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Message-ID: <20250815001205.2370711-15-seanjc@google.com>
Date: Thu, 14 Aug 2025 17:11:58 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: stable@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Sasha Levin <sashal@...nel.org>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 6.1.y 14/21] KVM: x86: Fully defer to vendor code to decide
how to force immediate exit
[ Upstream commit 0ec3d6d1f169baa7fc512ae4b78d17e7c94b7763 ]
Now that vmx->req_immediate_exit is used only in the scope of
vmx_vcpu_run(), use force_immediate_exit to detect that KVM should usurp
the VMX preemption to force a VM-Exit and let vendor code fully handle
forcing a VM-Exit.
Opportunsitically drop __kvm_request_immediate_exit() and just have
vendor code call smp_send_reschedule() directly. SVM already does this
when injecting an event while also trying to single-step an IRET, i.e.
it's not exactly secret knowledge that KVM uses a reschedule IPI to force
an exit.
Link: https://lore.kernel.org/r/20240110012705.506918-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
[sean: resolve absurd conflict due to funky kvm_x86_ops.sched_in prototype]
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/include/asm/kvm-x86-ops.h | 1 -
arch/x86/include/asm/kvm_host.h | 3 ---
arch/x86/kvm/svm/svm.c | 7 ++++---
arch/x86/kvm/vmx/vmx.c | 32 +++++++++++++-----------------
arch/x86/kvm/vmx/vmx.h | 2 --
arch/x86/kvm/x86.c | 10 +---------
6 files changed, 19 insertions(+), 36 deletions(-)
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 29bef25ac77c..0e5ae3b0c867 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -100,7 +100,6 @@ KVM_X86_OP(write_tsc_multiplier)
KVM_X86_OP(get_exit_info)
KVM_X86_OP(check_intercept)
KVM_X86_OP(handle_exit_irqoff)
-KVM_X86_OP(request_immediate_exit)
KVM_X86_OP(sched_in)
KVM_X86_OP_OPTIONAL(update_cpu_dirty_logging)
KVM_X86_OP_OPTIONAL(vcpu_blocking)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 93f523762854..86f3bd6601e7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1590,8 +1590,6 @@ struct kvm_x86_ops {
struct x86_exception *exception);
void (*handle_exit_irqoff)(struct kvm_vcpu *vcpu);
- void (*request_immediate_exit)(struct kvm_vcpu *vcpu);
-
void (*sched_in)(struct kvm_vcpu *kvm, int cpu);
/*
@@ -2059,7 +2057,6 @@ extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
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);
void __user *__x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
u32 size);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 337a304d211b..12de50db401f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4033,8 +4033,11 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu,
* is enough to force an immediate vmexit.
*/
disable_nmi_singlestep(svm);
+ force_immediate_exit = true;
+ }
+
+ if (force_immediate_exit)
smp_send_reschedule(vcpu->cpu);
- }
pre_svm_run(vcpu);
@@ -4874,8 +4877,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.check_intercept = svm_check_intercept,
.handle_exit_irqoff = svm_handle_exit_irqoff,
- .request_immediate_exit = __kvm_request_immediate_exit,
-
.sched_in = svm_sched_in,
.nested_ops = &svm_nested_ops,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4db9d41d988c..179747d04edc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -49,6 +49,8 @@
#include <asm/virtext.h>
#include <asm/vmx.h>
+#include <trace/events/ipi.h>
+
#include "capabilities.h"
#include "cpuid.h"
#include "evmcs.h"
@@ -1223,8 +1225,6 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
u16 fs_sel, gs_sel;
int i;
- vmx->req_immediate_exit = false;
-
/*
* Note that guest MSRs to be saved/restored can also be changed
* when guest state is loaded. This happens when guest transitions
@@ -5929,7 +5929,8 @@ static int handle_pml_full(struct kvm_vcpu *vcpu)
return 1;
}
-static fastpath_t handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu)
+static fastpath_t handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu,
+ bool force_immediate_exit)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -5945,7 +5946,7 @@ static fastpath_t handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu)
* If the timer expired because KVM used it to force an immediate exit,
* then mission accomplished.
