From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 533B132C65 for ; Wed, 8 Nov 2023 20:41:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="AGx9yYWs" Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D12891FEE; Wed, 8 Nov 2023 12:41:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1699476087; x=1731012087; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=5vTuv7i33xV6Xb2Jmaxi1kuydek/b7NH6zn+kDGHWj0=; b=AGx9yYWsBaB+ygcs03zOhFW5tcIWY2eqPr870dOGJv25amo1oogTAWIO ov9yih9uDBUmNXETEAwP7zGRVQPt4JI0GUdyKtb9/fOnzAFY8iX9lunu2 m6UBE8TX4HfEzYhkERvSsZC3ev3LzNvNp2f/Lc3P4w0igk/Mh8huKqBkr b4VNoHZ01AGgakeeiX12ntxcQuYkZbpuik94ephUOnOItjUD9gsRZAmDZ nTzlzRtzxIXQGlDFHbugUH1Baepi5eFbCqPDyTNb+LJFAwIAWkdd08N9t e/+8VcyB3903BxvOgQnrgDlO9WCNaL+ZJIu2PiXSL/2bITlQkPV2GfAj4 Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10888"; a="380245074" X-IronPort-AV: E=Sophos;i="6.03,287,1694761200"; d="scan'208";a="380245074" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Nov 2023 12:41:27 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.03,287,1694761200"; d="scan'208";a="4311555" Received: from linux.intel.com ([10.54.29.200]) by orviesa002.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Nov 2023 12:41:27 -0800 Received: from [10.213.166.225] (kliang2-mobl1.ccr.corp.intel.com [10.213.166.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by linux.intel.com (Postfix) with ESMTPS id 4E8BA580D4E; Wed, 8 Nov 2023 12:41:26 -0800 (PST) Message-ID: <54d1437e-dcbb-49c6-a83c-bc87da03f196@linux.intel.com> Date: Wed, 8 Nov 2023 15:41:25 -0500 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 02/19] KVM: x86/pmu: Allow programming events that match unsupported arch events Content-Language: en-US To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Dapeng Mi , Jim Mattson , Jinrong Liang , Aaron Lewis , Like Xu References: <20231108003135.546002-1-seanjc@google.com> <20231108003135.546002-3-seanjc@google.com> From: "Liang, Kan" In-Reply-To: <20231108003135.546002-3-seanjc@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2023-11-07 7:31 p.m., Sean Christopherson wrote: > Remove KVM's bogus restriction that the guest can't program an event whose > encoding matches an unsupported architectural event. The enumeration of > an architectural event only says that if a CPU supports an architectural > event, then the event can be programmed using the architectural encoding. > The enumeration does NOT say anything about the encoding when the CPU > doesn't report support the architectural event. > > Preventing the guest from counting events whose encoding happens to match > an architectural event breaks existing functionality whenever Intel adds > an architectural encoding that was *ever* used for a CPU that doesn't > enumerate support for the architectural event, even if the encoding is for > the exact same event! > > E.g. the architectural encoding for Top-Down Slots is 0x01a4. Broadwell > CPUs, which do not support the Top-Down Slots architectural event, 0x10a4 > is a valid, model-specific event. Denying guest usage of 0x01a4 if/when > KVM adds support for Top-Down slots would break any Broadwell-based guest. > > Reported-by: Kan Liang > Closes: https://lore.kernel.org/all/2004baa6-b494-462c-a11f-8104ea152c6a@linux.intel.com > Fixes: a21864486f7e ("KVM: x86/pmu: Fix available_event_types check for REF_CPU_CYCLES event") > Reviewed-by: Dapeng Mi > Reviewed-by: Jim Mattson > Signed-off-by: Sean Christopherson > --- Reviewed-by: Kan Liang Thanks, Kan > arch/x86/include/asm/kvm-x86-pmu-ops.h | 1 - > arch/x86/kvm/pmu.c | 1 - > arch/x86/kvm/pmu.h | 1 - > arch/x86/kvm/svm/pmu.c | 6 ---- > arch/x86/kvm/vmx/pmu_intel.c | 38 -------------------------- > 5 files changed, 47 deletions(-) > > diff --git a/arch/x86/include/asm/kvm-x86-pmu-ops.h b/arch/x86/include/asm/kvm-x86-pmu-ops.h > index 6c98f4bb4228..884af8ef7657 100644 > --- a/arch/x86/include/asm/kvm-x86-pmu-ops.h > +++ b/arch/x86/include/asm/kvm-x86-pmu-ops.h > @@ -12,7 +12,6 @@ BUILD_BUG_ON(1) > * a NULL definition, for example