Re: [Xen-devel] 答复: xen does not support the 8G large bar

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.08.16 at 05:18, <visen.gao@xxxxxxxxxx> wrote:
> Hi Jan,
> Thanks for your reply.
> Qemu-xen seems that has problem for support 8G large Bar.
> I think this patch is not perfect: 
> https://xenbits.xen.org/gitweb/?p=qemu-xen.git;a=commitdiff;h=aabc8530c7ba2b 
> e89e21463f051056ad7c255e6e
> Because I found upper 32bit bar of 8G large bar was not register.
> xen_pt_config_init.c:456  xen_pt_bar_reg_write
> 
> case XEN_PT_BAR_FLAG_UPPER:
>         bar_emu_mask = XEN_PT_BAR_ALLF;
>         bar_ro_mask = r_size ? r_size - 1 : 0;
>         break;
> r_size is always 0. So, bar_sz_upper is always 0xffffffff, regardless of 
> whether 64 bit BAR size is larger than 4G.

Depending on how qemu sets things up, the issue may simply be on
of wrong types being used: r->size is of type pcibus_t (which I
sincerely hope is a 64-bit type), yet r_size is uint32_t. But then
again r->size being pcibus_t suggests that d->io_regions[] fields
for the upper halves of 64-bit BARs may not get populated at all
(in which case a possible fix would likely be more involved). I'm not
a qemu expert, so I can't easily tell.

Jan


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