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

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>

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 378ed944b849fb0448a13bd7f12a7a542ab7e388..3942b74c1b753c9f251807df276f709926bd8860 100644 (file)
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -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)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bdda3edddec93b2d2a932226059c1b7344722908..198d30cceaf2b1a23b5ea9dd20fa9e36a775720a 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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);

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index fe4ac03aaa3a81b062d59335a9e02c341f0bf567..b9096bb79c0096a9138f049dfe2695a950a409a6 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -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,

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1a3a4a92dc60f0a6df09a637040279b179a48183..c9e117506d737ac7a12e929136503f38f9743bc3 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -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;

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index e3b0985bb74a1f4d57be41cbb0d283abbc476625..65786dbe7d60bdf753db779312bb70754ccc6f1e 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -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;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e92f14b9d0d657f0957250ac9eefec38e095e74d..d9724a35d8f322ce5579d7228cbfcff71b073f96 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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))