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From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH 7/8] xen/x86: Rework CR4 handling for PV guests
Date: Fri, 26 Jun 2015 09:50:05 +0100	[thread overview]
Message-ID: <558D2E5D020000780008A0FF@mail.emea.novell.com> (raw)
In-Reply-To: <558D08FE.8010402@citrix.com>

>>> On 26.06.15 at 10:10, <andrew.cooper3@citrix.com> wrote:
> On 26/06/2015 07:22, Jan Beulich wrote:
>>>>> On 25.06.15 at 18:22, <andrew.cooper3@citrix.com> wrote:
>>> After recent consideration, I am still not sure if we want to support
>>> SMAP in 32bit PV guests or not.  The trapping of stac/clac would be a
>>> high overhead, although the guest could modify EFLAGS.AC itself using popf.
>> If it technically works (which it looks like it does) I see no reason
>> leaving the decision to guests.
> 
> True.  For now, I will leave SMAP/SMEP unexposed and leave the CPUID
> side of things to my levelling work.

In which case there's no point assuming an "aware" guest - with the
CPUID flag unexposed, writes to CR4.SMAP are simply invalid.

Jan

  reply	other threads:[~2015-06-26  8:50 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-24 16:31 [PATCH 0/8] [RFC] SMAP handling improvements for 32bit PV guests on Andrew Cooper
2015-06-24 16:31 ` [PATCH 1/8] common/vsprintf: Special-case DOMID_IDLE handling for %pv Andrew Cooper
2015-06-24 16:31 ` [PATCH 2/8] x86/traps: Avoid using current too early on boot Andrew Cooper
2015-06-24 16:31 ` [PATCH 3/8] x86/setup: Initialise CR4 before creating idle_vcpu[0] Andrew Cooper
2015-06-24 16:31 ` [PATCH 4/8] xen/x86: Clean up CR4 definitions Andrew Cooper
2015-06-24 16:31 ` [PATCH 5/8] xen/x86: Drop PSE from XEN_MINIMAL_CR4 Andrew Cooper
2015-06-24 16:31 ` [PATCH 6/8] xen/x86: Calculate PV CR4 masks at boot Andrew Cooper
2015-06-25 13:08   ` Jan Beulich
2015-06-25 13:31     ` Andrew Cooper
2015-06-25 13:40       ` Jan Beulich
2015-06-25 13:43         ` Andrew Cooper
2015-06-24 16:31 ` [PATCH 7/8] xen/x86: Rework CR4 handling for PV guests Andrew Cooper
2015-06-25 14:41   ` Jan Beulich
2015-06-25 16:22     ` Andrew Cooper
2015-06-26  6:22       ` Jan Beulich
2015-06-26  8:10         ` Andrew Cooper
2015-06-26  8:50           ` Jan Beulich [this message]
2015-06-24 16:31 ` [PATCH 8/8] xen/x86: Additional SMAP modes to work around buggy 32bit " Andrew Cooper
2015-06-25 11:18   ` David Vrabel
2015-06-25 11:53     ` Andrew Cooper
2015-06-25 15:12   ` Jan Beulich
2015-06-25 16:31     ` Andrew Cooper
2015-06-26  6:33   ` Jan Beulich

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