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Message-Id: <20200516135311.704878-3-pbonzini@redhat.com>
Date: Sat, 16 May 2020 09:53:09 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: peterx@...hat.com
Subject: [PATCH 2/4] KVM: nSVM: inject exceptions via svm_check_nested_events
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@...hat.com>
---
arch/x86/kvm/svm/nested.c | 129 ++++++++++++++------------------------
arch/x86/kvm/svm/svm.c | 9 ---
arch/x86/kvm/svm/svm.h | 1 +
3 files changed, 47 insertions(+), 92 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index e98ce5f6d562..35ce3bef0a9a 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;
@@ -625,50 +627,6 @@ 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;
@@ -719,20 +677,12 @@ 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: {
@@ -777,35 +727,38 @@ 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 (svm->vcpu.arch.exception.has_payload)
+ kvm_deliver_exception_payload(&svm->vcpu);
- svm->nested.exit_required = true;
- return vmexit;
+ nested_svm_vmexit(svm);
}
static void nested_svm_smi(struct vcpu_svm *svm)
@@ -844,6 +797,15 @@ 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;
@@ -881,18 +843,19 @@ 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 (svm->nested.host_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 95d16aa76ebb..851484abafe6 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 39706aa845f2..1fb23a2cdf8b 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;
--
2.18.2
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