[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 1/3] x86/HVM: permit CLFLUSH{,OPT} on execute-only code segments
- To: Andrew Cooper <amc96@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 3 Dec 2021 12:55:58 +0100
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=suse.com; dmarc=pass action=none header.from=suse.com; dkim=pass header.d=suse.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=gVXn41K2c2U1kGH5e7upCj/T3lY72QTk8lKOWSWrFDY=; b=YKdCYMxeHqxHaWiItMiEODWFbgchR29nHb7eFjEZSEOHg1VC4PiyyLcw96m2hkCp2r3tcqNFDnaOjSP1itSbYp7P7o50hTDRL7+D8xbnBkOUSp7QBsN259a82T1Cv8hUMxXIw5xWiaN2lPy2TilscjkW9QY7h+YU89vzfuh0/6NQFUIBkOtta4G5UYfD2+EkEV6XQ3qfNl9p9Pq42iE29iop6bkKA+EG3H0WUmasMwlZ1FH/woBHmeGOdIyAV8i4HZtrJhjZNOtHJMEj1pvE/3ypmO8ObmToJnDLrbRywEta1C50LVDgBWbIhl0n7/1Mg4urwQW3DbVWbQfocFI0Ug==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=LXpJYtAYhzw0CWJAq4mSvPzLrfq9+MEFpvGPsNfXmRQGAdCnhc8VY+57CHWE/DhWfjtQKVbdwsZQBA4sYYPhOJKH3kXBVOtjWywx28hJDVJQ6euVs/g4aoblWnLda4aaTdU2Cp5AFglXmWBgxDcvRKk62KLgYRFe3ZXbzgolZ5lB8zb1O3W1eZQXFaLh8JzCT27gXTuoG4k3zABKq05Hj+C4HwCO9/ZTII1zRb0KtO+5iSKRKf44vgGUeJY/NV5BH5oFPH7x31gkAmYcs3jNgV6GYrcKMkWVqFc2dQDMR9g2Ujz0k17l+cgfuwKvj6cs7QvZ2sqzc4arackn3AsCrg==
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=suse.com;
- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>
- Delivery-date: Fri, 03 Dec 2021 11:56:31 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 03.12.2021 12:48, Andrew Cooper wrote:
> On 03/12/2021 11:21, Jan Beulich wrote:
>> The SDM explicitly permits this, and since that's sensible behavior
>> don't special case AMD (where the PM doesn't explicitly say so).
>
> APM explicitly says so too.
>
> "The CLFLUSH instruction executes at any privilege level. CLFLUSH
> performs all the segmentation and paging checks that a 1-byte read would
> perform, except that it also allows references to execute-only segments."
>
> and
>
> "The CLFLUSHOPT instruction executes at any privilege level. CLFLUSHOPT
> performs all the segmentation and paging checks that a 1-byte read would
> perform, except that it also allows references to execute-only segments."
Somehow I didn't read further after the page table related paragraph,
perhaps on the assumption that like in the SDM it would be all in one
paragraph.
>> Fixes: 52dba7bd0b36 ("x86emul: generalize wbinvd() hook")
>> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> With the commit message tweaked, Reviewed-by: Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>. Far less invasive than I was fearing.
Thanks. I've switched to simply saying "Both SDM and PM explicitly
permit this."
Jan
|
