Hi Ayan,
On 13/10/2022 17:05, Ayan Kumar Halder wrote:
On 13/10/2022 16:38, Julien Grall wrote:
Hi,
Hi Julien,
On 13/10/2022 16:13, Ayan Kumar Halder wrote:
On 13/10/2022 15:47, Julien Grall wrote:
.Thus, the guest need to invoke sys_read32() twice (GICR_TYPER and
GICR_TYPER+4).
I don't understand how you came to this conclusion with what you wrote.
Sorry for confusion. I was trying to explain that the code does not
handle 32 bit access of GICR_TYPER on arm32.
If we had implemented vreg_reg64_extract(), then Zephyr would still
need to issue two 32-bit read because Xen doesn't emulate 'ldrd'.
Yes. So what we need here is not the implementation of
vreg_reg64_extract() for GICR_TYPER.
Why not? Your GICR_TYPER is a 64-bit and the helper is the right way
to hide whether the low/high 32-bit are accessed.
When Zephyr issues 32 bit reads for GICR_TYPER for GICR_TYPER + 4, it
traps to Xen two times.
So, my understanding is that Xen needs to read two 32 bit values.
We can modify the vreg_reg64_extract() so that it can return the lower
32 bits in one case and upper 32 bits in the second case.
Is this what you are suggesting ?
Well... The helper is already doing that. It was introduced to support
32-bit guest using GICv3 on 64-bit Xen.
Cheers,
--
Julien Grall
