From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.21]) (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 CDB5037E5CD; Thu, 30 Jul 2026 02:51:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.21 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785379882; cv=none; b=JUlo1pvwZWWdWQB7l7Chxbb7jKjyCHWRUSJVg89Q9n2dOSFM4mqi/94DIZ2DlKYe2lamzNOi1jpJLvWV205r+4JgN+yEskSyob+3y3CpEpV9xFLqxhd36Iz3Tf9i06yblIo5a3arjzAEjUWQtyKocQTNN4eB9ZYhimv3WMKzOOk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785379882; c=relaxed/simple; bh=58BUX/Pc9LVGX59oowWgG9SPbEbBcMJaSGaZjjJTc3A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JzU8bcIIQ69MEQspYRk5pRfvUPs4qUPF2kTmXdqhHssyNbQqXRmnV0vuzmIb7aEjC17oOccJSd57Pw9SiRae7SLmsdYvTo9nstuN4vQ9wbjk8dSiMTaE7M7kMxOeRsISRhgZjG3u0LUuj14fMYOB4DFKNJOing+aaCSbz/j2Eaw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=H4rnyeYL; arc=none smtp.client-ip=198.175.65.21 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="H4rnyeYL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1785379881; x=1816915881; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=58BUX/Pc9LVGX59oowWgG9SPbEbBcMJaSGaZjjJTc3A=; b=H4rnyeYL8f5a/Eh/mHE4hhcghKYCsF/Zhtw49d/Mcc1bhhLXvcoXeXBv DUyZcC8M8fjdPdFNZDXfZbTgjQVUjV2VqH+A3kEDKzNVNupjsqdh8W205 6liXR4tBZzNpWRK/3wOu7hiCZxpLMPsEqrb8rgeTxqMz46JFiqkbwiW3Q z37uk5HRYRjLXbu0Cpk1SSRPSQAsg2yref/crQoqgADS502JsBnwzKH9u jALrJqvWSE1yRN3G5RoNNNBYPiHx1YCzWpw6vvtctLSGh+EfTtFmQI0tv 0BQo4zcTMmSDXCna17WurJxDuKRIkIEsmNlqRa2QXsrzjza0P1JQaazVn Q==; X-CSE-ConnectionGUID: t+Wa509yTHy9Ad0TRqFdjw== X-CSE-MsgGUID: kYhGb2rQTiyGyZYy6DYWTA== X-IronPort-AV: E=McAfee;i="6800,10657,11859"; a="85848296" X-IronPort-AV: E=Sophos;i="6.25,193,1779174000"; d="scan'208";a="85848296" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2026 19:51:20 -0700 X-CSE-ConnectionGUID: MKxZhcNeSS+14YAS31UiXg== X-CSE-MsgGUID: 6kLRLULWRIGSBKbcIQo1Jg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,193,1779174000"; d="scan'208";a="258941269" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.241.178]) ([10.124.241.178]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2026 19:51:17 -0700 Message-ID: Date: Thu, 30 Jul 2026 10:51:15 +0800 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 7/9] KVM: x86/pmu: Restrict RDPMC passthrough to known CPUs To: Zide Chen , Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, Jim Mattson , Andi Kleen , linux-kernel@vger.kernel.org, Mingwei Zhang , Das Sandipan , Shukla Manali , Falcon Thomas , Xudong Hao References: <20260727192131.582105-1-zide.chen@intel.com> <20260727192131.582105-8-zide.chen@intel.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: <20260727192131.582105-8-zide.chen@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/28/2026 3:21 AM, Zide Chen wrote: > RDPMC type encodings are vendor-defined and could theoretically be > extended on future CPUs. An unknown RDPMC type could leak host > PMU information to the guest through RDPMC passthrough. > > Rather than assuming future CPUs are safe, explicitly permit only > reviewed CPU models and require RDPMC interception everywhere else. > This ensures RDPMC passthrough is enabled only on CPUs whose RDPMC > encodings are audited and supported by KVM. > > Suggested-by: Dapeng Mi > Suggested-by: Jim Mattson > Signed-off-by: Zide Chen > --- > v7: new patch. > --- > arch/x86/kvm/pmu.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > index 51c6d00a485f..092809bd757d 100644 > --- a/arch/x86/kvm/pmu.c > +++ b/arch/x86/kvm/pmu.c > @@ -77,6 +77,21 @@ static const struct x86_cpu_id vmx_pebs_pdist_cpu[] = { > {} > }; > > +/* > + * CPUs whose RDPMC encodings have been audited for KVM RDPMC > + * passthrough support. > + */ > +static const struct x86_cpu_id kvm_rdpmc_known_cpus[] = { > + X86_MATCH_VFM(INTEL_ATOM_DARKMONT_X, NULL), > + X86_MATCH_VFM(INTEL_LUNARLAKE_M, NULL), > + X86_MATCH_VFM(INTEL_NOVALAKE, NULL), > + X86_MATCH_VFM(INTEL_NOVALAKE_L, NULL), > + X86_MATCH_VFM(INTEL_PANTHERLAKE_L, NULL), > + X86_MATCH_VFM(INTEL_PANTHERLAKE_R, NULL), > + X86_MATCH_VFM(INTEL_WILDCATLAKE_L, NULL), > + {} > +}; > + > /* NOTE: > * - Each perf counter is defined as "struct kvm_pmc"; > * - There are two types of perf counters: general purpose (gp) and fixed. > @@ -807,6 +822,20 @@ bool kvm_need_perf_global_ctrl_intercept(struct kvm_vcpu *vcpu) > } > EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_need_perf_global_ctrl_intercept); > > +static bool kvm_rdpmc_encoding_supported(void) > +{ > + /* KVM understands all RDPMC encodings prior to PMU v6. */ > + if (kvm_host_pmu.version < 6) I'm not sure if this works for AMD platforms. Jim said current AMD platforms already have security holes and I believe the PMU version of AMD platforms are less than 6. Need AMD guys to confirm. @Sandipan, @Manali. > + return true; > + > + /* > + * Future PMU v6 implementations and future PMU versions require RDPMC > + * interception until their RDPMC encodings are audited and supported > + * by KVM. > + */ > + return x86_match_cpu(kvm_rdpmc_known_cpus); x86_match_cpu() returns structure x86_cpu_id pointer or NULL instead of a boolean variable. Better explicitly covert it to a boolean variable. return x86_match_cpu(kvm_rdpmc_known_cpus) != NULL; > +} > + > bool kvm_need_rdpmc_intercept(struct kvm_vcpu *vcpu) > { > struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); > @@ -818,6 +847,9 @@ bool kvm_need_rdpmc_intercept(struct kvm_vcpu *vcpu) > if (enable_vmware_backdoor) > return true; > > + if (!kvm_rdpmc_encoding_supported()) > + return true; > + > return kvm_need_any_pmc_intercept(vcpu) || > pmu->counter_bitmask[KVM_PMC_GP] != (BIT_ULL(kvm_host_pmu.bit_width_gp) - 1) || > pmu->counter_bitmask[KVM_PMC_FIXED] != (BIT_ULL(kvm_host_pmu.bit_width_fixed) - 1);