Re: [Xen-devel] [RFC 0/8] xen/arm: acpi: Support SPIs routing

[Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>]

Hi Julien,

Sure, I'll test this patchset on Qualcomm Technologies QDF2XXX platform and 
update results.


On 06/07/2016 11:48 AM, Julien Grall wrote:
> Hi all,
>
> Currently, Xen does not route SPIs to DOM0 when ACPI is inuse after
> the functionality has been reverted in Xen 4.7 by commit 909bd14.
>
> In the previous approach, the SPIs was routed when DOM0 was writing into
> ISENABLER. However, this has resulted to deadlock (see more details in [1])
> as soon as the IRQ was enabled by DOM0.
>
> We have multiple solutions to route the IRQ:
>  1) Rework route_irq_to_guest to avoid the deadlock
>  2) Route and enable the IRQ outside of the emulation of ISENABLER
>  3) Remove the dependency on the IRQ type in the routing function
>  and route all the unused IRQs during domain building
>  4) Add a new hypercall to let DOM0 routing the IRQ
>
> I think that 1) and 2) are not resilient because route_irq_to_guest may fail
> and there is no way to report this error to the guest (except by killing it).
>
> Furthermore, in solution 2) enabling the interrupt would need to be defer
> until the routing has been done. This would require a lot of code duplication.
>
> Which leave solution 3) and 4). The solution 4) requires to introduce a new
> (or re-use one) stable hypercall. I am not sure why we ruled out this
> solution when we reviewed the ACPI design document.
>
> This patch series is implementing the 3rd solution which defer the IRQ
> type configuration for DOM0 IRQ when ACPI is inuse. However, this will
> slightly increase the memory usage of Xen (54KB).
>
> I am happy to consider any other solutions.
>
> I only tested briefly this patch series, Shanker can you give a try on
> your hardware?
>
> A branch with all the patches can be found here:
>
> git://xenbits.xen.org/people/julieng/xen-unstable.git branch 
> irq-routing-acpi-rfc
>
> Yours sincerely,
>
> [1] http://lists.xenproject.org/archives/html/xen-devel/2016-05/msg02633.html
>
> Julien Grall (8):
>   xen/arm: gic: Consolidate the IRQ affinity set in a single place
>   xen/arm: gic: Do not configure affinity for guest IRQ during routing
>   xen/arm: gic: split set_irq_properties
>   xen/arm: gic: set_type: Pass the type in parameter rather than in
>     desc->arch.type
>   xen/arm: gic: Document how gic_set_irq_type should be called
>   Revert "xen/arm: warn the user that we cannot route SPIs to Dom0 on
>     ACPI"
>   xen/arm: Allow DOM0 to set the irq type when ACPI is inuse
>   xen/arm: acpi: route all unused IRQs to DOM0
>
>  xen/arch/arm/domain_build.c | 19 ++++++++-----------
>  xen/arch/arm/gic-v2.c       | 28 +++++++++++++---------------
>  xen/arch/arm/gic-v3.c       | 22 ++++++++++------------
>  xen/arch/arm/gic.c          | 34 ++++++++++++++++++++++------------
>  xen/arch/arm/irq.c          | 14 +++++++++++++-
>  xen/arch/arm/vgic.c         | 34 ++++++++++++++++++++--------------
>  xen/include/asm-arm/gic.h   | 11 +++++++----
>  xen/include/asm-arm/irq.h   |  6 ++++++
>  8 files changed, 99 insertions(+), 69 deletions(-)
>

-- 
Shanker Donthineni
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux 
Foundation Collaborative Project


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