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KVM: x86: Consolidate CPUID fault handling for emulator and interception logic

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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>
This commit is contained in:
Sean Christopherson 2026-05-27 10:43:43 -07:00
parent 986833d381
commit cf7d65d1d6
6 changed files with 20 additions and 20 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -2320,7 +2320,6 @@ static inline void kvm_inject_emulated_page_fault(struct kvm_vcpu *vcpu,
__kvm_inject_emulated_page_fault(vcpu, fault, false);
}
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,

5
arch/x86/kvm/cpuid.c
View File

@ -2161,9 +2161,10 @@ 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);

8
arch/x86/kvm/cpuid.h
View File

@ -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;
extern bool kvm_is_configuring_cpu_caps __read_mostly;
@ -192,6 +194,12 @@ 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);

6
arch/x86/kvm/emulate.c
View File

@ -3594,12 +3594,8 @@ 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);

1
arch/x86/kvm/kvm_emulate.h
View File

@ -230,6 +230,7 @@ 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);

19
arch/x86/kvm/x86.c
View File

@ -151,6 +151,7 @@ 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);
static bool __read_mostly ignore_msrs = 0;
module_param(ignore_msrs, bool, 0644);
@ -1022,18 +1023,6 @@ 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))
@ -8824,6 +8813,11 @@ 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)
@ -8961,6 +8955,7 @@ 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,