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Re: [Xen-devel] [PATCH] x86: store cr4 during suspend/resume
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Tue, 10 Dec 2019 09:59:17 +0000
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- Cc: Wei Liu <wl@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- Delivery-date: Tue, 10 Dec 2019 09:59:23 +0000
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On 09/12/2019 18:06, Roger Pau Monne wrote:
> Currently cr4 is not cached before suspension, and mmu_cr4_features is
> used in order to restore the expected cr4 value. This is correct so
> far because the tasklet that executes the suspend/resume code is
> running in the idle vCPU context.
>
> In order to make the code less fragile, explicitly save the current
> cr4 value before suspension, so that it can be restored afterwards.
> This ensures that the cr4 value cached in the cpu_info doesn't get out
> of sync after resume from suspension.
>
> Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Why? There is nothing fragile here. Suspend/resume is always in idle
context and loads of other logic already depends on this.
I've been slowly stripping out redundant saved state like this.
~Andrew
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