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Subject[PATCH 03/28] KVM: nSVM: inject exceptions via svm_check_nested_events
Date
This allows exceptions injected by the emulator to be properly delivered
as vmexits. The code also becomes simpler, because we can just let all
L0-intercepted exceptions go through the usual path. In particular, our
emulation of the VMX #DB exit qualification is very much simplified,
because the vmexit injection path can use kvm_deliver_exception_payload
to update DR6.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/kvm_host.h | 2 +
arch/x86/kvm/svm/nested.c | 136 +++++++++++++-------------------
arch/x86/kvm/svm/svm.c | 9 ---
arch/x86/kvm/svm/svm.h | 1 +
arch/x86/kvm/x86.c | 13 +--
5 files changed, 58 insertions(+), 103 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7707bd4b0593..e6f2e1a2dab6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1495,6 +1495,8 @@ void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id);

void kvm_inject_nmi(struct kvm_vcpu *vcpu);

+void kvm_update_dr7(struct kvm_vcpu *vcpu);
+
int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index d544cce4f964..87fc5879dfaa 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -111,6 +111,8 @@ void recalc_intercepts(struct vcpu_svm *svm)
h = &svm->nested.hsave->control;
g = &svm->nested;

+ svm->nested.host_intercept_exceptions = h->intercept_exceptions;
+
c->intercept_cr = h->intercept_cr;
c->intercept_dr = h->intercept_dr;
c->intercept_exceptions = h->intercept_exceptions;
@@ -616,50 +618,6 @@ static int nested_svm_exit_handled_msr(struct vcpu_svm *svm)
return (value & mask) ? NESTED_EXIT_DONE : NESTED_EXIT_HOST;
}

-/* DB exceptions for our internal use must not cause vmexit */
-static int nested_svm_intercept_db(struct vcpu_svm *svm)
-{
- unsigned long dr6 = svm->vmcb->save.dr6;
-
- /* Always catch it and pass it to userspace if debugging. */
- if (svm->vcpu.guest_debug &
- (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
- return NESTED_EXIT_HOST;
-
- /* if we're not singlestepping, it's not ours */
- if (!svm->nmi_singlestep)
- goto reflected_db;
-
- /* if it's not a singlestep exception, it's not ours */
- if (!(dr6 & DR6_BS))
- goto reflected_db;
-
- /* if the guest is singlestepping, it should get the vmexit */
- if (svm->nmi_singlestep_guest_rflags & X86_EFLAGS_TF) {
- disable_nmi_singlestep(svm);
- goto reflected_db;
- }
-
- /* it's ours, the nested hypervisor must not see this one */
- return NESTED_EXIT_HOST;
-
-reflected_db:
- /*
- * Synchronize guest DR6 here just like in kvm_deliver_exception_payload;
- * it will be moved into the nested VMCB by nested_svm_vmexit. Once
- * exceptions will be moved to svm_check_nested_events, all this stuff
- * will just go away and we could just return NESTED_EXIT_HOST
- * unconditionally. db_interception will queue the exception, which
- * will be processed by svm_check_nested_events if a nested vmexit is
- * required, and we will just use kvm_deliver_exception_payload to copy
- * the payload to DR6 before vmexit.
- */
- WARN_ON(svm->vcpu.arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT);
- svm->vcpu.arch.dr6 &= ~(DR_TRAP_BITS | DR6_RTM);
- svm->vcpu.arch.dr6 |= dr6 & ~DR6_FIXED_1;
- return NESTED_EXIT_DONE;
-}
-
static int nested_svm_intercept_ioio(struct vcpu_svm *svm)
{
unsigned port, size, iopm_len;
@@ -710,20 +668,12 @@ static int nested_svm_intercept(struct vcpu_svm *svm)
break;
}
case SVM_EXIT_EXCP_BASE ... SVM_EXIT_EXCP_BASE + 0x1f: {
- u32 excp_bits = 1 << (exit_code - SVM_EXIT_EXCP_BASE);
- if (svm->nested.intercept_exceptions & excp_bits) {
- if (exit_code == SVM_EXIT_EXCP_BASE + DB_VECTOR)
- vmexit = nested_svm_intercept_db(svm);
- else if (exit_code == SVM_EXIT_EXCP_BASE + BP_VECTOR &&
- svm->vcpu.guest_debug & KVM_GUESTDBG_USE_SW_BP)
- vmexit = NESTED_EXIT_HOST;
- else
- vmexit = NESTED_EXIT_DONE;
- }
- /* async page fault always cause vmexit */
- else if ((exit_code == SVM_EXIT_EXCP_BASE + PF_VECTOR) &&
- svm->vcpu.arch.exception.nested_apf != 0)
- vmexit = NESTED_EXIT_DONE;
+ /*
+ * Host-intercepted exceptions have been checked already in
+ * nested_svm_exit_special. There is nothing to do here,
+ * the vmexit is injected by svm_check_nested_events.
+ */
+ vmexit = NESTED_EXIT_DONE;
break;
}
case SVM_EXIT_ERR: {
@@ -768,35 +718,45 @@ int nested_svm_check_permissions(struct vcpu_svm *svm)
return 0;
}

