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Date: Tue, 11 Jan 2022 15:35:39 +0000
From: Mark Rutland <mark.rutland@....com>
To: linux-kernel@...r.kernel.org
Cc: aleksandar.qemu.devel@...il.com, alexandru.elisei@....com,
anup.patel@....com, aou@...s.berkeley.edu, atish.patra@....com,
benh@...nel.crashing.org, borntraeger@...ux.ibm.com, bp@...en8.de,
catalin.marinas@....com, chenhuacai@...nel.org,
dave.hansen@...ux.intel.com, david@...hat.com,
frankja@...ux.ibm.com, frederic@...nel.org, gor@...ux.ibm.com,
hca@...ux.ibm.com, imbrenda@...ux.ibm.com, james.morse@....com,
jmattson@...gle.com, joro@...tes.org, kvm@...r.kernel.org,
mark.rutland@....com, maz@...nel.org, mingo@...hat.com,
mpe@...erman.id.au, nsaenzju@...hat.com, palmer@...belt.com,
paulmck@...nel.org, paulus@...ba.org, paul.walmsley@...ive.com,
pbonzini@...hat.com, seanjc@...gle.com, suzuki.poulose@....com,
tglx@...utronix.de, tsbogend@...ha.franken.de, vkuznets@...hat.com,
wanpengli@...cent.com, will@...nel.org
Subject: [PATCH 5/5] 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. This may result in a
small amount of additional time being acounted towards guests.
Other than this, there should be no functional change as a result of
this patch.
Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Jim Mattson <jmattson@...gle.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: Wanpeng Li <wanpengli@...cent.com>
---
arch/x86/kvm/svm/svm.c | 4 ++--
arch/x86/kvm/vmx/vmx.c | 4 ++--
arch/x86/kvm/x86.c | 4 +++-
arch/x86/kvm/x86.h | 45 ------------------------------------------
4 files changed, 7 insertions(+), 50 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 5151efa424ac..af5d90de243f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3814,7 +3814,7 @@ 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();
+ exit_to_guest_mode();
if (sev_es_guest(vcpu->kvm)) {
__svm_sev_es_vcpu_run(vmcb_pa);
@@ -3834,7 +3834,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
vmload(__sme_page_pa(sd->save_area));
}
- kvm_guest_exit_irqoff();
+ enter_from_guest_mode();
}
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 0dbf94eb954f..3dd240ef6414 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6593,7 +6593,7 @@ 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();
+ exit_to_guest_mode();
/* L1D Flush includes CPU buffer clear to mitigate MDS */
if (static_branch_unlikely(&vmx_l1d_should_flush))
@@ -6609,7 +6609,7 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
vcpu->arch.cr2 = native_read_cr2();
- kvm_guest_exit_irqoff();
+ enter_from_guest_mode();
}
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 e50e97ac4408..bd3873b90889 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9876,6 +9876,8 @@ 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
@@ -9949,7 +9951,7 @@ 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 4abcd8d9836d..8e50645ac740 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); \
--
2.30.2
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