Subject: Re: [PATCH v7 0/7] Add support for FEAT_{LS64, LS64_V} and related tests

From: Oliver Upton <[email-masked]>
Date: Fri, 7 Nov 2025 10:57:54 -0800

On Fri, Nov 07, 2025 at 03:21:20PM +0800, Zhou Wang wrote:
> Armv8.7 introduces single-copy atomic 64-byte loads and stores
> instructions and its variants named under FEAT_{LS64, LS64_V}.
> Add support for Armv8.7 FEAT_{LS64, LS64_V}:
> - Add identifying and enabling in the cpufeature list
> - Expose the support of these features to userspace through HWCAP3 and cpuinfo
> - Add related hwcap test
> - Handle the trap of unsupported memory (normal/uncacheable) access in a VM
> 
> A real scenario for this feature is that the userspace driver can make use of
> this to implement direct WQE (workqueue entry) - a mechanism to fill WQE
> directly into the hardware.
> 
> Picked Marc's 2 patches form [1] for handling the LS64 trap in a VM on emulated
> MMIO and the introduce of KVM_EXIT_ARM_LDST64B.

Besides the ordering issue the KVM bits of this look fine to me. If
these patches go through the kvmarm tree then I'd be happy to fix that
up when applying.

Will / Catalin, any preferences on which tree this goes in? If you guys
take it:

Acked-by: Oliver Upton <[email-masked]>

Thanks,
Oliver