From: "Roger Pau Monné" <roger.pau@citrix.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
Ian Jackson <iwj@xenproject.org>
Subject: Re: [PATCH][4.15] x86: mirror compat argument translation area for 32-bit PV
Date: Mon, 22 Feb 2021 15:13:28 +0100 [thread overview]
Message-ID: <YDO8CM0prPjoo/X1@Air-de-Roger> (raw)
In-Reply-To: <YDOW+ftkNsG2RH3C@Air-de-Roger>
On Mon, Feb 22, 2021 at 12:35:21PM +0100, Roger Pau Monné wrote:
> On Mon, Feb 22, 2021 at 11:27:07AM +0100, Jan Beulich wrote:
> > Now that we guard the entire Xen VA space against speculative abuse
> > through hypervisor accesses to guest memory, the argument translation
> > area's VA also needs to live outside this range, at least for 32-bit PV
> > guests. To avoid extra is_hvm_*() conditionals, use the alternative VA
> > uniformly.
>
> Since you are double mapping the per-domain virtual area, won't it
> make more sense to map it just once outside of the Xen virtual space
> area? (so it's always using PML4_ADDR(511))
Right, that's not possible for PV 64bit domains because it's guest
owned linear address space in that case.
It seems like paravirt_ctxt_switch_to will modify the root_pgt to set
the PERDOMAIN_VIRT_START entry, does the same need to be done for
PERDOMAIN2_VIRT_START?
I would also consider giving the slot a more meaningful name, as
PERDOMAIN2_VIRT_START makes it seem like a new per-domain scratch
space, when it's just a different mapping of the existing physical
memory.
Maybe PERDOMAIN_MIRROR_VIRT_START? Or PERDOMAIN_XLAT_VIRT_START?
Thanks, Roger.
next prev parent reply other threads:[~2021-02-22 14:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-22 10:27 [PATCH][4.15] x86: mirror compat argument translation area for 32-bit PV Jan Beulich
2021-02-22 11:26 ` Ian Jackson
2021-02-22 11:35 ` Roger Pau Monné
2021-02-22 14:12 ` Jan Beulich
2021-02-22 14:13 ` Roger Pau Monné [this message]
2021-02-22 14:20 ` Jan Beulich
2021-02-22 14:46 ` Roger Pau Monné
2021-02-22 14:14 ` Andrew Cooper
2021-02-22 14:22 ` Jan Beulich
2021-02-22 16:47 ` Andrew Cooper
2021-02-22 19:36 ` Roger Pau Monné
2021-02-23 7:13 ` Jan Beulich
2021-02-24 19:04 ` Andrew Cooper
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