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Message-ID: <CAJcbSZG7ds+q76dHtzOkYtMkkTXWwG3e7MAxKJi0=SmdmqA6tA@mail.gmail.com>
Date: Tue, 14 Mar 2017 14:20:19 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: Pavel Machek <pavel@....cz>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
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Subject: Re: [PATCH v7 3/3] x86: Make the GDT remapping read-only on 64-bit
On Tue, Mar 14, 2017 at 2:04 PM, Pavel Machek <pavel@....cz> wrote:
> On Tue 2017-03-14 10:05:08, Thomas Garnier wrote:
>> This patch makes the GDT remapped pages read-only to prevent corruption.
>> This change is done only on 64-bit.
>>
>> The native_load_tr_desc function was adapted to correctly handle a
>> read-only GDT. The LTR instruction always writes to the GDT TSS entry.
>> This generates a page fault if the GDT is read-only. This change checks
>> if the current GDT is a remap and swap GDTs as needed. This function was
>> tested by booting multiple machines and checking hibernation works
>> properly.
>>
>> KVM SVM and VMX were adapted to use the writeable GDT. On VMX, the
>> per-cpu variable was removed for functions to fetch the original GDT.
>> Instead of reloading the previous GDT, VMX will reload the fixmap GDT as
>> expected. For testing, VMs were started and restored on multiple
>> configurations.
>>
>> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
>
> Can we get the same change for 32-bit, too? Growing differences
> between 32 and 64 bit are a bit of a problem...
> Pavel
It was discussed on previous versions that 32-bit read-only support
would create issues that why it was favor for 64-bit only right now.
>
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
Thomas
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