This is a note to let you know that I've just added the patch titled KVM: x86: Supplement __cr4_reserved_bits() with X86_FEATURE_PCID check to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-x86-supplement-__cr4_reserved_bits-with-x86_feat.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit f310fd979060aeb903615b6759a685ad113e9575 Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Date: Mon Feb 1 15:28:43 2021 +0100 KVM: x86: Supplement __cr4_reserved_bits() with X86_FEATURE_PCID check [ Upstream commit 4683d758f48e6ae87d3d3493ffa00aceb955ee16 ] Commit 7a873e455567 ("KVM: selftests: Verify supported CR4 bits can be set before KVM_SET_CPUID2") reveals that KVM allows to set X86_CR4_PCIDE even when PCID support is missing: ==== Test Assertion Failure ==== x86_64/set_sregs_test.c:41: rc pid=6956 tid=6956 - Invalid argument 1 0x000000000040177d: test_cr4_feature_bit at set_sregs_test.c:41 2 0x00000000004014fc: main at set_sregs_test.c:119 3 0x00007f2d9346d041: ?? ??:0 4 0x000000000040164d: _start at ??:? KVM allowed unsupported CR4 bit (0x20000) Add X86_FEATURE_PCID feature check to __cr4_reserved_bits() to make kvm_is_valid_cr4() fail. Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Message-Id: <20210201142843.108190-1-vkuznets@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index e7ca622a468f..2249a7d7ca27 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -404,6 +404,8 @@ bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type); __reserved_bits |= X86_CR4_UMIP; \ if (!__cpu_has(__c, X86_FEATURE_VMX)) \ __reserved_bits |= X86_CR4_VMXE; \ + if (!__cpu_has(__c, X86_FEATURE_PCID)) \ + __reserved_bits |= X86_CR4_PCIDE; \ __reserved_bits; \ })