*/
- if (vmx->req_immediate_exit)
+ if (force_immediate_exit)
return EXIT_FASTPATH_EXIT_HANDLED;
/*
@@ -7090,13 +7091,13 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx)
msrs[i].host, false);
}
-static void vmx_update_hv_timer(struct kvm_vcpu *vcpu)
+static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
u64 tscl;
u32 delta_tsc;
- if (vmx->req_immediate_exit) {
+ if (force_immediate_exit) {
vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, 0);
vmx->loaded_vmcs->hv_timer_soft_disabled = false;
} else if (vmx->hv_deadline_tsc != -1) {
@@ -7149,7 +7150,8 @@ void noinstr vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx,
barrier_nospec();
}
-static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
+static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu,
+ bool force_immediate_exit)
{
/*
* If L2 is active, some VMX preemption timer exits can be handled in
@@ -7163,7 +7165,7 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
case EXIT_REASON_MSR_WRITE:
return handle_fastpath_set_msr_irqoff(vcpu);
case EXIT_REASON_PREEMPTION_TIMER:
- return handle_fastpath_preemption_timer(vcpu);
+ return handle_fastpath_preemption_timer(vcpu, force_immediate_exit);
default:
return EXIT_FASTPATH_NONE;
}
@@ -7284,7 +7286,9 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
vmx_passthrough_lbr_msrs(vcpu);
if (enable_preemption_timer)
- vmx_update_hv_timer(vcpu);
+ vmx_update_hv_timer(vcpu, force_immediate_exit);
+ else if (force_immediate_exit)
+ smp_send_reschedule(vcpu->cpu);
kvm_wait_lapic_expire(vcpu);
@@ -7358,7 +7362,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
vmx_recover_nmi_blocking(vmx);
vmx_complete_interrupts(vmx);
- return vmx_exit_handlers_fastpath(vcpu);
+ return vmx_exit_handlers_fastpath(vcpu, force_immediate_exit);
}
static void vmx_vcpu_free(struct kvm_vcpu *vcpu)
@@ -7865,11 +7869,6 @@ static __init void vmx_set_cpu_caps(void)
kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG);
}
-static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
-{
- to_vmx(vcpu)->req_immediate_exit = true;
-}
-
static int vmx_check_intercept_io(struct kvm_vcpu *vcpu,
struct x86_instruction_info *info)
{
@@ -8275,8 +8274,6 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
.check_intercept = vmx_check_intercept,
.handle_exit_irqoff = vmx_handle_exit_irqoff,
- .request_immediate_exit = vmx_request_immediate_exit,
-
.sched_in = vmx_sched_in,
.cpu_dirty_log_size = PML_ENTITY_NUM,
@@ -8533,7 +8530,6 @@ static __init int hardware_setup(void)
if (!enable_preemption_timer) {
vmx_x86_ops.set_hv_timer = NULL;
vmx_x86_ops.cancel_hv_timer = NULL;
- vmx_x86_ops.request_immediate_exit = __kvm_request_immediate_exit;
}
kvm_caps.supported_mce_cap |= MCG_LMCE_P;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 357819872d80..ddbe73958d7f 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -343,8 +343,6 @@ struct vcpu_vmx {
unsigned int ple_window;
bool ple_window_dirty;
- bool req_immediate_exit;
-
/* Support for PML */
#define PML_ENTITY_NUM 512
struct page *pml_pg;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 652f90ad7107..bc586a6df6ab 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10578,12 +10578,6 @@ static void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
static_call_cond(kvm_x86_set_apic_access_page_addr)(vcpu);
}
-void __kvm_request_immediate_exit(struct kvm_vcpu *vcpu)
-{
- smp_send_reschedule(vcpu->cpu);
-}
-EXPORT_SYMBOL_GPL(__kvm_request_immediate_exit);
-
/*
* Called within kvm->srcu read side.
* Returns 1 to let vcpu_run() continue the guest execution loop without
@@ -10817,10 +10811,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
goto cancel_injection;
}
- if (req_immediate_exit) {
+ if (req_immediate_exit)
kvm_make_request(KVM_REQ_EVENT, vcpu);
- static_call(kvm_x86_request_immediate_exit)(vcpu);
- }
fpregs_assert_state_consistent();
if (test_thread_flag(TIF_NEED_FPU_LOAD))
--
2.51.0.rc1.163.g2494970778-goog
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