From: Anil Altinay <aaltinay@google.com>
To: stable@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Anil Altinay <aaltinay@google.com>
Subject: [PATCH 6.18.y v2 2/6] KVM: x86: Consolidate CPUID fault handling for emulator and interception logic
Date: Thu, 15 Oct 2026 16:03:42 +0000 [thread overview]
Message-ID: <20261015160346.181835-3-aaltinay@google.com> (raw)
In-Reply-To: <20261015160346.181835-1-aaltinay@google.com>
From: Sean Christopherson <seanjc@google.com>
commit cf7d65d1d6f50daadfe7c475f0c2b1bfdc288b56 upstream.
Extract the logic for emulating CPUID faulting (where CPUID #GPs at CPL>0
outside of SMM) into a dedicated helper and use the helper for both the
full emulator and the intercepted-CPUID paths.
Opportunistically drop kvm_require_cpl(), as kvm_emulate_cpuid() was the
one and only user.
No functional change intended.
[jim: Add EXPORT_STATIC_CALL_GPL(kvm_x86_get_cpl) so that KVM vendor
modules can call kvm_is_cpuid_allowed(). Fix typo in commit message.]
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://patch.msgid.link/20260527174347.2356165-2-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
[ Resolve minor context conflict in arch/x86/include/asm/kvm_host.h ]
Signed-off-by: Anil Altinay <aaltinay@google.com>
---
arch/x86/include/asm/kvm_host.h | 1 -
arch/x86/kvm/cpuid.c | 5 +++--
arch/x86/kvm/cpuid.h | 8 ++++++++
arch/x86/kvm/emulate.c | 6 +-----
arch/x86/kvm/kvm_emulate.h | 1 +
arch/x86/kvm/x86.c | 19 +++++++------------
6 files changed, 20 insertions(+), 20 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b2cf3431e259..0458f51a571e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2255,7 +2255,6 @@ void kvm_requeue_exception(struct kvm_vcpu *vcpu, unsigned int nr,
void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);
void kvm_inject_emulated_page_fault(struct kvm_vcpu *vcpu,
struct x86_exception *fault);
-bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);
bool kvm_require_dr(struct kvm_vcpu *vcpu, int dr);
static inline int __kvm_irq_line_state(unsigned long *irq_state,
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index bfa89fbe826b..3f2689fdc304 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -2098,9 +2098,10 @@ int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
{
u32 eax, ebx, ecx, edx;
- if (!is_smm(vcpu) && cpuid_fault_enabled(vcpu) &&
- !kvm_require_cpl(vcpu, 0))
+ if (!kvm_is_cpuid_allowed(vcpu)) {
+ kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
return 1;
+ }
eax = kvm_rax_read(vcpu);
ecx = kvm_rcx_read(vcpu);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index d3f5ae15a7ca..c5399ab7e5ae 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -7,6 +7,8 @@
#include <asm/processor.h>
#include <uapi/asm/kvm_para.h>
+#include "smm.h"
+
extern u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
void kvm_set_cpu_caps(void);
@@ -184,6 +186,12 @@ static inline bool cpuid_fault_enabled(struct kvm_vcpu *vcpu)
MSR_MISC_FEATURES_ENABLES_CPUID_FAULT;
}
+static inline bool kvm_is_cpuid_allowed(struct kvm_vcpu *vcpu)
+{
+ return !cpuid_fault_enabled(vcpu) || is_smm(vcpu) ||
+ !kvm_x86_call(get_cpl)(vcpu);
+}
+
static __always_inline void kvm_cpu_cap_clear(unsigned int x86_feature)
{
unsigned int x86_leaf = __feature_leaf(x86_feature);
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8aa10d0e9894..54a1528003fa 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3557,12 +3557,8 @@ static int em_sti(struct x86_emulate_ctxt *ctxt)
static int em_cpuid(struct x86_emulate_ctxt *ctxt)
