[lkml]   [2020]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v5 01/23] irqchip/gic-v3: Use SGIs without active state if offered
On 2020-03-12 09:28, Marc Zyngier wrote:
> Hi Zenghui,
> On 2020-03-12 06:30, Zenghui Yu wrote:
>> Hi Marc,
>> On 2020/3/5 4:33, Marc Zyngier wrote:
>>> To allow the direct injection of SGIs into a guest, the GICv4.1
>>> architecture has to sacrifice the Active state so that SGIs look
>>> a lot like LPIs (they are injected by the same mechanism).
>>> In order not to break existing software, the architecture gives
>>> offers guests OSs the choice: SGIs with or without an active
>>> state. It is the hypervisors duty to honor the guest's choice.
>>> For this, the architecture offers a discovery bit indicating whether
>>> the GIC supports GICv4.1 SGIs (GICD_TYPER2.nASSGIcap), and another
>>> bit indicating whether the guest wants Active-less SGIs or not
>>> (controlled by GICD_CTLR.nASSGIreq).
>> I still can't find the description of these two bits in IHI0069F.
>> Are they actually architected and will be available in the future
>> version of the spec? I want to confirm it again since this has a
>> great impact on the KVM code, any pointers?
> Damn. The bits *are* in the engineering spec version 19 (unfortunately
> not a public document, but I believe you should have access to it).
> If the bits have effectively been removed from the spec, I'll drop the
> GICv4.1 code from the 5.7 queue until we find a way to achieve the same
> level of support.
> I've emailed people inside ARM to find out.

I've now had written confirmation that the bits are still there.

It is just that the current revision of the documentation was cut
they made it into the architecture (there seem to be a 6 month delay
the architecture being sampled and the documentation being released).

Jazz is not dead. It just smells funny...

 \ /
  Last update: 2020-03-12 13:05    [W:0.692 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site