[PATCH 6.12 263/460] KVM: x86: Introduce supported_quirks to block disabling quirks

Greg Kroah-Hartman
2026-03-23T14:42:22Z

6.12-stable review patch. If anyone has any objections, please let me know.

------------------

From: Yan Zhao <yan.y.zhao@intel.com>

[ Upstream commit bd7d5362b4c4ac8b951385867a0fadfae0ba3c07 ]

Introduce supported_quirks in kvm_caps to store platform-specific force-enabled
quirks.

No functional changes intended.

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Message-ID: <20250224070832.31394-1-yan.y.zhao@intel.com>
[Remove unsupported quirks at KVM_ENABLE_CAP time. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Stable-dep-of: e2ffe85b6d2b ("KVM: x86: Introduce KVM_X86_QUIRK_VMCS12_ALLOW_FREEZE_IN_SMM")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 9 +++++----
arch/x86/kvm/x86.h | 2 ++
2 files changed, 7 insertions(+), 4 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4801,7 +4801,7 @@ int kvm_vm_ioctl_check_extension(struct
r = enable_pmu ? KVM_CAP_PMU_VALID_MASK : 0;
break;
case KVM_CAP_DISABLE_QUIRKS2:
- r = KVM_X86_VALID_QUIRKS;
+ r = kvm_caps.supported_quirks;
break;
case KVM_CAP_X86_NOTIFY_VMEXIT:
r = kvm_caps.has_notify_vmexit;
@@ -6534,11 +6534,11 @@ int kvm_vm_ioctl_enable_cap(struct kvm *
switch (cap->cap) {
case KVM_CAP_DISABLE_QUIRKS2:
r = -EINVAL;
- if (cap->args[0] & ~KVM_X86_VALID_QUIRKS)
+ if (cap->args[0] & ~kvm_caps.supported_quirks)
break;
fallthrough;
case KVM_CAP_DISABLE_QUIRKS:
- kvm->arch.disabled_quirks |= cap->args[0];
+ kvm->arch.disabled_quirks |= cap->args[0] & kvm_caps.supported_quirks;
r = 0;
break;
case KVM_CAP_SPLIT_IRQCHIP: {
@@ -9782,6 +9782,7 @@ int kvm_x86_vendor_init(struct kvm_x86_i
kvm_host.xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
kvm_caps.supported_xcr0 = kvm_host.xcr0 & KVM_SUPPORTED_XCR0;
}
+ kvm_caps.supported_quirks = KVM_X86_VALID_QUIRKS;
kvm_caps.inapplicable_quirks = KVM_X86_CONDITIONAL_QUIRKS;

rdmsrl_safe(MSR_EFER, &kvm_host.efer);
@@ -12781,7 +12782,7 @@ int kvm_arch_init_vm(struct kvm *kvm, un
/* Decided by the vendor code for other VM types. */
kvm->arch.pre_fault_allowed =
type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM;
- kvm->arch.disabled_quirks = kvm_caps.inapplicable_quirks;
+ kvm->arch.disabled_quirks = kvm_caps.inapplicable_quirks & kvm_caps.supported_quirks;

ret = kvm_page_track_init(kvm);
if (ret)
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -32,6 +32,8 @@ struct kvm_caps {
u64 supported_xcr0;
u64 supported_xss;
u64 supported_perf_cap;
+
+ u64 supported_quirks;
u64 inapplicable_quirks;
};