{
u32 eax, ebx, ecx, edx;
- u64 msr = 0;
- ctxt->ops->get_msr(ctxt, MSR_MISC_FEATURES_ENABLES, &msr);
- if (!ctxt->ops->is_smm(ctxt) &&
- (msr & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT) &&
- ctxt->ops->cpl(ctxt))
+ if (!ctxt->ops->is_cpuid_allowed(ctxt))
return emulate_gp(ctxt, 0);
eax = reg_read(ctxt, VCPU_REGS_RAX);
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 7b5ddb787a25..c0dcfebcec07 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -225,6 +225,7 @@ struct x86_emulate_ops {
struct x86_instruction_info *info,
enum x86_intercept_stage stage);
+ bool (*is_cpuid_allowed)(struct x86_emulate_ctxt *ctxt);
bool (*get_cpuid)(struct x86_emulate_ctxt *ctxt, u32 *eax, u32 *ebx,
u32 *ecx, u32 *edx, bool exact_only);
bool (*guest_has_movbe)(struct x86_emulate_ctxt *ctxt);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ae33393c9b47..6f76290e79c9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -138,6 +138,7 @@ struct kvm_x86_ops kvm_x86_ops __read_mostly;
#include <asm/kvm-x86-ops.h>
EXPORT_STATIC_CALL_GPL(kvm_x86_get_cs_db_l_bits);
EXPORT_STATIC_CALL_GPL(kvm_x86_cache_reg);
+EXPORT_STATIC_CALL_GPL(kvm_x86_get_cpl);
#define KVM_X86_NESTED_OP(func) \
DEFINE_STATIC_CALL_NULL(kvm_x86_nested_##func, \
@@ -1011,18 +1012,6 @@ void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_queue_exception_e);
-/*
- * Checks if cpl <= required_cpl; if true, return true. Otherwise queue
- * a #GP and return false.
- */
-bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl)
-{
- if (kvm_x86_call(get_cpl)(vcpu) <= required_cpl)
- return true;
- kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
- return false;
-}
-
bool kvm_require_dr(struct kvm_vcpu *vcpu, int dr)
{
if ((dr != 4 && dr != 5) || !kvm_is_cr4_bit_set(vcpu, X86_CR4_DE))
@@ -8422,6 +8411,11 @@ static int emulator_intercept(struct x86_emulate_ctxt *ctxt,
&ctxt->exception);
}
+static bool emulator_is_cpuid_allowed(struct x86_emulate_ctxt *ctxt)
+{
+ return kvm_is_cpuid_allowed(emul_to_vcpu(ctxt));
+}
+
static bool emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
u32 *eax, u32 *ebx, u32 *ecx, u32 *edx,
bool exact_only)
@@ -8545,6 +8539,7 @@ static const struct x86_emulate_ops emulate_ops = {
.wbinvd = emulator_wbinvd,
.fix_hypercall = emulator_fix_hypercall,
.intercept = emulator_intercept,
+ .is_cpuid_allowed = emulator_is_cpuid_allowed,
.get_cpuid = emulator_get_cpuid,
.guest_has_movbe = emulator_guest_has_movbe,
.guest_has_fxsr = emulator_guest_has_fxsr,
--
2.56.0.385.gd3acb90ef8-goog
next prev parent reply other threads:[~2026-10-15 16:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 16:03 [PATCH 6.18.y v2 0/6] KVM: x86: CPUID faulting fixes and AMD CPUID faulting virtualization Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 1/6] KVM: x86: Ignore cpuid faulting in SMM Anil Altinay
2026-10-15 16:03 ` Anil Altinay [this message]
2026-10-15 16:03 ` [PATCH 6.18.y v2 3/6] KVM: x86: Prioritize CPUID faulting over CPUID VM-exits in nested VMX Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 4/6] KVM: x86: Remove supports_cpuid_fault() helper Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 5/6] KVM: x86: Virtualize AMD CPUID faulting Anil Altinay
2026-10-15 16:03 ` [PATCH 6.18.y v2 6/6] KVM: selftests: Update hwcr_msr_test for CPUID faulting bit Anil Altinay
2026-10-16 1:09 ` [PATCH 6.18.y v2 0/6] KVM: x86: CPUID faulting fixes and AMD CPUID faulting virtualization Sean Christopherson
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