Re: [PATCH 0/2] KVM: arm64: Fix and test MMIO sign-extending loads

[Oliver Upton]

On Mon, Jun 22, 2026 at 08:06:59PM +0100, Fuad Tabba wrote:
> Hi folks,
> 
> A sign-extending load (LDRSB/LDRSH/LDRSW) from emulated MMIO returns a
> zero-extended value rather than the sign-extended one the architecture
> requires; vcpu_data_host_to_guest() strips the sign bits when it masks
> the data to the access width.
> 
> If my git archeology is right, the masking dates to 2014 (b30070862edbd,
> big-endian support) and has been wrong ever since, but sign-extending
> loads from device memory are rare enough that nobody hit it. Patch 1
> fixes it; patch 2 adds a selftest so it doesn't regress.
> 
> Cheers,
> /fuad
> 
> Fuad Tabba (2):
>   KVM: arm64: Fix sign-extension of MMIO loads
>   KVM: arm64: selftests: Add MMIO sign-extending load test

For the oddball guest :)

Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx>

Thanks,
Oliver