linux-kernel - Re: [PATCH v2 06/21] KVM: x86: Treat #DBs from the emulator as fault-like (code and DR7.GD=1)

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Message-ID: <CALMp9eS+54W=w=0UXRvB95OprNbpte=_TDu=c9qzcY0kyRqbuQ@mail.gmail.com>
Date:   Wed, 6 Jul 2022 16:55:35 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Oliver Upton <oupton@...gle.com>,
        Peter Shier <pshier@...gle.com>
Subject: Re: [PATCH v2 06/21] KVM: x86: Treat #DBs from the emulator as
 fault-like (code and DR7.GD=1)

On Tue, Jun 14, 2022 at 1:47 PM Sean Christopherson <seanjc@...gle.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?
Are there KVM errata for those misbehaviors?
What about single-stepping? Is that handled outwith the emulator?