Re: [PATCH v21 1/2] arm/vpci: mask off upper bits in vPCI read mmio handler

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 8 May 2025, Stewart Hildebrand wrote:
> On Arm, we expect read handlers to have the bits above the access size
> zeroed. vPCI read handlers may return all 1s. Mask off the bits above
> the access size.
> 
> Fixes: 9a5e22b64266 ("xen/arm: check read handler behavior")
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  xen/arch/arm/vpci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
> index b63a356bb4a8..3a3ff5d0812c 100644
> --- a/xen/arch/arm/vpci.c
> +++ b/xen/arch/arm/vpci.c
> @@ -37,7 +37,7 @@ static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
>      if ( vpci_ecam_read(sbdf, ECAM_REG_OFFSET(info->gpa),
>                          1U << info->dabt.size, &data) )
>      {
> -        *r = data;
> +        *r = data & invalid;
>          return 1;
>      }
>  
> -- 
> 2.49.0
>