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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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.

Jan


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