[PATCH v3 2/2] KVM: X86: Ultra fast single target IPI fastpath
From: Sean Christopherson
Date: Fri Apr 10 2020 - 13:47:12 EST
From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
IPI and Timer cause the main MSRs write vmexits in cloud environment
observation, let's optimize virtual IPI latency more aggressively to
inject target IPI as soon as possible.
Running kvm-unit-tests/vmexit.flat IPI testing on SKX server, disable
adaptive advance lapic timer and adaptive halt-polling to avoid the
interference, this patch can give another 7% improvement.
w/o fastpath -> fastpath 4238 -> 3543 16.4%
fastpath -> ultra fastpath 3543 -> 3293 7%
w/o fastpath -> ultra fastpath 4238 -> 3293 22.3%
This also revises the performance data in commit 1e9e2622a1 (KVM: VMX:
FIXED+PHYSICAL mode single target IPI fastpath), that testing adds
--overcommit cpu-pm=on to kvm-unit-tests guest which is unnecessary.
Cc: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
Note, I dropped Haiwei Li's tested tag.
arch/x86/include/asm/kvm_host.h | 5 ++---
arch/x86/kvm/svm/svm.c | 24 ++++++++++++++++--------
arch/x86/kvm/vmx/vmx.c | 22 +++++++++++++---------
arch/x86/kvm/x86.c | 6 +++---
4 files changed, 34 insertions(+), 23 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c7da23aed79a..40cb197b4903 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1124,7 +1124,7 @@ struct kvm_x86_ops {
*/
void (*tlb_flush_guest)(struct kvm_vcpu *vcpu);
- void (*run)(struct kvm_vcpu *vcpu);
+ enum exit_fastpath_completion (*run)(struct kvm_vcpu *vcpu);
int (*handle_exit)(struct kvm_vcpu *vcpu,
enum exit_fastpath_completion exit_fastpath);
int (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);
@@ -1174,8 +1174,7 @@ struct kvm_x86_ops {
struct x86_instruction_info *info,
enum x86_intercept_stage stage,
struct x86_exception *exception);
- void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu,
- enum exit_fastpath_completion *exit_fastpath);
+ void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu);
int (*check_nested_events)(struct kvm_vcpu *vcpu);
void (*request_immediate_exit)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 27f4684a4c20..f40aa5a4253e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3283,10 +3283,21 @@ static void svm_cancel_injection(struct kvm_vcpu *vcpu)
svm_complete_interrupts(svm);
}
+static enum exit_fastpath_completion svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
+{
+ if (!is_guest_mode(vcpu) &&
+ to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR &&
+ to_svm(vcpu)->vmcb->control.exit_info_1)
+ return handle_fastpath_set_msr_irqoff(vcpu);
+
+ return EXIT_FASTPATH_NONE;
+}
+
bool __svm_vcpu_run(unsigned long vmcb_pa, unsigned long *regs);
-static void svm_vcpu_run(struct kvm_vcpu *vcpu)
+static enum exit_fastpath_completion svm_vcpu_run(struct kvm_vcpu *vcpu)
{
+ enum exit_fastpath_completion exit_fastpath;
struct vcpu_svm *svm = to_svm(vcpu);
svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];
@@ -3298,7 +3309,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
* again.
*/
if (unlikely(svm->nested.exit_required))
- return;
+ return EXIT_FASTPATH_NONE;
/*
* Disable singlestep if we're injecting an interrupt/exception.
@@ -3389,6 +3400,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
stgi();
/* Any pending NMI will happen here */
+ exit_fastpath = svm_exit_handlers_fastpath(vcpu);
if (unlikely(svm->vmcb->control.exit_code == SVM_EXIT_NMI))
kvm_after_interrupt(&svm->vcpu);
@@ -3417,6 +3429,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
svm_handle_mce(svm);
mark_all_clean(svm->vmcb);
+ return exit_fastpath;
}
STACK_FRAME_NON_STANDARD(svm_vcpu_run);
@@ -3719,13 +3732,8 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
return ret;
}
-static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu,
- enum exit_fastpath_completion *exit_fastpath)
+static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu)
{
- if (!is_guest_mode(vcpu) &&
- to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR &&
- to_svm(vcpu)->vmcb->control.exit_info_1)
- *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu);
}
static void svm_sched_in(struct kvm_vcpu *vcpu, int cpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index a8402bed29e3..a2e6c93a563b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6354,8 +6354,7 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
}
STACK_FRAME_NON_STANDARD(handle_external_interrupt_irqoff);
-static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu,
- enum exit_fastpath_completion *exit_fastpath)
+static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -6363,9 +6362,6 @@ static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu,
handle_external_interrupt_irqoff(vcpu);
else if (vmx->exit_reason == EXIT_REASON_EXCEPTION_NMI)
handle_exception_nmi_irqoff(vmx);
- else if (!is_guest_mode(vcpu) &&
- vmx->exit_reason == EXIT_REASON_MSR_WRITE)
- *exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu);
}
static bool vmx_has_emulated_msr(int index)
@@ -6572,8 +6568,9 @@ void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
-static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
+static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
+ enum exit_fastpath_completion exit_fastpath;
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long cr3, cr4;
@@ -6585,7 +6582,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
/* Don't enter VMX if guest state is invalid, let the exit handler
start emulation until we arrive back to a valid state */
if (vmx->emulation_required)
- return;
+ return EXIT_FASTPATH_NONE;
if (vmx->ple_window_dirty) {
vmx->ple_window_dirty = false;
@@ -6738,7 +6735,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (unlikely(vmx->fail)) {
vmx->exit_reason = 0xdead;
- return;
+ return EXIT_FASTPATH_NONE;
}
vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);
@@ -6746,13 +6743,20 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
kvm_machine_check();
if (unlikely(vmx->exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
- return;
+ return EXIT_FASTPATH_NONE;
+
+ if (!is_guest_mode(vcpu) && vmx->exit_reason == EXIT_REASON_MSR_WRITE)
+ exit_fastpath = handle_fastpath_set_msr_irqoff(vcpu);
+ else
+ exit_fastpath = EXIT_FASTPATH_NONE;
vmx->loaded_vmcs->launched = 1;
vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
vmx_recover_nmi_blocking(vmx);
vmx_complete_interrupts(vmx);
+
+ return exit_fastpath;
}
static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3089aa4ffedf..1c1af0d31267 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8182,7 +8182,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
bool req_int_win =
dm_request_for_irq_injection(vcpu) &&
kvm_cpu_accept_dm_intr(vcpu);
- enum exit_fastpath_completion exit_fastpath = EXIT_FASTPATH_NONE;
+ enum exit_fastpath_completion exit_fastpath;
bool req_immediate_exit = false;
@@ -8409,7 +8409,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD;
}
- kvm_x86_ops.run(vcpu);
+ exit_fastpath = kvm_x86_ops.run(vcpu);
/*
* Do this here before restoring debug registers on the host. And
@@ -8441,7 +8441,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
vcpu->mode = OUTSIDE_GUEST_MODE;
smp_wmb();
- kvm_x86_ops.handle_exit_irqoff(vcpu, &exit_fastpath);
+ kvm_x86_ops.handle_exit_irqoff(vcpu);
/*
* Consume any pending interrupts, including the possible source of
--
2.26.0