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From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
	"Jiri Olsa" <jolsa@redhat.com>,
	"Namhyung Kim" <namhyung@kernel.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Sean Christopherson" <sean.j.christopherson@intel.com>,
	"Vitaly Kuznetsov" <vkuznets@redhat.com>,
	"Wanpeng Li" <wanpengli@tencent.com>,
	"Jim Mattson" <jmattson@google.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Tony Luck" <tony.luck@intel.com>,
	"Tony W Wang-oc" <TonyWWang-oc@zhaoxin.com>,
	"Jacob Pan" <jacob.jun.pan@linux.intel.com>,
	"Len Brown" <lenb@kernel.org>, "Shuah Khan" <shuah@kernel.org>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	linux-edac@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kselftest@vger.kernel.org, "Borislav Petkov" <bp@suse.de>,
	"Jarkko Sakkinen" <jarkko.sakkinen@linux.intel.com>
Subject: [PATCH v5 13/19] x86/cpufeatures: Add flag to track whether MSR IA32_FEAT_CTL is configured
Date: Fri, 20 Dec 2019 20:45:07 -0800
Message-ID: <20191221044513.21680-14-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20191221044513.21680-1-sean.j.christopherson@intel.com>

Add a new feature flag, X86_FEATURE_MSR_IA32_FEAT_CTL, to track whether
IA32_FEAT_CTL has been initialized.  This will allow KVM, and any future
subsystems that depend on IA32_FEAT_CTL, to rely purely on cpufeatures
to query platform support, e.g. allows a future patch to remove KVM's
manual IA32_FEAT_CTL MSR checks.

Various features (on platforms that support IA32_FEAT_CTL) are dependent
on IA32_FEAT_CTL being configured and locked, e.g. VMX and LMCE.  The
MSR is always configured during boot, but only if the CPU vendor is
recognized by the kernel.  Because CPUID doesn't incorporate the current
IA32_FEAT_CTL value in its reporting of relevant features, it's possible
for a feature to be reported as supported in cpufeatures but not truly
enabled, e.g. if the CPU supports VMX but the kernel doesn't recognize
the CPU.

As a result, without the flag, KVM would see VMX as supported even if
IA32_FEAT_CTL hasn't been initialized, and so would need to manually
read the MSR and check the various enabling bits to avoid taking an
unexpected #GP on VMXON.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/kernel/cpu/feat_ctl.c     | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index e9b62498fe75..67d21b25ff78 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -220,6 +220,7 @@
 #define X86_FEATURE_ZEN			( 7*32+28) /* "" CPU is AMD family 0x17 (Zen) */
 #define X86_FEATURE_L1TF_PTEINV		( 7*32+29) /* "" L1TF workaround PTE inversion */
 #define X86_FEATURE_IBRS_ENHANCED	( 7*32+30) /* Enhanced IBRS */
+#define X86_FEATURE_MSR_IA32_FEAT_CTL	( 7*32+31) /* "" MSR IA32_FEAT_CTL configured */
 
 /* Virtualization flags: Linux defined, word 8 */
 #define X86_FEATURE_TPR_SHADOW		( 8*32+ 0) /* Intel TPR Shadow */
diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
index fcbb35533cef..24a4fdc1ab51 100644
--- a/arch/x86/kernel/cpu/feat_ctl.c
+++ b/arch/x86/kernel/cpu/feat_ctl.c
@@ -126,6 +126,8 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 	wrmsrl(MSR_IA32_FEAT_CTL, msr);
 
 update_caps:
+	set_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
+
 	if (!cpu_has(c, X86_FEATURE_VMX))
 		return;
 
-- 
2.24.1


  parent reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-21  4:44 [PATCH v5 00/19] x86/cpu: Clean up handling of VMX features Sean Christopherson
2019-12-21  4:44 ` [PATCH v5 01/19] x86/msr-index: Clean up bit defines for IA32_FEATURE_CONTROL MSR Sean Christopherson
2019-12-21  4:44 ` [PATCH v5 02/19] selftests: kvm: Replace manual MSR defs with common msr-index.h Sean Christopherson
2019-12-21  4:44 ` [PATCH v5 03/19] tools arch x86: Sync msr-index.h from kernel sources Sean Christopherson
2019-12-21  4:44 ` [PATCH v5 04/19] x86/intel: Initialize IA32_FEAT_CTL MSR at boot Sean Christopherson
2019-12-21  4:44 ` [PATCH v5 05/19] x86/mce: WARN once if IA32_FEAT_CTL MSR is left unlocked Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 06/19] x86/centaur: Use common IA32_FEAT_CTL MSR initialization Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 07/19] x86/zhaoxin: " Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 08/19] x86/cpu: Clear VMX feature flag if VMX is not fully enabled Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 09/19] x86/vmx: Introduce VMX_FEATURES_* Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 10/19] x86/cpu: Detect VMX features on Intel, Centaur and Zhaoxin CPUs Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 11/19] x86/cpu: Print VMX flags in /proc/cpuinfo using VMX_FEATURES_* Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 12/19] x86/cpu: Set synthetic VMX cpufeatures during init_ia32_feat_ctl() Sean Christopherson
2019-12-21  4:45 ` Sean Christopherson [this message]
2019-12-21  4:45 ` [PATCH v5 14/19] KVM: VMX: Drop initialization of IA32_FEAT_CTL MSR Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 15/19] KVM: VMX: Use VMX feature flag to query BIOS enabling Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 16/19] KVM: VMX: Check for full VMX support when verifying CPU compatibility Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 17/19] KVM: VMX: Use VMX_FEATURE_* flags to define VMCS control bits Sean Christopherson
2020-01-13 18:32   ` Borislav Petkov
2020-01-13 18:37     ` Sean Christopherson
2020-01-13 18:38       ` Borislav Petkov
2020-01-13 18:42         ` Sean Christopherson
2020-01-13 18:52           ` [PATCH] KVM: VMX: Rename define to CPU_BASED_USE_TSC_OFFSETTING Borislav Petkov
2020-01-13 20:16             ` Sean Christopherson
2020-01-14  9:31               ` Borislav Petkov
2020-01-14 17:27                 ` Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 18/19] perf/x86: Provide stubs of KVM helpers for non-Intel CPUs Sean Christopherson
2019-12-21  4:45 ` [PATCH v5 19/19] KVM: VMX: Allow KVM_INTEL when building for Centaur and/or Zhaoxin CPUs Sean Christopherson

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