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Re: [Xen-devel] [PATCH for-4.11] x86/suspend: Fix restoration of guest state across S3/S4

>>> On 21.06.18 at 10:37, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 21/06/18 16:29, Jan Beulich wrote:
>>>>> On 20.06.18 at 12:12, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> The call to freeze_domains() in enter_state() guarentees that we are
>>> running in idle context for the duration of S3/S4.
>>> In restore_rest_processor_state(), the stts() is problematic as it
>>> unilaterally sets %cr0.ts even in fully_eager FPU context.  It also fails to
>>> account for the non-lazy xsave state.  Luckily, these are both latent bugs, 
>>> as
>>> the FPU state is corrected by the subsequent context switch away from the 
>>> idle
>>> vcpu.
>>> Another aspect is that the !is_idle_vcpu(curr) paths in
>>> restore_rest_processor_state() are actually dead code, and removing
>>> these highlights that the segment saving logic is also unused.
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> For 4.12:
>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>> As mentioned elsewhere (and despite having seen Jürgen's R-a-b) I'm not
>> convinced this is an appropriate change to make for 4.11, considering how
>> late in the process we are. If we want to consider this instead of my much
>> smaller suggested change, then we will want to have someone actively
>> using S3 test this thoroughly. Don't forget that whatever we do on 4.11 to
>> address the regression will also want backporting.
> Yes - considering how this patch ended up, I withdraw the 4.11 part of
> it.  An earlier development version had a functional fix for lazy
> segment restoration which is why I thought it was going to be properly
> needed for 4.11
> As this is straight deletion, it can wait until 4.12

Thanks. With the moved (in the EFI patch) assertion, mine can actually be
further simplified. I'll submit this in a minute.


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