diff options
| author | Sean Christopherson <seanjc@google.com> | 2023-04-14 02:19:14 +0300 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-05-26 23:50:42 +0300 |
| commit | 023cfa6fc200fc179dbf8e1857cc7140fa1466f9 (patch) | |
| tree | 9aeda27d691ceca8324877e259185ffc35455150 /arch/x86/kvm/vmx | |
| parent | 3243b93c16d90c2d63cf30655276ffdf5bb65bf7 (diff) | |
| download | linux-023cfa6fc200fc179dbf8e1857cc7140fa1466f9.tar.xz | |
KVM: VMX: Use proper accessor to read guest CR4 in handle_desc()
Use kvm_is_cr4_bit_set() to read guest CR4.UMIP when sanity checking that
a descriptor table VM-Exit occurs if and only if guest.CR4.UMIP=1. UMIP
can't be guest-owned, i.e. using kvm_read_cr4_bits() to decache guest-
owned bits isn't strictly necessary, but eliminating raw reads of
vcpu->arch.cr4 is desirable as it makes it easy to visually audit KVM for
correctness.
Opportunistically add a compile-time assertion that UMIP isn't guest-owned
as letting the guest own UMIP isn't compatible with emulation (or any CR4
bit that is emulated by KVM).
Opportunistically change the WARN_ON() to a ONCE variant. When the WARN
fires, it fires _a lot_, and spamming the kernel logs ends up doing more
harm than whatever led to KVM's unnecessary emulation.
Reported-by: Robert Hoo <robert.hu@intel.com>
Link: https://lore.kernel.org/all/20230310125718.1442088-4-robert.hu@intel.com
Link: https://lore.kernel.org/r/20230413231914.1482782-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/vmx')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 98f966635c88..7ecab2118106 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5402,7 +5402,13 @@ static int handle_set_cr4(struct kvm_vcpu *vcpu, unsigned long val) static int handle_desc(struct kvm_vcpu *vcpu) { - WARN_ON(!(vcpu->arch.cr4 & X86_CR4_UMIP)); + /* + * UMIP emulation relies on intercepting writes to CR4.UMIP, i.e. this + * and other code needs to be updated if UMIP can be guest owned. + */ + BUILD_BUG_ON(KVM_POSSIBLE_CR4_GUEST_BITS & X86_CR4_UMIP); + + WARN_ON_ONCE(!kvm_is_cr4_bit_set(vcpu, X86_CR4_UMIP)); return kvm_emulate_instruction(vcpu, 0); } |