-int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
- bool has_error_code, u32 error_code)
+static bool nested_exit_on_exception(struct vcpu_svm *svm)
{
- int vmexit;
+ unsigned int nr = svm->vcpu.arch.exception.nr;

- if (!is_guest_mode(&svm->vcpu))
- return 0;
+ return (svm->nested.intercept_exceptions & (1 << nr));
+}

- vmexit = nested_svm_intercept(svm);
- if (vmexit != NESTED_EXIT_DONE)
- return 0;
+static void nested_svm_inject_exception_vmexit(struct vcpu_svm *svm)
+{
+ unsigned int nr = svm->vcpu.arch.exception.nr;

svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + nr;
svm->vmcb->control.exit_code_hi = 0;
- svm->vmcb->control.exit_info_1 = error_code;
+
+ if (svm->vcpu.arch.exception.has_error_code)
+ svm->vmcb->control.exit_info_1 = svm->vcpu.arch.exception.error_code;

/*
* EXITINFO2 is undefined for all exception intercepts other
* than #PF.
*/
- if (svm->vcpu.arch.exception.nested_apf)
- svm->vmcb->control.exit_info_2 = svm->vcpu.arch.apf.nested_apf_token;
- else if (svm->vcpu.arch.exception.has_payload)
- svm->vmcb->control.exit_info_2 = svm->vcpu.arch.exception.payload;
- else
- svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
+ if (nr == PF_VECTOR) {
+ if (svm->vcpu.arch.exception.nested_apf)
+ svm->vmcb->control.exit_info_2 = svm->vcpu.arch.apf.nested_apf_token;
+ else if (svm->vcpu.arch.exception.has_payload)
+ svm->vmcb->control.exit_info_2 = svm->vcpu.arch.exception.payload;
+ else
+ svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
+ } else if (nr == DB_VECTOR) {
+ /* See inject_pending_event. */
+ kvm_deliver_exception_payload(&svm->vcpu);
+ if (svm->vcpu.arch.dr7 & DR7_GD) {
+ svm->vcpu.arch.dr7 &= ~DR7_GD;
+ kvm_update_dr7(&svm->vcpu);
+ }
+ } else
+ WARN_ON(svm->vcpu.arch.exception.has_payload);

- svm->nested.exit_required = true;
- return vmexit;
+ nested_svm_vmexit(svm);
}

static void nested_svm_smi(struct vcpu_svm *svm)
@@ -835,6 +795,15 @@ static int svm_check_nested_events(struct kvm_vcpu *vcpu)
kvm_event_needs_reinjection(vcpu) || svm->nested.exit_required ||
svm->nested.nested_run_pending;

