Re: [PATCH v5 13/14] xen/arm: account IO handlers for emulated PCI MSI-X

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Nov 25, 2021 at 01:02:50PM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> 
> At the moment, we always allocate an extra 16 slots for IO handlers
> (see MAX_IO_HANDLER). So while adding IO trap handlers for the emulated
> MSI-X registers we need to explicitly tell that we have additional IO
> handlers, so those are accounted.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

LGTM, just one comment below. This will require an Ack from the Arm
guys.

> ---
> Cc: Julien Grall <julien@xxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> ---
> This actually moved here from the part 2 of the prep work for PCI
> passthrough on Arm as it seems to be the proper place for it.
> 
> New in v5
> ---
>  xen/arch/arm/vpci.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
> index 3d134f42d07e..902f8491e030 100644
> --- a/xen/arch/arm/vpci.c
> +++ b/xen/arch/arm/vpci.c
> @@ -134,6 +134,8 @@ static int vpci_get_num_handlers_cb(struct domain *d,
>  
>  unsigned int domain_vpci_get_num_mmio_handlers(struct domain *d)
>  {
> +    unsigned int count;
> +
>      if ( !has_vpci(d) )
>          return 0;
>  
> @@ -145,7 +147,18 @@ unsigned int domain_vpci_get_num_mmio_handlers(struct 
> domain *d)
>      }
>  
>      /* For a single emulated host bridge's configuration space. */
> -    return 1;
> +    count = 1;
> +
> +#ifdef CONFIG_HAS_PCI_MSI
> +    /*
> +     * There's a single MSI-X MMIO handler that deals with both PBA
> +     * and MSI-X tables per each PCI device being passed through.
> +     * Maximum number of emulated virtual devices is VPCI_MAX_VIRT_DEV.
> +     */
> +    count += VPCI_MAX_VIRT_DEV;

You could also use IS_ENABLED(CONFIG_HAS_PCI_MSI) since
VPCI_MAX_VIRT_DEV is defined unconditionally.

Thanks, Roger.