On Saturday 21 March 2009, Jeremy Fitzhardinge wrote:
> Hi Len,
>
> I have a patch here ported from the linux2.6.18-xen tree to make host S3
> suspend work under Xen (attached).
>
> The salient part is this:
>
> --- a/drivers/acpi/acpica/hwsleep.c
> +++ b/drivers/acpi/acpica/hwsleep.c
> @@ -46,6 +46,9 @@
> #include "accommon.h"
> #include "actables.h"
>
> +#include <xen/acpi.h>
> +#include <asm/xen/hypervisor.h>
> +
> #define _COMPONENT ACPI_HARDWARE
> ACPI_MODULE_NAME("hwsleep")
>
> @@ -337,14 +340,19 @@ acpi_status asmlinkage acpi_enter_sleep_state(u8 sleep_state)
>
> ACPI_FLUSH_CPU_CACHE();
>
> - status = acpi_hw_register_write(ACPI_REGISTER_PM1A_CONTROL,
> - PM1Acontrol);
> - if (ACPI_FAILURE(status)) {
> - return_ACPI_STATUS(status);
> - }
> + if (!xen_pv_domain()) {
> + status = acpi_hw_register_write(ACPI_REGISTER_PM1A_CONTROL,
> + PM1Acontrol);
> + if (ACPI_FAILURE(status)) {
> + return_ACPI_STATUS(status);
> + }
> +
> + status = acpi_hw_register_write(ACPI_REGISTER_PM1B_CONTROL,
> + PM1Bcontrol);
> + } else
> + status = acpi_notify_hypervisor_state(sleep_state,
> + PM1Acontrol, PM1Bcontrol);
>
> - status = acpi_hw_register_write(ACPI_REGISTER_PM1B_CONTROL,
> - PM1Bcontrol);
> if (ACPI_FAILURE(status)) {
> return_ACPI_STATUS(status);
> }
>
>
> where acpi_notify_hypervisor_state() more or less maps directly onto a
> Xen hypercall, which in turn performs the corresponding acpi operation
> from within Xen.
>
> I'm guessing you won't find this patch appealing as-is because it sticks
> a great big if (xen) into an otherwise arch (and OS?) independent piece
> of code. In this particular instance, its fairly easy to envisage
> encapsulating these two register writes into their own function which
> architectures can override, which makes it fairly easy for me to put a
> Xen hook in somewhere on the arch/x86 side of the fence.
>
> But because Xen ends up doing the low-level cpu state save/restore,
> several other parts of the S3 suspend path can be skipped on the Linux
> side. I'm wondering if you have any thoughts about how that can be
> done, or if putting the Xen code in as-is is acceptable?
>
> (BTW, xen_pv_domain() expands to a constant 0 when Xen isn't enabled in
> the config, so the Xen-dependent bits will collapse down to nothing.
> But it is defined in asm/xen/hypervisor.h, which is only present on x86
> and ia64 architectures; on the other hand, believe those are the only
> architectures using acpi.)
Well, why don't you implement the platform suspend operations for Xen?
I guess you don't want ACPI _PTS to be executed during suspend as well.
Rafael
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