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 ?
- Ayan
Zephyr will issue two 32 bit read access for GICR_TYPER and
(GICR_TYPER + 4). So Xen needs to emulate 32 bit read for GICR_TYPER
and GICR_TYPER + 4.
So, we will need to modify the Xen code as follows :-
|#ifdef AARCH32 case VREG32(GICR_TYPER_L32) : { read and return lower
32 bits of GICR_TYPER return 1; } case VREG32(GICR_TYPER_H32) : {
read and return the upper 32 bits of GICR_TYPER return 1; } #else /*
For AARCH64 */ case VREG64(GICR_TYPER): { do as existing; } #endif
Let me know if this looks sane. I can then submit a single patch to
add support for this. |
This is a bit difficult to read. So I looked at your answer on the
Zephyr thread.
You will end up to duplicate code for emulating TYPER and there are
quite a few other use of vreg_reg64_extract() in the code.
So I am afraid this is not an option for me. If you implement
vreg_reg64_* then you will not need to implement.
I would be open to other suggestion so long we don't end up with
duplication or any other kind of open-coding.
Cheers,
