linux-kernel - Re: [PATCH v5 17/44] KVM: x86/pmu: Snapshot host (i.e. perf's) reported PMU capabilities

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ebd33ad5-6a22-4155-9525-87937ee3c4e2@amd.com>
Date: Wed, 13 Aug 2025 15:26:28 +0530
From: Sandipan Das <sandipan.das@....com>
To: Sean Christopherson <seanjc@...gle.com>, Marc Zyngier <maz@...nel.org>,
 Oliver Upton <oliver.upton@...ux.dev>, Tianrui Zhao
 <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>, Anup Patel <anup@...infault.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Xin Li <xin@...or.com>, "H. Peter Anvin" <hpa@...or.com>,
 Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Kan Liang <kan.liang@...ux.intel.com>, Yongwei Ma <yongwei.ma@...el.com>,
 Mingwei Zhang <mizhang@...gle.com>,
 Xiong Zhang <xiong.y.zhang@...ux.intel.com>,
 Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: Re: [PATCH v5 17/44] KVM: x86/pmu: Snapshot host (i.e. perf's)
 reported PMU capabilities

On 07-08-2025 01:26, Sean Christopherson wrote:
> Take a snapshot of the unadulterated PMU capabilities provided by perf so
> that KVM can compare guest vPMU capabilities against hardware capabilities
> when determining whether or not to intercept PMU MSRs (and RDPMC).
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/pmu.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index 3206412a35a1..0f3e011824ed 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -26,6 +26,10 @@
>  /* This is enough to filter the vast majority of currently defined events. */
>  #define KVM_PMU_EVENT_FILTER_MAX_EVENTS 300
>  
> +/* Unadultered PMU capabilities of the host, i.e. of hardware. */
> +static struct x86_pmu_capability __read_mostly kvm_host_pmu;
> +
> +/* KVM's PMU capabilities, i.e. the intersection of KVM and hardware support. */
>  struct x86_pmu_capability __read_mostly kvm_pmu_cap;
>  EXPORT_SYMBOL_GPL(kvm_pmu_cap);
>  
> @@ -104,6 +108,8 @@ void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops)
>  	bool is_intel = boot_cpu_data.x86_vendor == X86_VENDOR_INTEL;
>  	int min_nr_gp_ctrs = pmu_ops->MIN_NR_GP_COUNTERS;
>  
> +	perf_get_x86_pmu_capability(&kvm_host_pmu);
> +
>  	/*
>  	 * Hybrid PMUs don't play nice with virtualization without careful
>  	 * configuration by userspace, and KVM's APIs for reporting supported
> @@ -114,18 +120,16 @@ void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops)
>  		enable_pmu = false;
>  
>  	if (enable_pmu) {
> -		perf_get_x86_pmu_capability(&kvm_pmu_cap);
> -
>  		/*
>  		 * WARN if perf did NOT disable hardware PMU if the number of
>  		 * architecturally required GP counters aren't present, i.e. if
>  		 * there are a non-zero number of counters, but fewer than what
>  		 * is architecturally required.
>  		 */
> -		if (!kvm_pmu_cap.num_counters_gp ||
> -		    WARN_ON_ONCE(kvm_pmu_cap.num_counters_gp < min_nr_gp_ctrs))
> +		if (!kvm_host_pmu.num_counters_gp ||
> +		    WARN_ON_ONCE(kvm_host_pmu.num_counters_gp < min_nr_gp_ctrs))
>  			enable_pmu = false;
> -		else if (is_intel && !kvm_pmu_cap.version)
> +		else if (is_intel && !kvm_host_pmu.version)
>  			enable_pmu = false;
>  	}
>  
> @@ -134,6 +138,7 @@ void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops)
>  		return;
>  	}
>  
> +	memcpy(&kvm_pmu_cap, &kvm_host_pmu, sizeof(kvm_host_pmu));
>  	kvm_pmu_cap.version = min(kvm_pmu_cap.version, 2);
>  	kvm_pmu_cap.num_counters_gp = min(kvm_pmu_cap.num_counters_gp,
>  					  pmu_ops->MAX_NR_GP_COUNTERS);

Reviewed-by: Sandipan Das <sandipan.das@....com>