Re: [Xen-devel] [PATCH v2 00/45] New VGIC(-v2) implementation

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

Hi,

On 20/03/18 08:30, Julien Grall wrote:
> Hi,
> 
> On 03/15/2018 08:30 PM, Andre Przywara wrote:
>> tl;dr: Coarse changelog below, individual patches have changelogs as
>> well. git branch:
>> http://www.linux-arm.org/git?p=xen-ap.git;a=shortlog;h=refs/heads/vgic-new/v2
>>
>> git://linux-arm.org/xen-ap.git branch vgic-new/v2
>>
>> Another update, addressing the review comments. Nothing too
>> outstanding this
>> time, the most interesting changes include:
>> - removing the split-out preparatory patches, which are already merged
>> - changing the setting and clearing of _IRQ_INPROGRESS
>> - including Julien's LR access rework series
>> - restricting new level IRQ handling to the new VGIC
>> - fix multiple SGI handling (mimicing the recent Linux/KVM patch)
>> - ASSERTing that h/w IRQs stay connected to their virtual IRQs
>> - directly update h/w affinity, without taking the desc lock
>> - restrict 8K struct vcpu to new VGIC and ARM64
>> - use separate Makefile for vgic/ directory
>> - many minor changes to address whitespace issues and usage of unsigned,
>>    also extending comments
>>
>> A summarising changelog can be found below, each individual patch has
>> its own changelog as well.
>>
>> There are some things that have (still) not been covered yet:
>> - struct VCPU still allocates two pages on ARM64 when using the new
>> VGIC now.
>> We could try to look if we can allocate some parts of struct vcpu
>> instead of
>> embedding sub-structures into it.
>> - vGICv3 support is not implemented, but should be fairly
>> straight-forward to
>> add, as the design incorporated this already. Will look at this next.
>> - There is a possible DOS vector on the VCPU ap_list, which holds pending
>> vIRQs. A guest can make this list rather long, which forces the
>> hypervisor
>> to hold the list lock when iterating the list. This should be bounded by
>> the number of emulated vIRQs though, and there are ideas how to mitigate
>> this issue. Those fixes would be posted on top as fixes later.
>> - There is no ITS support, though the VGIC code itself is more ready
>> for that
>> than the old VGIC ever was. However due to differences between the Xen
>> and KVM architecture the ITS bits are not easy to port over to Xen.
>> - Do we need to call vgic_evtchn_irq_pending() in
>> local_event_needs_delivery_nomask()? The event channel IRQ should be
>> covered
>> by the VGIC already.
> 
> Thank you for summarising the open questions! I will log them on jira
> once the series is merged.

Good idea, thanks!

> Meanwhile, I have committed patches #1 - #8.

Many thanks for that! Only 37 to go ;-)
Will try to send a v3 later today.

Cheers,
Andre.

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