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KVM: x86: Make vmx_get_exit_qual() and vmx_get_intr_info() noinstr-friendly

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Add an extra special noinstr-friendly helper to test+mark a "register"
available and use it when caching vmcs.EXIT_QUALIFICATION and
vmcs.VM_EXIT_INTR_INFO.  Make the caching helpers __always_inline too so
that they can be used in noinstr functions.

A future fix will move VMX's handling of NMI exits into the noinstr
vmx_vcpu_enter_exit() so that the NMI is processed before any kind of
instrumentation can trigger a fault and thus IRET, i.e. so that KVM
doesn't invoke the NMI handler with NMIs enabled.

Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221213060912.654668-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2022-12-13 06:09:06 +00:00
parent e8733482f5
commit fc9465be8a
2 changed files with 18 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
arch/x86/kvm/kvm_cache_regs.h
View file

@ -75,6 +75,18 @@ static inline void kvm_register_mark_dirty(struct kvm_vcpu *vcpu,
__set_bit(reg, (unsigned long *)&vcpu->arch.regs_dirty);
}
/*
* kvm_register_test_and_mark_available() is a special snowflake that uses an
* arch bitop directly to avoid the explicit instrumentation that comes with
* the generic bitops. This allows code that cannot be instrumented (noinstr
* functions), e.g. the low level VM-Enter/VM-Exit paths, to cache registers.
*/
static __always_inline bool kvm_register_test_and_mark_available(struct kvm_vcpu *vcpu,
enum kvm_reg reg)
{
return arch___test_and_set_bit(reg, (unsigned long *)&vcpu->arch.regs_avail);
}
/*
* The "raw" register helpers are only for cases where the full 64 bits of a
* register are read/written irrespective of current vCPU mode. In other words,

14
arch/x86/kvm/vmx/vmx.h
View file

@ -669,25 +669,23 @@ void intel_pmu_cross_mapped_check(struct kvm_pmu *pmu);
int intel_pmu_create_guest_lbr_event(struct kvm_vcpu *vcpu);
void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu);
static inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
static __always_inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
if (!kvm_register_is_available(vcpu, VCPU_EXREG_EXIT_INFO_1)) {
kvm_register_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_1);
if (!kvm_register_test_and_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_1))
vmx->exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
}
return vmx->exit_qualification;
}
static inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
static __always_inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
if (!kvm_register_is_available(vcpu, VCPU_EXREG_EXIT_INFO_2)) {
kvm_register_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_2);
if (!kvm_register_test_and_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_2))
vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
}
return vmx->exit_intr_info;
}