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Date:   Thu, 7 Jul 2022 17:19:56 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Jim Mattson <jmattson@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Oliver Upton <oupton@google.com>,
        Peter Shier <pshier@google.com>
Subject: Re: [PATCH v2 06/21] KVM: x86: Treat #DBs from the emulator as
 fault-like (code and DR7.GD=1)
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References: <20220614204730.3359543-1-seanjc@google.com>
 <20220614204730.3359543-7-seanjc@google.com>
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On Wed, Jul 06, 2022, Jim Mattson wrote:
> On Tue, Jun 14, 2022 at 1:47 PM Sean Christopherson <seanjc@google.com> wrote:
> >
> > Add a dedicated "exception type" for #DBs, as #DBs can be fault-like or
> > trap-like depending the sub-type of #DB, and effectively defer the
> > decision of what to do with the #DB to the caller.
> >
> > For the emulator's two calls to exception_type(), treat the #DB as
> > fault-like, as the emulator handles only code breakpoint and general
> > detect #DBs, both of which are fault-like.
> 
> Does this mean that data and I/O breakpoint traps are just dropped?

Yep.

> Are there KVM errata for those misbehaviors?

Nope.

> What about single-stepping? Is that handled outwith the emulator?

Single-step is emulated, and AFAIK there are no _known_ bugs.