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From: "Jan Beulich" <JBeulich@suse.com>
To: Feng Wu <feng.wu@intel.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Keir Fraser <keir@xen.org>,
	xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 2/4] x86: suppress SMAP and SMEP while running 32-bit PV guest code
Date: Wed, 09 Mar 2016 07:07:06 -0700	[thread overview]
Message-ID: <56E03C1A02000078000DADDD@prv-mh.provo.novell.com> (raw)
In-Reply-To: <E959C4978C3B6342920538CF579893F00C369E91@SHSMSX104.ccr.corp.intel.com>

>>> On 09.03.16 at 09:09, <feng.wu@intel.com> wrote:
>> From: Jan Beulich [mailto:JBeulich@suse.com]
>> Sent: Friday, March 4, 2016 7:28 PM
>> @@ -1471,7 +1475,10 @@ void __init noreturn __start_xen(unsigne
>>       * copy_from_user().
>>       */
>>      if ( cpu_has_smap )
>> +    {
>> +        cr4_smep_smap_mask &= ~X86_CR4_SMAP;
> 
> You change ' cr4_smep_smap_mask ' here ...
> 
>>          write_cr4(read_cr4() & ~X86_CR4_SMAP);
>> +    }
>> 
>>      printk("%sNX (Execute Disable) protection %sactive\n",
>>             cpu_has_nx ? XENLOG_INFO : XENLOG_WARNING "Warning: ",
>> @@ -1488,7 +1495,10 @@ void __init noreturn __start_xen(unsigne
>>          panic("Could not set up DOM0 guest OS");
>> 
>>      if ( cpu_has_smap )
>> +    {
>>          write_cr4(read_cr4() | X86_CR4_SMAP);
>> +        cr4_smep_smap_mask |= X86_CR4_SMAP;
> 
> ... and here. I am wonder whether it is because Domain 0 can actually start
> running between the two place? Or I don't think the changes in the above
> two places is needed. right?

They very definitely needed, to avoid hitting the BUG in
cr4_pv32_restore (cr4_smep_smap_restore in this patch
version) in every interrupt that occurs while Dom0 is being
constructed.

Jan


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  parent reply	other threads:[~2016-03-09 14:07 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-04 11:08 [PATCH 0/4] x86: accommodate 32-bit PV guests with SMAP/SMEP handling Jan Beulich
2016-03-04 11:27 ` [PATCH 1/4] x86/alternatives: correct near branch check Jan Beulich
2016-03-07 15:43   ` Andrew Cooper
2016-03-07 15:56     ` Jan Beulich
2016-03-07 16:11       ` Andrew Cooper
2016-03-07 16:21         ` Jan Beulich
2016-03-08 17:33           ` Andrew Cooper
2016-03-04 11:27 ` [PATCH 2/4] x86: suppress SMAP and SMEP while running 32-bit PV guest code Jan Beulich
2016-03-07 16:59   ` Andrew Cooper
2016-03-08  7:57     ` Jan Beulich
2016-03-09  8:09       ` Wu, Feng
2016-03-09 14:09         ` Jan Beulich
2016-03-09 11:19       ` Andrew Cooper
2016-03-09 14:28         ` Jan Beulich
2016-03-09  8:09   ` Wu, Feng
2016-03-09 10:45     ` Andrew Cooper
2016-03-09 12:27       ` Wu, Feng
2016-03-09 12:33         ` Andrew Cooper
2016-03-09 12:36           ` Jan Beulich
2016-03-09 12:54             ` Wu, Feng
2016-03-09 13:35             ` Wu, Feng
2016-03-09 13:42               ` Andrew Cooper
2016-03-09 14:03       ` Jan Beulich
2016-03-09 14:07     ` Jan Beulich [this message]
2016-03-04 11:28 ` [PATCH 3/4] x86: use optimal NOPs to fill the SMAP/SMEP placeholders Jan Beulich
2016-03-07 17:43   ` Andrew Cooper
2016-03-08  8:02     ` Jan Beulich
2016-03-04 11:29 ` [PATCH 4/4] x86: use 32-bit loads for 32-bit PV guest state reload Jan Beulich
2016-03-07 17:45   ` Andrew Cooper
2016-03-10  9:44 ` [PATCH v2 0/3] x86: accommodate 32-bit PV guests with SMEP/SMAP handling Jan Beulich
2016-03-10  9:53   ` [PATCH v2 1/3] x86: suppress SMEP and SMAP while running 32-bit PV guest code Jan Beulich
2016-05-13 15:48     ` Andrew Cooper
2016-03-10  9:54   ` [PATCH v2 2/3] x86: use optimal NOPs to fill the SMEP/SMAP placeholders Jan Beulich
2016-05-13 15:49     ` Andrew Cooper
2016-03-10  9:55   ` [PATCH v2 3/3] x86: use 32-bit loads for 32-bit PV guest state reload Jan Beulich
     [not found]   ` <56E9A0DB02000078000DD54C@prv-mh.provo.novell.com>
2016-03-17  7:50     ` [PATCH v3 0/4] x86: accommodate 32-bit PV guests with SMEP/SMAP handling Jan Beulich
2016-03-17  8:02       ` [PATCH v3 1/4] x86: move cached CR4 value to struct cpu_info Jan Beulich
2016-03-17 16:20         ` Andrew Cooper
2016-03-17  8:03       ` [PATCH v3 2/4] x86: suppress SMEP and SMAP while running 32-bit PV guest code Jan Beulich
2016-03-25 18:01         ` Konrad Rzeszutek Wilk
2016-03-29  6:55           ` Jan Beulich
2016-05-13 15:58         ` Andrew Cooper
2016-03-17  8:03       ` [PATCH v3 3/4] x86: use optimal NOPs to fill the SMEP/SMAP placeholders Jan Beulich
2016-05-13 15:57         ` Andrew Cooper
2016-05-13 16:06           ` Jan Beulich
2016-05-13 16:09             ` Andrew Cooper
2016-03-17  8:04       ` [PATCH v3 4/4] x86: use 32-bit loads for 32-bit PV guest state reload Jan Beulich
2016-03-25 18:02         ` Konrad Rzeszutek Wilk
2016-03-17 16:14       ` [PATCH v3 5/4] x86: reduce code size of struct cpu_info member accesses Jan Beulich
2016-03-25 18:47         ` Konrad Rzeszutek Wilk
2016-03-29  6:59           ` Jan Beulich
2016-03-30 14:28             ` Konrad Rzeszutek Wilk
2016-03-30 14:42               ` Jan Beulich
2016-05-13 16:11         ` Andrew Cooper
2016-05-03 13:58       ` Ping: [PATCH v3 2/4] x86: suppress SMEP and SMAP while running 32-bit PV guest code Jan Beulich
2016-05-03 14:10         ` Andrew Cooper
2016-05-03 14:25           ` Jan Beulich
2016-05-04 10:03             ` Andrew Cooper
2016-05-04 13:35               ` Jan Beulich
2016-05-04  3:07         ` Wu, Feng
2016-05-13 15:21         ` Wei Liu
2016-05-13 15:30           ` Jan Beulich
2016-05-13 15:33             ` Wei Liu
2016-05-13 17:02       ` [PATCH v3 0/4] x86: accommodate 32-bit PV guests with SMEP/SMAP handling Wei Liu
2016-05-13 17:21         ` Andrew Cooper
2016-06-21  6:19       ` Wu, Feng
2016-06-21  7:17         ` Jan Beulich

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