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
*before*
they made it into the architecture (there seem to be a 6 month delay
between
the architecture being sampled and the documentation being released).
M.
--
Jazz is not dead. It just smells funny...
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