[PATCH v3 10/16] KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable

Sean Christopherson
2021-09-22T00:06:43Z

Use the generic kvm_running_vcpu plus a new 'handling_intr_from_guest'
variable in kvm_arch_vcpu instead of the semi-redundant current_vcpu.
kvm_before/after_interrupt() must be called while the vCPU is loaded,
(which protects against preemption), thus kvm_running_vcpu is guaranteed
to be non-NULL when handling_intr_from_guest is non-zero.

Switching to kvm_get_running_vcpu() will allows moving KVM's perf
callbacks to generic code, and the new flag will be used in a future
patch to more precisely identify the "NMI from guest" case.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/kvm_host.h | 3 +--
arch/x86/kvm/pmu.c | 2 +-
arch/x86/kvm/x86.c | 21 ++++++++++++---------
arch/x86/kvm/x86.h | 10 ++++++----
4 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1080166fc0cf..2d86a2dfc775 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -763,6 +763,7 @@ struct kvm_vcpu_arch {
unsigned nmi_pending; /* NMI queued after currently running handler */
bool nmi_injected; /* Trying to inject an NMI this entry */
bool smi_pending; /* SMI queued after currently running handler */
+ u8 handling_intr_from_guest;

struct kvm_mtrr mtrr_state;
u64 pat;
@@ -1874,8 +1875,6 @@ int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu);
int kvm_complete_insn_gp(struct kvm_vcpu *vcpu, int err);
void __kvm_request_immediate_exit(struct kvm_vcpu *vcpu);

-unsigned int kvm_guest_state(void);
-
void __user *__x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
u32 size);
bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 5b68d4188de0..eef48258e50f 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -87,7 +87,7 @@ static void kvm_perf_overflow_intr(struct perf_event *perf_event,
* woken up. So we should wake it, but this is impossible from
* NMI context. Do it from irq work instead.
*/
- if (!kvm_guest_state())
+ if (!kvm_handling_nmi_from_guest(pmc->vcpu))
irq_work_queue(&pmc_to_pmu(pmc)->irq_work);
else
kvm_make_request(KVM_REQ_PMI, pmc->vcpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6cc66466f301..24a6faa07442 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8264,15 +8264,17 @@ static void kvm_timer_init(void)
kvmclock_cpu_online, kvmclock_cpu_down_prep);
}

-DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);
-EXPORT_PER_CPU_SYMBOL_GPL(current_vcpu);
+static inline bool kvm_pmi_in_guest(struct kvm_vcpu *vcpu)
+{
+ return vcpu && vcpu->arch.handling_intr_from_guest;
+}

-unsigned int kvm_guest_state(void)
+static unsigned int kvm_guest_state(void)
{
- struct kvm_vcpu *vcpu = __this_cpu_read(current_vcpu);
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
unsigned int state;

- if (!vcpu)
+ if (!kvm_pmi_in_guest(vcpu))
return 0;

state = PERF_GUEST_ACTIVE;
@@ -8284,9 +8286,10 @@ unsigned int kvm_guest_state(void)

static unsigned long kvm_guest_get_ip(void)
{
- struct kvm_vcpu *vcpu = __this_cpu_read(current_vcpu);
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();

- if (WARN_ON_ONCE(!vcpu))
+ /* Retrieving the IP must be guarded by a call to kvm_guest_state(). */
+ if (WARN_ON_ONCE(!kvm_pmi_in_guest(vcpu)))
return 0;

return kvm_rip_read(vcpu);
@@ -8294,10 +8297,10 @@ static unsigned long kvm_guest_get_ip(void)

static unsigned int kvm_handle_intel_pt_intr(void)
{
- struct kvm_vcpu *vcpu = __this_cpu_read(current_vcpu);
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();

/* '0' on failure so that the !PT case can use a RET0 static call. */
- if (!vcpu)
+ if (!kvm_pmi_in_guest(vcpu))
return 0;

kvm_make_request(KVM_REQ_PMI, vcpu);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 7d66d63dc55a..a9c107e7c907 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -387,18 +387,20 @@ static inline bool kvm_cstate_in_guest(struct kvm *kvm)
return kvm->arch.cstate_in_guest;
}

-DECLARE_PER_CPU(struct kvm_vcpu *, current_vcpu);
-
static inline void kvm_before_interrupt(struct kvm_vcpu *vcpu)
{
- __this_cpu_write(current_vcpu, vcpu);
+ WRITE_ONCE(vcpu->arch.handling_intr_from_guest, 1);
}

static inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
{
- __this_cpu_write(current_vcpu, NULL);
+ WRITE_ONCE(vcpu->arch.handling_intr_from_guest, 0);
}

+static inline bool kvm_handling_nmi_from_guest(struct kvm_vcpu *vcpu)
+{
+ return !!vcpu->arch.handling_intr_from_guest;
+}

static inline bool kvm_pat_valid(u64 data)
{
--
2.33.0.464.g1972c5931b-goog