+ if (vcpu->arch.exception.pending) {
+ if (block_nested_events)
+ return -EBUSY;
+ if (!nested_exit_on_exception(svm))
+ return 0;
+ nested_svm_inject_exception_vmexit(svm);
+ return 0;
+ }
+
if (vcpu->arch.smi_pending && !svm_smi_blocked(vcpu)) {
if (block_nested_events)
return -EBUSY;
@@ -872,18 +841,19 @@ int nested_svm_exit_special(struct vcpu_svm *svm)
switch (exit_code) {
case SVM_EXIT_INTR:
case SVM_EXIT_NMI:
- case SVM_EXIT_EXCP_BASE + MC_VECTOR:
- return NESTED_EXIT_HOST;
case SVM_EXIT_NPF:
- /* For now we are always handling NPFs when using them */
- if (npt_enabled)
+ return NESTED_EXIT_HOST;
+ case SVM_EXIT_EXCP_BASE ... SVM_EXIT_EXCP_BASE + 0x1f: {
+ u32 excp_bits = 1 << (exit_code - SVM_EXIT_EXCP_BASE);
+
+ if (get_host_vmcb(svm)->control.intercept_exceptions & excp_bits)
return NESTED_EXIT_HOST;
- break;
- case SVM_EXIT_EXCP_BASE + PF_VECTOR:
- /* Trap async PF even if not shadowing */
- if (!npt_enabled || svm->vcpu.arch.apf.host_apf_reason)
+ else if (exit_code == SVM_EXIT_EXCP_BASE + PF_VECTOR &&
+ svm->vcpu.arch.apf.host_apf_reason)
+ /* Trap async PF even if not shadowing */
return NESTED_EXIT_HOST;
break;
+ }
default:
break;
}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9ac9963405b5..251c457820a1 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -331,17 +331,8 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu)
struct vcpu_svm *svm = to_svm(vcpu);
unsigned nr = vcpu->arch.exception.nr;
bool has_error_code = vcpu->arch.exception.has_error_code;
- bool reinject = vcpu->arch.exception.injected;
u32 error_code = vcpu->arch.exception.error_code;

- /*
- * If we are within a nested VM we'd better #VMEXIT and let the guest
- * handle the exception
- */
- if (!reinject &&
- nested_svm_check_exception(svm, nr, has_error_code, error_code))
- return;
-
kvm_deliver_exception_payload(&svm->vcpu);

if (nr == BP_VECTOR && !nrips) {
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 5cc559ab862d..8342032291fc 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -86,6 +86,7 @@ struct nested_state {
u64 hsave_msr;
u64 vm_cr_msr;
u64 vmcb;
+ u32 host_intercept_exceptions;

/* These are the merged vectors */
u32 *msrpm;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 192238841cac..e03543488d37 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1072,7 +1072,7 @@ static void kvm_update_dr0123(struct kvm_vcpu *vcpu)
}
}

-static void kvm_update_dr7(struct kvm_vcpu *vcpu)
+void kvm_update_dr7(struct kvm_vcpu *vcpu)
{
unsigned long dr7;

@@ -1085,6 +1085,7 @@ static void kvm_update_dr7(struct kvm_vcpu *vcpu)
if (dr7 & DR7_BP_EN_MASK)
vcpu->arch.switch_db_regs |= KVM_DEBUGREG_BP_ENABLED;
}
+EXPORT_SYMBOL_GPL(kvm_update_dr7);

static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)
{
@@ -7774,16 +7775,6 @@ static void inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit
X86_EFLAGS_RF);

if (vcpu->arch.exception.nr == DB_VECTOR) {
- /*
- * This code assumes that nSVM doesn't use
- * check_nested_events(). If it does, the
- * DR6/DR7 changes should happen before L1
- * gets a #VMEXIT for an intercepted #DB in
- * L2. (Under VMX, on the other hand, the
- * DR6/DR7 changes should not happen in the
- * event of a VM-exit to L1 for an intercepted
- * #DB in L2.)
- */
kvm_deliver_exception_payload(vcpu);
if (vcpu->arch.dr7 & DR7_GD) {
vcpu->arch.dr7 &= ~DR7_GD;
--
2.26.2

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