Re: [PATCH v2] ARM: GICv3 ITS: flush caches for newly allocated ITT

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

On 9/22/23 18:27, Volodymyr Babchuk wrote:
> ITS manages Device Tables and Interrupt Translation Tables on its own,
> so generally we are not interested in maintaining any coherence with
> CPU's view of those memory regions, except one case: ITS requires that
> Interrupt Translation Tables should be initialized with
> zeroes. Existing code already does this, but it does not cleans
> caches afterwards. This means that ITS may see un-initialized ITT and
> CPU can overwrite portions of ITT later, when it finally decides to
> flush caches. Visible effect of this issue that there are not
> interrupts delivered from a device.
> 
> Fix this by calling clean_and_invalidate_dcache_va_range() for newly
> allocated ITT.
> 
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>

Tested-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>

> 
> ---
> 
> Changes since v1:
>  - Use clean_and_invalidate_dcache_va_range() instead of
>    clean_dcache_va_range()
>  - Do this unconditionally
>  - Do not rename  HOST_ITS_FLUSH_CMD_QUEUE into HOST_ITS_FLUSH_BUFFERS
> ---
>  xen/arch/arm/gic-v3-its.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/xen/arch/arm/gic-v3-its.c b/xen/arch/arm/gic-v3-its.c
> index 3aa4edda10..8afcd9783b 100644
> --- a/xen/arch/arm/gic-v3-its.c
> +++ b/xen/arch/arm/gic-v3-its.c
> @@ -685,6 +685,9 @@ int gicv3_its_map_guest_device(struct domain *d,
>      if ( !itt_addr )
>          goto out_unlock;
> 
> +    clean_and_invalidate_dcache_va_range(itt_addr,
> +                                         nr_events * hw_its->itte_size);
> +
>      dev = xzalloc(struct its_device);
>      if ( !dev )
>          goto out_unlock;
> --
> 2.42.0