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[Qemu-devel] [PATCH 2/7] KVM: i386: Re-inject #DB to guest with updated
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 2/7] KVM: i386: Re-inject #DB to guest with updated DR6 |
Date: |
Sat, 15 Jun 2019 02:42:51 +0200 |
From: Liran Alon <address@hidden>
If userspace (QEMU) debug guest, when #DB is raised in guest and
intercepted by KVM, KVM forwards information on #DB to userspace
instead of injecting #DB to guest.
While doing so, KVM don't update vCPU DR6 but instead report the #DB DR6
value to userspace for further handling.
See KVM's handle_exception() DB_VECTOR handler.
QEMU handler for this case is kvm_handle_debug(). This handler basically
checks if #DB is related to one of user set hardware breakpoints and if
not, it re-inject #DB into guest.
The re-injection is done by setting env->exception_injected to #DB which
will later be passed as events.exception.nr to KVM_SET_VCPU_EVENTS ioctl
by kvm_put_vcpu_events().
However, in case userspace re-injects #DB, KVM expects userspace to set
vCPU DR6 as reported to userspace when #DB was intercepted! Otherwise,
KVM_REQ_EVENT handler will inject #DB with wrong DR6 to guest.
Fix this issue by updating vCPU DR6 appropriately when re-inject #DB to
guest.
Reviewed-by: Nikita Leshenko <address@hidden>
Signed-off-by: Liran Alon <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
target/i386/kvm.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index c8d8196e71..53f95b02a0 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -3546,6 +3546,9 @@ static int kvm_handle_debug(X86CPU *cpu,
/* pass to guest */
env->exception_injected = arch_info->exception;
env->has_error_code = 0;
+ if (arch_info->exception == EXCP01_DB) {
+ env->dr[6] = arch_info->dr6;
+ }
}
return ret;
--
2.21.0
[Qemu-devel] [PATCH 7/7] Revert "target/i386: kvm: add VMX migration blocker", Paolo Bonzini, 2019/06/14