Merge tag 'kvm-x86-misc-6.9' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.9:

 - Explicitly initialize a variety of on-stack variables in the emulator that
   triggered KMSAN false positives (though in fairness in KMSAN, it's comically
   difficult to see that the uninitialized memory is never truly consumed).

 - Fix the deubgregs ABI for 32-bit KVM, and clean up code related to reading
   DR6 and DR7.

 - Rework the "force immediate exit" code so that vendor code ultimately
   decides how and when to force the exit.  This allows VMX to further optimize
   handling preemption timer exits, and allows SVM to avoid sending a duplicate
   IPI (SVM also has a need to force an exit).

 - Fix a long-standing bug where kvm_has_noapic_vcpu could be left elevated if
   vCPU creation ultimately failed, and add WARN to guard against similar bugs.

 - Provide a dedicated arch hook for checking if a different vCPU was in-kernel
   (for directed yield), and simplify the logic for checking if the currently
   loaded vCPU is in-kernel.

 - Misc cleanups and fixes.

3 files changed, 54 insertions, 35 deletions

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 6329a306856b..0cd977f22c4b 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4433,7 +4433,7 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 		(vm_entry_controls_get(to_vmx(vcpu)) & VM_ENTRY_IA32E_MODE);
 
 	if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_DEBUG_CONTROLS)
-		kvm_get_dr(vcpu, 7, (unsigned long *)&vmcs12->guest_dr7);
+		vmcs12->guest_dr7 = vcpu->arch.dr7;
 
 	if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_IA32_EFER)
 		vmcs12->guest_ia32_efer = vcpu->arch.efer;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 88a4ff200d04..fa3c3abb50e4 100644
--- 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"
@@ -1290,8 +1292,6 @@ 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
@@ -5575,10 +5575,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 
 	reg = DEBUG_REG_ACCESS_REG(exit_qualification);
 	if (exit_qualification & TYPE_MOV_FROM_DR) {
-		unsigned long val;
-
-		kvm_get_dr(vcpu, dr, &val);
-		kvm_register_write(vcpu, reg, val);
+		kvm_register_write(vcpu, reg, kvm_get_dr(vcpu, dr));
 		err = 0;
 	} else {
 		err = kvm_set_dr(vcpu, dr, kvm_register_read(vcpu, reg));
@@ -6000,22 +5997,46 @@ 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);
 
-	if (!vmx->req_immediate_exit &&
-	    !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) {
-		kvm_lapic_expired_hv_timer(vcpu);
+	/*
+	 * In the *extremely* unlikely scenario that this is a spurious VM-Exit
+	 * due to the timer expiring while it was "soft" disabled, just eat the
+	 * exit and re-enter the guest.
+	 */
+	if (unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled))
 		return EXIT_FASTPATH_REENTER_GUEST;
-	}
 
-	return EXIT_FASTPATH_NONE;
+	/*
+	 * If the timer expired because KVM used it to force an immediate exit,
+	 * then mission accomplished.
+	 */
+	if (force_immediate_exit)
+		return EXIT_FASTPATH_EXIT_HANDLED;
+
+	/*
+	 * If L2 is active, go down the slow path as emulating the guest timer
+	 * expiration likely requires synthesizing a nested VM-Exit.
+	 */
+	if (is_guest_mode(vcpu))
+		return EXIT_FASTPATH_NONE;
+
+	kvm_lapic_expired_hv_timer(vcpu);
+	return EXIT_FASTPATH_REENTER_GUEST;
 }
 
 static int handle_preemption_timer(struct kvm_vcpu *vcpu)
 {
-	handle_fastpath_preemption_timer(vcpu);
+	/*
+	 * This non-fastpath handler is reached if and only if the preemption
+	 * timer was being used to emulate a guest timer while L2 is active.
+	 * All other scenarios are supposed to be handled in the fastpath.
+	 */
+	WARN_ON_ONCE(!is_guest_mode(vcpu));
+	kvm_lapic_expired_hv_timer(vcpu);
 	return 1;
 }
 
@@ -7155,13 +7176,13 @@ 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) {
@@ -7214,13 +7235,22 @@ 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
+	 * the fastpath even, all other exits must use the slow path.
+	 */
+	if (is_guest_mode(vcpu) &&
+	    to_vmx(vcpu)->exit_reason.basic != EXIT_REASON_PREEMPTION_TIMER)
+		return EXIT_FASTPATH_NONE;
+
 	switch (to_vmx(vcpu)->exit_reason.basic) {
 	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;
 	}
@@ -7280,7 +7310,7 @@ out:
 	guest_state_exit_irqoff();
 }
 
-static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
+static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	unsigned long cr3, cr4;
@@ -7307,7 +7337,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		return EXIT_FASTPATH_NONE;
 	}
 
-	trace_kvm_entry(vcpu);
+	trace_kvm_entry(vcpu, force_immediate_exit);
 
 	if (vmx->ple_window_dirty) {
 		vmx->ple_window_dirty = false;
@@ -7366,7 +7396,9 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		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);
 
@@ -7430,10 +7462,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
 	vmx_recover_nmi_blocking(vmx);
 	vmx_complete_interrupts(vmx);
 
-	if (is_guest_mode(vcpu))
-		return EXIT_FASTPATH_NONE;
-
-	return vmx_exit_handlers_fastpath(vcpu);
+	return vmx_exit_handlers_fastpath(vcpu, force_immediate_exit);
 }
 
 static void vmx_vcpu_free(struct kvm_vcpu *vcpu)
@@ -7913,11 +7942,6 @@ 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)
 {
@@ -8370,8 +8394,6 @@ 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,
@@ -8631,7 +8653,6 @@ 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 e3b0985bb74a..65786dbe7d60 100644
--- 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;