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Re: [PATCH v10 10/13] xen/arm64: Save/restore CPU context across SYSTEM_SUSPEND
- To: Mykola Kvach <xakep.amatop@xxxxxxxxx>
- From: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- Date: Mon, 1 Jun 2026 17:58:45 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Mykola Kvach <mykola_kvach@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
- Delivery-date: Mon, 01 Jun 2026 17:59:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v10 10/13] xen/arm64: Save/restore CPU context across SYSTEM_SUSPEND
Hi Mykola,
> On 21 May 2026, at 18:45, Mykola Kvach <xakep.amatop@xxxxxxxxx> wrote:
>
> From: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
>
> On wakeup from PSCI SYSTEM_SUSPEND, Xen re-enters EL2 with the MMU and
> data cache disabled. The resume path must first switch back to Xen's
> runtime page tables before it can access the saved CPU context using
> virtual addresses.
>
> Add an arm64 hyp_resume trampoline that reuses enable_secondary_cpu_mm()
> to enable the data cache and MMU, switch to init_ttbr, and resume in the
> runtime virtual mapping. The trampoline then restores the saved CPU
> general-purpose and system-control register context.
>
> prepare_resume_ctx() must be invoked just before the PSCI system suspend
> call is issued to the platform firmware. It saves the current CPU context
> and returns a non-zero value so that the caller enters the physical
> SYSTEM_SUSPEND call.
>
> On resume, hyp_resume restores the saved context, including the saved link
> register. Control therefore returns to the place where prepare_resume_ctx()
> was called. To avoid re-entering the suspend path, the restored path sees
> prepare_resume_ctx() return zero.
>
> The assembly save/restore code uses offsets generated by asm-offsets.c
> from struct resume_cpu_context, keeping the assembly memory accesses in
> sync with the C structure layout.
>
> Support for ARM32 is not implemented. Instead, compilation fails with a
> build-time error if suspend is enabled for ARM32.
>
> Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xxxxxxxxxx>
> Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
> Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> ---
Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Cheers,
Luca
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