From c31315e765df0137cb7dfedb3869db72d6d2ca57 Mon Sep 17 00:00:00 2001

From: Paolo Bonzini <pbonzini@redhat.com>

Date: Mon, 22 Jul 2019 18:22:10 +0100

Subject: [PATCH 29/39] target/i386: kvm: Re-inject #DB to guest with updated

 DR6

RH-Author: Paolo Bonzini <pbonzini@redhat.com>

Message-id: <20190722182220.19374-9-pbonzini@redhat.com>

Patchwork-id: 89626

O-Subject: [RHEL-8.1.0 PATCH qemu-kvm v3 08/18] target/i386: kvm: Re-inject #DB to guest with updated DR6

Bugzilla: 1689269

RH-Acked-by: Peter Xu <zhexu@redhat.com>

RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

From: Liran Alon <liran.alon@oracle.com>

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 <nikita.leshchenko@oracle.com>

Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>

Signed-off-by: Liran Alon <liran.alon@oracle.com>

Message-Id: <20190619162140.133674-5-liran.alon@oracle.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit bceeeef9e7544057659118688243260c390eceb9)

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 target/i386/kvm.c | 3 +++

 1 file changed, 3 insertions(+)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c

index 4138fe9..1a4ff3c 100644

--- a/target/i386/kvm.c

+++ b/target/i386/kvm.c

@@ -3363,6 +3363,9 @@ 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;

-- 

1.8.3.1