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    SubjectRe: [PATCH v4 09/14] RISC-V: KVM: Make PMU functionality depend on Sscofpmf
    On Wed, Feb 01, 2023 at 03:12:45PM -0800, Atish Patra wrote:
    > The privilege mode filtering feature must be available in the host so
    > that the host can inhibit the counters while the execution is in HS mode.
    > Otherwise, the guests may have access to critical guest information.
    >
    > Reviewed-by: Anup Patel <anup@brainfault.org>
    > Signed-off-by: Atish Patra <atishp@rivosinc.com>
    > ---
    > arch/riscv/kvm/vcpu_pmu.c | 8 ++++++++
    > 1 file changed, 8 insertions(+)
    >
    > diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
    > index 2dad37f..9a531fe 100644
    > --- a/arch/riscv/kvm/vcpu_pmu.c
    > +++ b/arch/riscv/kvm/vcpu_pmu.c
    > @@ -79,6 +79,14 @@ void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
    > struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
    > struct kvm_pmc *pmc;
    >
    > + /*
    > + * PMU functionality should be only available to guests if privilege mode
    > + * filtering is available in the host. Otherwise, guest will always count
    > + * events while the execution is in hypervisor mode.
    > + */
    > + if (!riscv_isa_extension_available(NULL, SSCOFPMF))
    > + return;
    > +
    > ret = riscv_pmu_get_hpm_info(&hpm_width, &num_hw_ctrs);
    > if (ret < 0 || !hpm_width || !num_hw_ctrs)
    > return;
    > --
    > 2.25.1
    >

    Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

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