From: linmiaohe <linmiaohe@huawei.com>
To: Peter Xu <peterx@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH] KVM: X86: Avoid explictly fetch instruction in x86_decode_insn()
Date: Wed, 4 Mar 2020 02:37:06 +0000 [thread overview]
Message-ID: <05ca4e7e070844dd92e4f673a1bc15d9@huawei.com> (raw)
Hi:
Peter Xu <peterx@redhat.com> writes:
>insn_fetch() will always implicitly refill instruction buffer properly when the buffer is empty, so we don't need to explicitly fetch it even if insn_len==0 for x86_decode_insn().
>
>Signed-off-by: Peter Xu <peterx@redhat.com>
>---
> arch/x86/kvm/emulate.c | 5 -----
> 1 file changed, 5 deletions(-)
>
>diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index dd19fb3539e0..04f33c1ca926 100644
>--- a/arch/x86/kvm/emulate.c
>+++ b/arch/x86/kvm/emulate.c
>@@ -5175,11 +5175,6 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
> ctxt->opcode_len = 1;
> if (insn_len > 0)
> memcpy(ctxt->fetch.data, insn, insn_len);
>- else {
>- rc = __do_insn_fetch_bytes(ctxt, 1);
>- if (rc != X86EMUL_CONTINUE)
>- goto done;
>- }
>
> switch (mode) {
> case X86EMUL_MODE_REAL:
Looks good, thanks. But it seems we should also take care of the comment in __do_insn_fetch_bytes(), as we do not
load instruction at the beginning of x86_decode_insn() now, which may be misleading:
/*
* One instruction can only straddle two pages,
* and one has been loaded at the beginning of
* x86_decode_insn. So, if not enough bytes
* still, we must have hit the 15-byte boundary.
*/
if (unlikely(size < op_size))
return emulate_gp(ctxt, 0);
next reply other threads:[~2020-03-04 2:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 2:37 linmiaohe [this message]
2020-03-04 7:30 ` [PATCH] KVM: X86: Avoid explictly fetch instruction in x86_decode_insn() Paolo Bonzini
2020-03-04 15:18 ` Peter Xu
2020-03-04 15:32 ` Peter Xu
2020-03-04 18:19 ` Paolo Bonzini
2020-03-04 20:30 ` Nadav Amit
-- strict thread matches above, loose matches on Subject: below --
2020-03-04 2:16 Peter Xu
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=05ca4e7e070844dd92e4f673a1bc15d9@huawei.com \
--to=linmiaohe@huawei.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=peterx@redhat.com \
--cc=sean.j.christopherson@intel.com \
--cc=vkuznets@redhat.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).