From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
"Julien Grall" <julien@xen.org>, "Wei Liu" <wl@xen.org>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH] VMX: use a single, global APIC access page
Date: Wed, 10 Feb 2021 17:00:18 +0000 [thread overview]
Message-ID: <3c7a4cff-3f11-22e1-ed46-e76f62cc08f4@citrix.com> (raw)
In-Reply-To: <1b6a411b-84e7-bfb1-647e-511a13df838c@suse.com>
On 10/02/2021 16:48, Jan Beulich wrote:
> The address of this page is used by the CPU only to recognize when to
> instead access the virtual APIC page instead. No accesses would ever go
> to this page. It only needs to be present in the (CPU) page tables so
> that address translation will produce its address as result for
> respective accesses.
>
> By making this page global, we also eliminate the need to refcount it,
> or to assign it to any domain in the first place.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
How certain are you about this?
It's definitely not true on AMD's AVIC - writes very definitely end up
in the backing page if they miss the APIC registers.
This concern was why we didn't use a global page originally, IIRC.
~Andrew
next prev parent reply other threads:[~2021-02-10 17:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-10 16:48 [PATCH] VMX: use a single, global APIC access page Jan Beulich
2021-02-10 17:00 ` Andrew Cooper [this message]
2021-02-10 17:03 ` Jan Beulich
2021-03-01 2:08 ` Tian, Kevin
2021-02-10 17:16 ` Jan Beulich
2021-02-11 8:45 ` Roger Pau Monné
2021-02-11 10:36 ` Jan Beulich
2021-02-11 11:16 ` Roger Pau Monné
2021-02-11 11:22 ` Jan Beulich
2021-02-11 12:27 ` Roger Pau Monné
2021-03-01 2:18 ` Tian, Kevin
2021-03-01 8:15 ` Jan Beulich
2021-03-01 8:30 ` Tian, Kevin
2021-03-01 9:58 ` Jan Beulich
2021-03-04 7:51 ` Tian, Kevin
2021-02-11 13:53 ` Andrew Cooper
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