if "static_call_cond()" will be used > * at the call sites. > */ > -KVM_X86_PMU_OP(hw_event_available) > KVM_X86_PMU_OP(pmc_idx_to_pmc) > KVM_X86_PMU_OP(rdpmc_ecx_to_pmc) > KVM_X86_PMU_OP(msr_idx_to_pmc) > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > index 9ae07db6f0f6..99ed72966528 100644 > --- a/arch/x86/kvm/pmu.c > +++ b/arch/x86/kvm/pmu.c > @@ -374,7 +374,6 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc) > static bool pmc_event_is_allowed(struct kvm_pmc *pmc) > { > return pmc_is_globally_enabled(pmc) && pmc_speculative_in_use(pmc) && > - static_call(kvm_x86_pmu_hw_event_available)(pmc) && > check_pmu_event_filter(pmc); > } > > diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h > index 1d64113de488..10fe5bf02705 100644 > --- a/arch/x86/kvm/pmu.h > +++ b/arch/x86/kvm/pmu.h > @@ -19,7 +19,6 @@ > #define VMWARE_BACKDOOR_PMC_APPARENT_TIME 0x10002 > > struct kvm_pmu_ops { > - bool (*hw_event_available)(struct kvm_pmc *pmc); > struct kvm_pmc *(*pmc_idx_to_pmc)(struct kvm_pmu *pmu, int pmc_idx); > struct kvm_pmc *(*rdpmc_ecx_to_pmc)(struct kvm_vcpu *vcpu, > unsigned int idx, u64 *mask); > diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c > index 373ff6a6687b..5596fe816ea8 100644 > --- a/arch/x86/kvm/svm/pmu.c > +++ b/arch/x86/kvm/svm/pmu.c > @@ -73,11 +73,6 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr, > return amd_pmc_idx_to_pmc(pmu, idx); > } > > -static bool amd_hw_event_available(struct kvm_pmc *pmc) > -{ > - return true; > -} > - > static bool amd_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx) > { > struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > @@ -249,7 +244,6 @@ static void amd_pmu_reset(struct kvm_vcpu *vcpu) > } > > struct kvm_pmu_ops amd_pmu_ops __initdata = { > - .hw_event_available = amd_hw_event_available, > .pmc_idx_to_pmc = amd_pmc_idx_to_pmc, > .rdpmc_ecx_to_pmc = amd_rdpmc_ecx_to_pmc, > .msr_idx_to_pmc = amd_msr_idx_to_pmc, > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c > index c6e227edcf8e..7737ee2fc62f 100644 > --- a/arch/x86/kvm/vmx/pmu_intel.c > +++ b/arch/x86/kvm/vmx/pmu_intel.c > @@ -101,43 +101,6 @@ static struct kvm_pmc *intel_pmc_idx_to_pmc(struct kvm_pmu *pmu, int pmc_idx) > } > } > > -static bool intel_hw_event_available(struct kvm_pmc *pmc) > -{ > - struct kvm_pmu *pmu = pmc_to_pmu(pmc); > - u8 event_select = pmc->eventsel & ARCH_PERFMON_EVENTSEL_EVENT; > - u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8; > - int i; > - > - /* > - * Fixed counters are always available if KVM reaches this point. If a > - * fixed counter is unsupported in hardware or guest CPUID, KVM doesn't > - * allow the counter's corresponding MSR to be written. KVM does use > - * architectural events to program fixed counters, as the interface to > - * perf doesn't allow requesting a specific fixed counter, e.g. perf > - * may (sadly) back a guest fixed PMC with a general purposed counter. > - * But if _hardware_ doesn't support the associated event, KVM simply > - * doesn't enumerate support for the fixed counter. > - */ > - if (pmc_is_fixed(pmc)) > - return true; > - > - BUILD_BUG_ON(ARRAY_SIZE(intel_arch_events) != NR_INTEL_ARCH_EVENTS); > - > - /* > - * Disallow events reported as unavailable in guest CPUID. Note, this > - * doesn't apply to pseudo-architectural events (see above). > - */ > - for (i = 0; i < NR_REAL_INTEL_ARCH_EVENTS; i++) { > - if (intel_arch_events[i].eventsel != event_select || > - intel_arch_events[i].unit_mask != unit_mask) > - continue; > - > - return pmu->available_event_types & BIT(i); > - } > - > - return true; > -} > - > static bool intel_is_valid_rdpmc_ecx(struct kvm_vcpu *vcpu, unsigned int idx) > { > struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > @@ -802,7 +765,6 @@ void intel_pmu_cross_mapped_check(struct kvm_pmu *pmu) > } > > struct kvm_pmu_ops intel_pmu_ops __initdata = { > - .hw_event_available = intel_hw_event_available, > .pmc_idx_to_pmc = intel_pmc_idx_to_pmc, > .rdpmc_ecx_to_pmc = intel_rdpmc_ecx_to_pmc, > .msr_idx_to_pmc = intel_msr_idx_to_pmc,