Correct the logic in intel_pmu_set_msr() for fixed and general purpose
counters. This was recently changed to set pmc->counter without taking
in to account the value of pmc_read_counter() which will be incorrect if
the counter is currently running and non-zero; this changes back to the
old logic which accounted for the value of currently running counters.
Signed-off-by: Eric Hankland <[email protected]>
---
arch/x86/kvm/vmx/pmu_intel.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 34a3a17bb6d7..9bdbe05b599c 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -264,9 +264,10 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
pmc->counter = data;
else
pmc->counter = (s32)data;
+ pmc->counter += pmc->counter - pmc_read_counter(pmc);
return 0;
} else if ((pmc = get_fixed_pmc(pmu, msr))) {
- pmc->counter = data;
+ pmc->counter += data - pmc_read_counter(pmc);
return 0;
} else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) {
if (data == pmc->eventsel)
On Mon, Jan 27, 2020 at 1:23 PM Eric Hankland <[email protected]> wrote:
>
> Correct the logic in intel_pmu_set_msr() for fixed and general purpose
> counters. This was recently changed to set pmc->counter without taking
> in to account the value of pmc_read_counter() which will be incorrect if
> the counter is currently running and non-zero; this changes back to the
> old logic which accounted for the value of currently running counters.
>
> Signed-off-by: Eric Hankland <[email protected]>
Fixes: 2924b52117b2 ("KVM: x86/pmu: do not mask the value that is
written to fixed PMUs")
Reviewed-by: Jim Mattson <[email protected]>
On 27/01/20 22:22, Eric Hankland wrote:
> Correct the logic in intel_pmu_set_msr() for fixed and general purpose
> counters. This was recently changed to set pmc->counter without taking
> in to account the value of pmc_read_counter() which will be incorrect if
> the counter is currently running and non-zero; this changes back to the
> old logic which accounted for the value of currently running counters.
>
> Signed-off-by: Eric Hankland <[email protected]>
> ---
> arch/x86/kvm/vmx/pmu_intel.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index 34a3a17bb6d7..9bdbe05b599c 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -264,9 +264,10 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> pmc->counter = data;
> else
> pmc->counter = (s32)data;
> + pmc->counter += pmc->counter - pmc_read_counter(pmc);
I think this best written as it was before commit 2924b52117:
if (!msr_info->host_initiated)
data = (s64)(s32)data;
pmc->counter += data - pmc_read_counter(pmc);
Do you have a testcase?
Paolo
> return 0;
> } else if ((pmc = get_fixed_pmc(pmu, msr))) {
> - pmc->counter = data;
> + pmc->counter += data - pmc_read_counter(pmc);
> return 0;
> } else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) {
> if (data == pmc->eventsel)
>
Sorry - I forgot to switch to plain text mode on my first reply.
> I think this best written as it was before commit 2924b52117:
>
> if (!msr_info->host_initiated)
> data = (s64)(s32)data;
> pmc->counter += data - pmc_read_counter(pmc);
Sounds good to me.
> Do you have a testcase?
I added a testcase to kvm-unit-tests/x86/pmu.c that fails without this
patch and passes with it.
Should I send out that patch now?
On 30/01/20 02:09, Eric Hankland wrote:
> Sorry - I forgot to switch to plain text mode on my first reply.
>
>> I think this best written as it was before commit 2924b52117:
>>
>> if (!msr_info->host_initiated)
>> data = (s64)(s32)data;
>> pmc->counter += data - pmc_read_counter(pmc);
> Sounds good to me.
>
>> Do you have a testcase?
> I added a testcase to kvm-unit-tests/x86/pmu.c that fails without this
> patch and passes with it. Should I send out that patch now?
Yes, please send it! Thanks,
Paolo
> Yes, please send it! Thanks,
I sent out the test a couple days ago and you queued it (commit
b9624f3f34bd "Test WRMSR on a running counter").
Are there any other changes that I should make?
Thanks,
Eric
On 07/02/20 23:15, Eric Hankland wrote:
>> Yes, please send it! Thanks,
>
> I sent out the test a couple days ago and you queued it (commit
> b9624f3f34bd "Test WRMSR on a running counter").
> Are there any other changes that I should make?
Nope, thanks!
Paolo