[Qemu-devel] 答复: using which notification for guest about GHES error

[gengdongjiu]

Hi Igor,
  Thanks for your reply.

> On Mon, 16 Oct 2017 14:10:05 +0800
> gengdongjiu <address@hidden> wrote:
> 
> > Hi Igor/Michael,
> >    I am very sorry to disturb you again.
> > Now we use Qemu to create APEI table and record CPER for guest, After
> > QEMU recorded a asynchronous CPER error, we needs to notify guest using 
> > interrupt or Polled notification.
> > For the asynchronous error. I think using GPIO-signaled notification may be 
> > better in the Qemu, and also which is suggested by APEI spec.
> > James worried that old guest OS may not support GPIO or GSIV notification 
> > for GHES, because GPIO or GSIV notification is supported in OS
> since about kernel version 4.10.
> 
> How APEI support is fairly new on ARM (kernel), isn't it still in state of 
> development?
> Do we really care about old guests in this case?

How APEI support is new feature on ARM64, because it mainly exists in ARMv8.2 
architecture.
May be we cannot very care about old guest.
Because even we use the old notification(such as polled notification), the 
guest OS may still not have APEI support, so it is still not useless.
I checked the patches history, the APEI support is only enabled recent. 

As we can see APEI/GHES is only enabled in "2017-06-21 12:30:44 -0500", the old 
version OS even does not have APEI support.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v4.14-rc5&id=c792e5e644fd8cd38b963fd3b38f6bf57c530966

James, what do you think about it?

> 
> We'd like to stick to ACPI spec as much as possible and also to
> http://infocenter.arm.com/help/topic/com.arm.doc.den0044b/DEN0044B_Server_Base_Boot_Requirements.pdf
> which mandates GPIO in platform (QEMU)
> "
> 4.5 Hardware Requirements Imposed on the Platform by ACPI ...
> Platforms compliant with this specification must provide the following 
> GPIO-Signaled platform events:
> ...
> "
> 
> > and suggested using Polled notification. About above two notifications, do 
> > you think which is better? and could you give us some
> suggestion? thanks.
> how polling is supposed to be implemented in QEMU?
> 
> >
> >
> > Hi James,
> >   Below is APEI spec, From the spec, it suggested using GPIO interrupt or 
> > GPIO-signaled events in ARM64 [1]. If using Polled notification
> for GHES, I do not sure whether it is reasonable.
> > In the Qemu, X86 does not using Polled notification. it mainly use
> > SCI. Until now, I do not found there is peopled using Polled notification 
> > in qemu. if implemented polled notification, I do not know how
> much work effort need to do. Now I have already implemented the GPIO-Signal 
> notification using GPIO pin.
> >
> >
> > [1]
> > HW-reduced ACPI platforms signal the error using a GPIO interrupt or
> > another interrupt declared under a generic event device (Section 5.6.9). In 
> > the case of GPIO-signaled events, an _AEI object lists the
> appropriate GPIO pin, while for Interrupt-signaled events a _CRS object is 
> used to list the interrupt:
> >     • The OSPM evaluates the control method associated with this event as 
> > indicated in Section 5.6.5.3 and Section 5.6.9.3.
> >     • OSPM responds to this notification by checking the error status block 
> > of all generic error sources with the GPIO-Signal notification or
> Interrupt-signaled notification types to identify the
> >       source reporting the error.
> >