Re: [PATCH] KVM/x86: pmu: Fix #GP condition check for RDPMC emulation

Sean Christopherson
2020-07-08T15:18:53Z

On Wed, Jul 08, 2020 at 03:44:09PM +0800, Like Xu wrote:
> in guest protected mode, if the current privilege level
> is not 0 and the pce flag in the cr4 register is cleared,
> we will inject a #gp for rdpmc usage.

Wrapping at ~58 characters is a bit aggressive. checkpatch enforces 75
chars, something near that would be prefereable.

> Signed-off-by: Like Xu <like.xu@linux.intel.com>
> ---
> arch/x86/kvm/pmu.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index b86346903f2e..d080d475c808 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -372,6 +372,11 @@ int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned idx, u64 *data)
> if (!pmc)
> return 1;
>
> + if ((kvm_x86_ops.get_cpl(vcpu) != 0) &&
> + !(kvm_read_cr4(vcpu) & X86_CR4_PCE) &&
> + (kvm_read_cr4(vcpu) & X86_CR0_PE))

This reads CR4 but checks CR0.PE.

And maybe put the X86_CR4_PCE check first so that it's the focus of the
statement?

> + return 1;
> +
> *data = pmc_read_counter(pmc) & mask;
> return 0;
> }
> --
> 2.21.3
>