Hi Marc,
On 2020/3/20 17:09, Marc Zyngier wrote:
Hi Zenghui,
On 2020-03-20 04:38, Zenghui Yu wrote:
Hi Marc,
On 2020/3/19 23:21, Marc Zyngier wrote:
With GICv4.1, you can introspect the HW state for SGIs. You can also
look at the vLPI state by peeking at the virtual pending table, but
you'd need to unmap the VPE first,
Out of curiosity, could you please point me to the "unmap the VPE"
requirement in the v4.1 spec? I'd like to have a look.
Sure. See IHI0069F, 5.3.19 (VMAPP GICv4.1), "Caching of virtual LPI data
structures", and the bit that says:
"A VMAPP with {V,Alloc}=={0,1} cleans and invalidates any caching of the
Virtual Pending Table and Virtual Configuration Table associated with the
vPEID held in the GIC"
which is what was crucially missing from the GICv4.0 spec (it doesn't say
when the GIC is done writing to memory).
OK. Thanks for the pointer!
Side note: it'd be good to know what the rules are for your own GICv4
implementations, so that we can at least make sure the current code is
safe.
As far as I know, there will be some clean and invalidate operations
when v4.0 VPENDBASER.Valid gets programmed. But not sure about behaviors
on VMAPP (unmap), it may be a totally v4.1 stuff. I'll have a talk with
our SOC team.
But how can the current code be unsafe? Is anywhere in the current code
will peek/poke the vpt (whilst GIC continues writing things into it)?
Thanks,
Zenghui
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