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KVM: x86: Fully defer to vendor code to decide how to force immediate exit

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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@google.com>
This commit is contained in:
Sean Christopherson 2024-01-09 17:27:05 -08:00
parent 7b3d1bbf8d
commit 0ec3d6d1f1
6 changed files with 19 additions and 36 deletions
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1
arch/x86/include/asm/kvm-x86-ops.h
View file

@ -103,7 +103,6 @@ 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)

3
arch/x86/include/asm/kvm_host.h
View file

@ -1732,8 +1732,6 @@ 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 *vcpu, int cpu);
/*
@ -2239,7 +2237,6 @@ 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);

7
arch/x86/kvm/svm/svm.c
View file

@ -4140,9 +4140,12 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu,
* is enough to force an immediate vmexit.
*/
disable_nmi_singlestep(svm);
smp_send_reschedule(vcpu->cpu);
force_immediate_exit = true;
}
if (force_immediate_exit)
smp_send_reschedule(vcpu->cpu);
pre_svm_run(vcpu);
sync_lapic_to_cr8(vcpu);
@ -4995,8 +4998,6 @@ 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,

32
arch/x86/kvm/vmx/vmx.c
View file

@ -49,6 +49,8 @@
#include <asm/spec-ctrl.h>
#include <asm/vmx.h>
#include <trace/events/ipi.h>
#include "capabilities.h"
#include "cpuid.h"
#include "hyperv.h"
@ -1281,8 +1283,6 @@ 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
@ -5988,7 +5988,8 @@ 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);
@ -6004,7 +6005,7 @@ 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;
/*
@ -7166,13 +7167,13 @@ 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) {
@ -7225,7 +7226,8 @@ 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
@ -7239,7 +7241,7 @@ 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;
}
@ -7382,7 +7384,9 @@ 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);
@ -7446,7 +7450,7 @@ 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)
@ -7926,11 +7930,6 @@ 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)
{
@ -8383,8 +8382,6 @@ 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,
@ -8644,7 +8641,6 @@ 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;

2
arch/x86/kvm/vmx/vmx.h
View file

@ -332,8 +332,6 @@ 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;

10
arch/x86/kvm/x86.c
View file

@ -10667,12 +10667,6 @@ 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
@ -10922,10 +10916,8 @@ 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))