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

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

On 12/10/24 11:37, Roger Pau Monné wrote:
> 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?

Ah, you're right, sorry. I pulled this patch out of another series that
I'm working on, but failed to realize that guest_mem_bar_read shouldn't
be used for VPCI_BAR_EMPTY. Please disregard.