Re: [PATCH 1/2] KVM: arm64: Hide FEAT_LS64_ACCDATA from guests

["Arnd Bergmann" <arnd@arndb.de>]

On Thu, Nov 12, 2026, at 19:07, Siddharth Chintamaneni wrote:
> On Tue, Oct 27, 2026 at 02:48:29PM +0100, Arnd Bergmann wrote:
>> On Sat, Oct 24, 2026, at 09:14, Fuad Tabba wrote:
>> > On a host that runs at EL1 (nVHE or hVHE), this also requires
>> > __init_el2_fgt to set nACCDATA_EL1 in HFGRTR_EL2 and HFGWTR_EL2, and
>> > __init_el2_hcrx to set HCRX_EL2.EnAS0. Without them, the ACCDATA_EL1
>> > access traps to EL2 and the hypervisor panics, and so does ST64BV0
>> > once SCTLR_EL1.EnAS0 is set. Happy to write those and the KVM change
>> > once you're ready to post this.
>>
>> Thanks for the offer, that part is definitely not my area.
>
> We are preparing to post the Microsoft Smart Data Accelerator (SDA) VF
> dmaengine driver for Microsoft Cobalt SoCs, which uses IOMMU SVA with
> direct EL0 ST64BV0 portal submissions carrying the process PASID in
> ACCDATA_EL1.
>
> Now that Fuad's KVM guest FEAT_LS64_ACCDATA series is queued, are you
> planning to post the host ST64BV0 SVA + EL2/KVM patches as a standalone
> series soon?

Yes, sorry for the delay on my side, I'll try to get it to you ASAP.

For my understanding of your requirements:

- Is that hardware using an SMMUv3 or a different type of IOMMU?
- Do you have userspace calling ST64BV0 on the host, guest or possibly both?

> Either way, we have Cobalt hardware with FEAT_LS64_ACCDATA available and
> would be happy to test your patches on silicon, or help put together and
> carry any remaining pieces alongside our driver series if you prefer.

Sounds good, thanks!

    Arnd