From: Josh Poimboeuf <jpoimboe@kernel.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
pbonzini@redhat.com, x86@kernel.org
Subject: Re: VMX HOST_RIP target alignment
Date: Thu, 17 Nov 2022 15:22:08 -0800 [thread overview]
Message-ID: <20221117232208.26ha4tjizeegcbwr@treble> (raw)
In-Reply-To: <Y3adkSe/J70PqUyt@p183>
On Thu, Nov 17, 2022 at 11:46:09PM +0300, Alexey Dobriyan wrote:
> One of the side effects of fixing retbleed for VMX was demoting
> HOST_RIP target from honorable function to a lowly label:
>
> -SYM_FUNC_START(vmx_vmexit)
> +SYM_INNER_LABEL(vmx_vmexit, SYM_L_GLOBAL)
>
> ffffffff81243c49: 0f 01 c2 vmlaunch
> ffffffff81243c4c: e9 a7 00 00 00 jmp ffffffff81243cf8 <vmx_vmexit+0xa7>
>
> ffffffff81243c51 <vmx_vmexit>:
> ffffffff81243c51: 50 push rax
>
> Now I've never measured VM exit latency but is it important to align it
> at 16 bytes like Intel recommends for functions?
Yes, I'd think we should restore the alignment to 16 bytes again, that
change was definitely not intentional.
--
Josh
prev parent reply other threads:[~2022-11-17 23:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-17 20:46 VMX HOST_RIP target alignment Alexey Dobriyan
2022-11-17 23:22 ` Josh Poimboeuf [this message]
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