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From c31315e765df0137cb7dfedb3869db72d6d2ca57 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Mon, 22 Jul 2019 18:22:10 +0100
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Subject: [PATCH 29/39] target/i386: kvm: Re-inject #DB to guest with updated
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DR6
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <20190722182220.19374-9-pbonzini@redhat.com>
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Patchwork-id: 89626
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O-Subject: [RHEL-8.1.0 PATCH qemu-kvm v3 08/18] target/i386: kvm: Re-inject #DB to guest with updated DR6
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Bugzilla: 1689269
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RH-Acked-by: Peter Xu <zhexu@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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From: Liran Alon <liran.alon@oracle.com>
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If userspace (QEMU) debug guest, when #DB is raised in guest and
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intercepted by KVM, KVM forwards information on #DB to userspace
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instead of injecting #DB to guest.
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While doing so, KVM don't update vCPU DR6 but instead report the #DB DR6
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value to userspace for further handling.
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See KVM's handle_exception() DB_VECTOR handler.
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QEMU handler for this case is kvm_handle_debug(). This handler basically
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checks if #DB is related to one of user set hardware breakpoints and if
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not, it re-inject #DB into guest.
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The re-injection is done by setting env->exception_injected to #DB which
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will later be passed as events.exception.nr to KVM_SET_VCPU_EVENTS ioctl
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by kvm_put_vcpu_events().
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However, in case userspace re-injects #DB, KVM expects userspace to set
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vCPU DR6 as reported to userspace when #DB was intercepted! Otherwise,
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KVM_REQ_EVENT handler will inject #DB with wrong DR6 to guest.
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Fix this issue by updating vCPU DR6 appropriately when re-inject #DB to
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guest.
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Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
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Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
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Signed-off-by: Liran Alon <liran.alon@oracle.com>
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Message-Id: <20190619162140.133674-5-liran.alon@oracle.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit bceeeef9e7544057659118688243260c390eceb9)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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target/i386/kvm.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/target/i386/kvm.c b/target/i386/kvm.c
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index 4138fe9..1a4ff3c 100644
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--- a/target/i386/kvm.c
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+++ b/target/i386/kvm.c
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@@ -3363,6 +3363,9 @@ static int kvm_handle_debug(X86CPU *cpu,
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/* pass to guest */
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env->exception_injected = arch_info->exception;
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env->has_error_code = 0;
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+ if (arch_info->exception == EXCP01_DB) {
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+ env->dr[6] = arch_info->dr6;
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+ }
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}
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return ret;
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--
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1.8.3.1
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