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KVM: SVM: keep DR6 synchronized with vcpu->arch.dr6

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kvm_x86_ops.set_dr6 is only ever called with vcpu->arch.dr6 as the
second argument.  Ensure that the VMCB value is synchronized to
vcpu->arch.dr6 on #DB (both "normal" and nested) and nested vmentry, so
that the current value of DR6 is always available in vcpu->arch.dr6.
The get_dr6 callback can just access vcpu->arch.dr6 and becomes redundant.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini
2020-05-04 11:28:25 -04:00
parent 2c19dba680
commit 5679b803e4
5 changed files with 21 additions and 28 deletions
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24
arch/x86/kvm/svm/nested.c
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@@ -19,6 +19,7 @@
#include <linux/kernel.h>
#include <asm/msr-index.h>
#include <asm/debugreg.h>
#include "kvm_emulate.h"
#include "trace.h"
@@ -267,7 +268,8 @@ void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
svm->vmcb->save.rsp = nested_vmcb->save.rsp;
svm->vmcb->save.rip = nested_vmcb->save.rip;
svm->vmcb->save.dr7 = nested_vmcb->save.dr7;
svm->vmcb->save.dr6 = nested_vmcb->save.dr6;
svm->vcpu.arch.dr6 = nested_vmcb->save.dr6;
kvm_update_dr6(&svm->vcpu);
svm->vmcb->save.cpl = nested_vmcb->save.cpl;
svm->nested.vmcb_msrpm = nested_vmcb->control.msrpm_base_pa & ~0x0fffULL;
@@ -482,7 +484,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
nested_vmcb->save.rsp = vmcb->save.rsp;
nested_vmcb->save.rax = vmcb->save.rax;
nested_vmcb->save.dr7 = vmcb->save.dr7;
nested_vmcb->save.dr6 = vmcb->save.dr6;
nested_vmcb->save.dr6 = svm->vcpu.arch.dr6;
nested_vmcb->save.cpl = vmcb->save.cpl;
nested_vmcb->control.int_ctl = vmcb->control.int_ctl;
@@ -606,7 +608,7 @@ static int nested_svm_exit_handled_msr(struct vcpu_svm *svm)
/* DB exceptions for our internal use must not cause vmexit */
static int nested_svm_intercept_db(struct vcpu_svm *svm)
{
unsigned long dr6;
unsigned long dr6 = svm->vmcb->save.dr6;
/* Always catch it and pass it to userspace if debugging. */
if (svm->vcpu.guest_debug &
@@ -615,22 +617,28 @@ static int nested_svm_intercept_db(struct vcpu_svm *svm)
/* if we're not singlestepping, it's not ours */
if (!svm->nmi_singlestep)
return NESTED_EXIT_DONE;
goto reflected_db;
/* if it's not a singlestep exception, it's not ours */
if (kvm_get_dr(&svm->vcpu, 6, &dr6))
return NESTED_EXIT_DONE;
if (!(dr6 & DR6_BS))
return NESTED_EXIT_DONE;
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);
return NESTED_EXIT_DONE;
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 db_interception; it will
* be moved into the nested VMCB by nested_svm_vmexit.
*/
svm->vcpu.arch.dr6 = dr6;
return NESTED_EXIT_DONE;
}
static int nested_svm_intercept_ioio(struct vcpu_svm *svm)