From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH] KVM: x86: Add kvm_x86_ops hook to short circuit emulation
Date: Tue, 22 Sep 2020 15:32:14 +0200 [thread overview]
Message-ID: <0fe8dc75-4aa3-cd84-5fff-1d2f23c01c6a@redhat.com> (raw)
In-Reply-To: <20200915232702.15945-1-sean.j.christopherson@intel.com>
On 16/09/20 01:27, Sean Christopherson wrote:
> Replace the existing kvm_x86_ops.need_emulation_on_page_fault() with a
> more generic is_emulatable(), and unconditionally call the new function
> in x86_emulate_instruction().
>
> KVM will use the generic hook to support multiple security related
> technologies that prevent emulation in one way or another. Similar to
> the existing AMD #NPF case where emulation of the current instruction is
> not possible due to lack of information, AMD's SEV-ES and Intel's SGX
> and TDX will introduce scenarios where emulation is impossible due to
> the guest's register state being inaccessible. And again similar to the
> existing #NPF case, emulation can be initiated by kvm_mmu_page_fault(),
> i.e. outside of the control of vendor-specific code.
>
> While the cause and architecturally visible behavior of the various
> cases are different, e.g. SGX will inject a #UD, AMD #NPF is a clean
> resume or complete shutdown, and SEV-ES and TDX "return" an error, the
> impact on the common emulation code is identical: KVM must stop
> emulation immediately and resume the guest.
>
> Query is_emulatable() in handle_ud() as well so that the
> force_emulation_prefix code doesn't incorrectly modify RIP before
> calling emulate_instruction() in the absurdly unlikely scenario that
> KVM encounters forced emulation in conjunction with "do not emulate".
Ahah, I love those adverb + adjective pairs (my favorite is
https://patchwork.kernel.org/cover/10710751/ which unfortunately was in
the cover letter and thus was not immortalized in linux.git).
"is_emulatable" is not very grammatical, so I'd rather call it
"can_emulate_instruction" instead. Either way, it's an improvement over
"need". Queued, thanks.
Paolo
prev parent reply other threads:[~2020-09-22 13:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 23:27 [PATCH] KVM: x86: Add kvm_x86_ops hook to short circuit emulation Sean Christopherson
2020-09-16 1:31 ` Wanpeng Li
2020-09-16 17:34 ` Sean Christopherson
2020-09-22 13:32 ` Paolo Bonzini
2020-09-30 1:43 ` Sean Christopherson
2020-09-22 13:32 ` Paolo Bonzini [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0fe8dc75-4aa3-cd84-5fff-1d2f23c01c6a@redhat.com \
--to=pbonzini@redhat.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sean.j.christopherson@intel.com \
--cc=thomas.lendacky@amd.com \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).