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Re: [PATCH for-4.17] Revert "x86/HVM: also dump stacks from show_execution_state()"
- To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- Date: Fri, 4 Nov 2022 14:58:33 +0000
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- Thread-topic: [PATCH for-4.17] Revert "x86/HVM: also dump stacks from show_execution_state()"
On 04/11/2022 14:43, Roger Pau Monne wrote:
> This reverts commit adb715db698bc8ec3b88c24eb88b21e9da5b6c07.
>
> The dumping of stacks for HVM guests is problematic, since it requires
> taking the p2m lock in order to walk the guest page tables and the
> p2m.
>
> The suggested solution to the issue is to introduce and use a lockless
> p2m walker, that relies on being executed with interrupts disabled in
> order to prevent any p2m pages from being freed while doing the
> walk.
>
> Note that modifications of p2m entries are already done atomically in
> order to prevent the hardware walker from seeing partially updated
> values.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, as agreed on the
x86 maintainers call.
~Andrew
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