From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] x86/shim: Simplify compat handling in write_start_info()
Date: Mon, 19 Apr 2021 16:57:04 +0100 [thread overview]
Message-ID: <faff3047-66e3-0d6f-1878-e1dac47b7c06@citrix.com> (raw)
In-Reply-To: <a048d155-085d-b942-40cc-00624b5bbd11@suse.com>
On 19/04/2021 16:55, Jan Beulich wrote:
> On 19.04.2021 16:45, Andrew Cooper wrote:
>> Factor out a compat boolean to remove the lfence overhead from multiple
>> is_pv_32bit_domain() calls.
>>
>> For a compat guest, the upper 32 bits of rdx are zero, so there is no need to
>> have any conditional logic at all when mapping the start info page.
> Iirc the contents of the upper halves hold unspecified contents after
> a switch from compat to 64-bit mode. Therefore only with this part of
> the change dropped ...
But we're shim, so will never ever mix compat and non-compat guests.
~Andrew
>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>
> Jan
next prev parent reply other threads:[~2021-04-19 15:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 14:45 [PATCH] x86/shim: Simplify compat handling in write_start_info() Andrew Cooper
2021-04-19 15:55 ` Jan Beulich
2021-04-19 15:57 ` Andrew Cooper [this message]
2021-04-19 16:00 ` Jan Beulich
2021-04-20 17:37 ` Andrew Cooper
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