Re: Limitations for Running Xen on KVM Arm64

[Julien Grall <julien@xxxxxxx>]

On 05/11/2025 13:39, haseeb.ashraf@xxxxxxxxxxx wrote:
> Hi,
Hi Haseeb,

> I have sent out a patch using IPAS2E1IS. The R version RIPAS2E1IS would only be 
> helpful if we have to invalidate more than one page at a time and this is not 
> possible unless a batch version of hypercall is implemented because otherwise 
> there is only one page removed per hypercall.
I have only briefly look at your patch. You have the following loop:

    /* Invalidate stage-2 TLB entries by IPA range */
    for ( i = 0; i < page_count; i++ ) {
        flush_guest_tlb_one_s2(ipa);
        ipa += 1UL << PAGE_SHIFT;
    }

With RIPAS2E1IS, you would be able to replace this loop with a single 
instruction. This may not have any value in your setup because you are 
unmaping 4KB at the time. But there are other hypercalls (such as 
XENMEM_decrease_reservation) where you can remove larger mapping.
So I think there are some values to use the range version. Although, I 
would be fine if this is not handled in your current patch.
> Thanks again for your great suggestions. Please review my patch, you should've 
> received an email.
I will add it in my list of reviews.

Cheers,

--
Julien Grall