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x86/entry: KVM: Use dedicated VMX NMI entry for 32-bit kernels too

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Use a dedicated entry for invoking the NMI handler from KVM VMX's VM-Exit
path for 32-bit even though using a dedicated entry for 32-bit isn't
strictly necessary.  Exposing a single symbol will allow KVM to reference
the entry point in assembly code without having to resort to more #ifdefs
(or #defines).  identry.h is intended to be included from asm files only
once, and so simply including idtentry.h in KVM assembly isn't an option.

Bypassing the ESP fixup and CR3 switching in the standard NMI entry code
is safe as KVM always handles NMIs that occur in the guest on a kernel
stack, with a kernel CR3.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221213060912.654668-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2022-12-13 06:09:10 +00:00
parent 432727f1cb
commit 54a3b70a75
3 changed files with 12 additions and 16 deletions
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16
arch/x86/include/asm/idtentry.h
View File

@ -582,18 +582,14 @@ DECLARE_IDTENTRY_RAW(X86_TRAP_MC, xenpv_exc_machine_check);
/* NMI */
#if defined(CONFIG_X86_64) && IS_ENABLED(CONFIG_KVM_INTEL)
#if IS_ENABLED(CONFIG_KVM_INTEL)
/*
* Special NOIST entry point for VMX which invokes this on the kernel
* stack. asm_exc_nmi() requires an IST to work correctly vs. the NMI
* 'executing' marker.
*
* On 32bit this just uses the regular NMI entry point because 32-bit does
* not have ISTs.
* Special entry point for VMX which invokes this on the kernel stack, even for
* 64-bit, i.e. without using an IST. asm_exc_nmi() requires an IST to work
* correctly vs. the NMI 'executing' marker. Used for 32-bit kernels as well
* to avoid more ifdeffery.
*/
DECLARE_IDTENTRY(X86_TRAP_NMI, exc_nmi_noist);
#else
#define asm_exc_nmi_noist asm_exc_nmi
DECLARE_IDTENTRY(X86_TRAP_NMI, exc_nmi_kvm_vmx);
#endif
DECLARE_IDTENTRY_NMI(X86_TRAP_NMI, exc_nmi);

8
arch/x86/kernel/nmi.c
View File

@ -527,14 +527,14 @@ nmi_restart:
mds_user_clear_cpu_buffers();
}
#if defined(CONFIG_X86_64) && IS_ENABLED(CONFIG_KVM_INTEL)
DEFINE_IDTENTRY_RAW(exc_nmi_noist)
#if IS_ENABLED(CONFIG_KVM_INTEL)
DEFINE_IDTENTRY_RAW(exc_nmi_kvm_vmx)
{
exc_nmi(regs);
}
#endif
#if IS_MODULE(CONFIG_KVM_INTEL)
EXPORT_SYMBOL_GPL(asm_exc_nmi_noist);
EXPORT_SYMBOL_GPL(asm_exc_nmi_kvm_vmx);
#endif
#endif
void stop_nmi(void)

4
arch/x86/kvm/vmx/vmx.c
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@ -6866,7 +6866,7 @@ void vmx_do_interrupt_nmi_irqoff(unsigned long entry);
static void handle_interrupt_nmi_irqoff(struct kvm_vcpu *vcpu,
unsigned long entry)
{
bool is_nmi = entry == (unsigned long)asm_exc_nmi_noist;
bool is_nmi = entry == (unsigned long)asm_exc_nmi_kvm_vmx;
kvm_before_interrupt(vcpu, is_nmi ? KVM_HANDLING_NMI : KVM_HANDLING_IRQ);
vmx_do_interrupt_nmi_irqoff(entry);
@ -6895,7 +6895,7 @@ static void handle_nm_fault_irqoff(struct kvm_vcpu *vcpu)
static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx)
{
const unsigned long nmi_entry = (unsigned long)asm_exc_nmi_noist;
const unsigned long nmi_entry = (unsigned long)asm_exc_nmi_kvm_vmx;
u32 intr_info = vmx_get_intr_info(&vmx->vcpu);
/* if exit due to PF check for async PF */