2023-11-04 00:02:51

by Sean Christopherson

Subject: [PATCH v6 01/20] KVM: x86/pmu: Don't allow exposing unsupported architectural events

Hide architectural events that unsupported according to guest CPUID *or*
hardware, i.e. don't let userspace advertise and potentially program
unsupported architectural events.

Note, KVM already limits the length of the reverse polarity field, only
the mask itself is missing.

Fixes: f5132b01386b ("KVM: Expose a version 2 architectural PMU to a guests")
Cc: [email protected]
Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/vmx/pmu_intel.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 820d3e1f6b4f..1b13a472e3f2 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -533,7 +533,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1;
eax.split.mask_length = min_t(int, eax.split.mask_length,
kvm_pmu_cap.events_mask_len);
- pmu->available_event_types = ~entry->ebx &
+ pmu->available_event_types = ~(entry->ebx | kvm_pmu_cap.events_mask) &
((1ull << eax.split.mask_length) - 1);

if (pmu->version == 1) {
--
2.42.0.869.gea05f2083d-goog

2023-11-04 12:08:45

by Jim Mattson

Subject: Re: [PATCH v6 01/20] KVM: x86/pmu: Don't allow exposing unsupported architectural events

On Fri, Nov 3, 2023 at 5:02 PM Sean Christopherson <[email protected]> wrote:
>
> Hide architectural events that unsupported according to guest CPUID *or*
> hardware, i.e. don't let userspace advertise and potentially program
> unsupported architectural events.

The bitmask, pmu->available_event_types, is only used in
intel_hw_event_available(). As discussed
(https://lore.kernel.org/kvm/[email protected]/),
intel_hw_event_available() should go away.

> Note, KVM already limits the length of the reverse polarity field, only
> the mask itself is missing.
>
> Fixes: f5132b01386b ("KVM: Expose a version 2 architectural PMU to a guests")
> Cc: [email protected]
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/vmx/pmu_intel.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index 820d3e1f6b4f..1b13a472e3f2 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -533,7 +533,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
> pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1;
> eax.split.mask_length = min_t(int, eax.split.mask_length,
> kvm_pmu_cap.events_mask_len);
> - pmu->available_event_types = ~entry->ebx &
> + pmu->available_event_types = ~(entry->ebx | kvm_pmu_cap.events_mask) &
> ((1ull << eax.split.mask_length) - 1);
>
> if (pmu->version == 1) {
> --
> 2.42.0.869.gea05f2083d-goog
>

2023-11-06 14:43:44

by Sean Christopherson

Subject: Re: [PATCH v6 01/20] KVM: x86/pmu: Don't allow exposing unsupported architectural events

On Sat, Nov 04, 2023, Jim Mattson wrote:
> On Fri, Nov 3, 2023 at 5:02 PM Sean Christopherson <[email protected]> wrote:
> >
> > Hide architectural events that unsupported according to guest CPUID *or*
> > hardware, i.e. don't let userspace advertise and potentially program
> > unsupported architectural events.
>
> The bitmask, pmu->available_event_types, is only used in
> intel_hw_event_available(). As discussed
> (https://lore.kernel.org/kvm/[email protected]/),
> intel_hw_event_available() should go away.

Ah drat, I completely forgot about this patch when I added the patch to remove
intel_hw_event_available().