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Re: [RFC PATCH 22/22] x86/AMD: add IRPerf support
- To: Edwin Török <edwin.torok@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 22 Jul 2024 15:50:34 +0200
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- Cc: Edwin Török <edvin.torok@xxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 22 Jul 2024 13:50:44 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.10.2023 21:29, Edwin Török wrote:
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -584,6 +584,13 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t
> val)
> }
> break;
>
> + case MSR_K8_HWCR:
> + if ( !(cp->x86_vendor & X86_VENDOR_AMD) ||
> + (val & ~K8_HWCR_IRPERF_EN) ||
> + wrmsr_safe(msr, val) != 0 )
> + goto gp_fault;
> + break;
Well, no: There's no-where you ever turn the bit off again. There's no
respective adjustment to guest_rdmsr(). There's no migration of the bit
guests gain control of. You also shouldn't permit writing the bit when
the feature flag is clear.
> --- a/xen/include/public/arch-x86/cpufeatureset.h
> +++ b/xen/include/public/arch-x86/cpufeatureset.h
> @@ -241,7 +241,7 @@ XEN_CPUFEATURE(EFRO, 7*32+10) /* APERF/MPERF
> Read Only interface */
>
> /* AMD-defined CPU features, CPUID level 0x80000008.ebx, word 8 */
> XEN_CPUFEATURE(CLZERO, 8*32+ 0) /*A CLZERO instruction */
> -XEN_CPUFEATURE(IRPERF, 8*32+ 1) /* Instruction Retired Performance
> Counter */
> +XEN_CPUFEATURE(IRPERF, 8*32+ 1) /*A! Instruction Retired Performance
> Counter */
Again I don't see why you have ! here. There's also missing movement of code
the previous patch added to recalculate_misc(), which now ought to be in
calculate_host_policy().
Jan
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