Re: [PATCH] xen/vpci: fix memory type in guest_mem_bar_read()

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

On Tue, Dec 10, 2024 at 11:25:44AM -0500, Stewart Hildebrand wrote:
> Currently, if bar->type is anything other than VPCI_BAR_MEM32, the
> memory type bits get set to PCI_BASE_ADDRESS_MEM_TYPE_64 in the returned
> value. This leads to the wrong memory type for, e.g. VPCI_BAR_EMPTY.
> Only set PCI_BASE_ADDRESS_MEM_TYPE_64 when the bar type is
> VPCI_BAR_MEM64_LO.

I'm confused, VPCI_BAR_EMPTY shouldn't use guest_mem_bar_read() in the
first place, as its read handler should be vpci_read_val() instead.

Is there something I'm missing from init_header()?

        if ( size == 0 )
        {
            bars[i].type = VPCI_BAR_EMPTY;

            if ( !is_hwdom )
            {
                rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL,
                                       reg, 4, (void *)0);
                if ( rc )
                    goto fail;
            }

            continue;
        }

AFAICT guest_mem_bar_read() should only handle BAR types that are
either VPCI_BAR_MEM32, VPCI_BAR_MEM64_HI or VPCI_BAR_MEM64_LO, and
that seems to be correctly handled?

Thanks, Roger.