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KVM: nSVM: inject exceptions via svm_check_nested_events

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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>
This commit is contained in:
Paolo Bonzini 2020-05-16 08:42:28 -04:00
parent c9d40913ac
commit 7c86663b68
5 changed files with 59 additions and 104 deletions
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2
arch/x86/include/asm/kvm_host.h
View File

@ -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);

138
arch/x86/kvm/svm/nested.c
View File

@ -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;
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)
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;
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;
}

9
arch/x86/kvm/svm/svm.c
View File

@ -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) {

1
arch/x86/kvm/svm/svm.h
View File

@ -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;

13
arch/x86/kvm/x86.c
View File

@ -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)
{
@ -7778,16 +7779,6 @@ 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;