm/vcpu_sbi_sta.c

+2 −7
Original line number Diff line number Diff line
@@ -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;