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authorMark Rutland <mark.rutland@arm.com>2022-02-01 13:29:24 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2022-02-01 08:51:54 -0500
commitb2d2af7e5df37ee3a9ba6b405bdbb7691a5c2dfc (patch)
treeda82014ced1994048dad46f6d30a6f192859b7b2 /arch
parent72e3244512b34756a7e8aa67eff45cdcb040ac4e (diff)
kvm/x86: rework guest entry logic
For consistency and clarity, migrate x86 over to the generic helpers for guest timing and lockdep/RCU/tracing management, and remove the x86-specific helpers. Prior to this patch, the guest timing was entered in kvm_guest_enter_irqoff() (called by svm_vcpu_enter_exit() and svm_vcpu_enter_exit()), and was exited by the call to vtime_account_guest_exit() within vcpu_enter_guest(). To minimize duplication and to more clearly balance entry and exit, both entry and exit of guest timing are placed in vcpu_enter_guest(), using the new guest_timing_{enter,exit}_irqoff() helpers. When context tracking is used a small amount of additional time will be accounted towards guests; tick-based accounting is unnaffected as IRQs are disabled at this point and not enabled until after the return from the guest. This also corrects (benign) mis-balanced context tracking accounting introduced in commits: ae95f566b3d22ade ("KVM: X86: TSCDEADLINE MSR emulation fastpath") 26efe2fd92e50822 ("KVM: VMX: Handle preemption timer fastpath") Where KVM can enter a guest multiple times, calling vtime_guest_enter() without a corresponding call to vtime_account_guest_exit(), and with vtime_account_system() called when vtime_account_guest() should be used. As account_system_time() checks PF_VCPU and calls account_guest_time(), this doesn't result in any functional problem, but is unnecessarily confusing. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jim Mattson <jmattson@google.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Sean Christopherson <seanjc@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Wanpeng Li <wanpengli@tencent.com> Message-Id: <20220201132926.3301912-4-mark.rutland@arm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/svm/svm.c4
-rw-r--r--arch/x86/kvm/vmx/vmx.c4
-rw-r--r--arch/x86/kvm/x86.c4
-rw-r--r--arch/x86/kvm/x86.h45
4 files changed, 7 insertions, 50 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 5772dd6f79a4..ea2f7f3614af 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3630,7 +3630,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
struct vcpu_svm *svm = to_svm(vcpu);
unsigned long vmcb_pa = svm->current_vmcb->pa;
- kvm_guest_enter_irqoff();
+ guest_state_enter_irqoff();
if (sev_es_guest(vcpu->kvm)) {
__svm_sev_es_vcpu_run(vmcb_pa);
@@ -3650,7 +3650,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
vmload(__sme_page_pa(sd->save_area));
}
- kvm_guest_exit_irqoff();
+ guest_state_exit_irqoff();
}
static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 3c0ba5b1bbcf..c0c256c33d21 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6767,7 +6767,7 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
struct vcpu_vmx *vmx)
{
- kvm_guest_enter_irqoff();
+ guest_state_enter_irqoff();
/* L1D Flush includes CPU buffer clear to mitigate MDS */
if (static_branch_unlikely(&vmx_l1d_should_flush))
@@ -6783,7 +6783,7 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
vcpu->arch.cr2 = native_read_cr2();
- kvm_guest_exit_irqoff();
+ guest_state_exit_irqoff();
}
static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c25a6ef0ff06..fec3dd4f0718 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10088,6 +10088,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
set_debugreg(0, 7);
}
+ guest_timing_enter_irqoff();
+
for (;;) {
/*
* Assert that vCPU vs. VM APICv state is consistent. An APICv
@@ -10172,7 +10174,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
* of accounting via context tracking, but the loss of accuracy is
* acceptable for all known use cases.
*/
- vtime_account_guest_exit();
+ guest_timing_exit_irqoff();
if (lapic_in_kernel(vcpu)) {
s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 1ebd5a7594da..20c7a1fb90bb 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -10,51 +10,6 @@
void kvm_spurious_fault(void);
-static __always_inline void kvm_guest_enter_irqoff(void)
-{
- /*
- * VMENTER enables interrupts (host state), but the kernel state is
- * interrupts disabled when this is invoked. Also tell RCU about
- * it. This is the same logic as for exit_to_user_mode().
- *
- * This ensures that e.g. latency analysis on the host observes
- * guest mode as interrupt enabled.
- *
- * guest_enter_irqoff() informs context tracking about the
- * transition to guest mode and if enabled adjusts RCU state
- * accordingly.
- */
- instrumentation_begin();
- trace_hardirqs_on_prepare();
- lockdep_hardirqs_on_prepare(CALLER_ADDR0);
- instrumentation_end();
-
- guest_enter_irqoff();
- lockdep_hardirqs_on(CALLER_ADDR0);
-}
-
-static __always_inline void kvm_guest_exit_irqoff(void)
-{
- /*
- * VMEXIT disables interrupts (host state), but tracing and lockdep
- * have them in state 'on' as recorded before entering guest mode.
- * Same as enter_from_user_mode().
- *
- * context_tracking_guest_exit() restores host context and reinstates
- * RCU if enabled and required.
- *
- * This needs to be done immediately after VM-Exit, before any code
- * that might contain tracepoints or call out to the greater world,
- * e.g. before x86_spec_ctrl_restore_host().
- */
- lockdep_hardirqs_off(CALLER_ADDR0);
- context_tracking_guest_exit();
-
- instrumentation_begin();
- trace_hardirqs_off_finish();
- instrumentation_end();
-}
-
#define KVM_NESTED_VMENTER_CONSISTENCY_CHECK(consistency_check) \
({ \
bool failed = (consistency_check); \