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

["Gaofeng (GaoFeng, Euler)" <visen.gao@xxxxxxxxxx>]

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=aabc8530c7ba2be89e21463f051056ad7c255e6e
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.
With Konrad 's help , I find a patch at qemu-xen-trad about sorppurt BAR size 
is larger than 4G, I will analyze this patch and see if it helps to me.

Feng

-----邮件原件-----
发件人: Jan Beulich [mailto:JBeulich@xxxxxxxx] 
发送时间: 2016年8月11日 17:35
收件人: Gaofeng (GaoFeng, Euler)
抄送: george.dunlap@xxxxxxxxxxxxx; Fanhenglong; Hanweidong (Randy); Lianxueguo 
(Albert); Huangpeng (Peter); xen-devel@xxxxxxxxxxxxx
主题: Re: [Xen-devel] xen does not support the 8G large bar

>>> On 11.08.16 at 05:30, <visen.gao@xxxxxxxxxx> wrote:
> According to the analysis hvmloader code, find a problem:
> 
> if (is_64bar) {
>                 bar_data_upper = pci_readl(devfn, bar_reg + 4);
>                 pci_writel(devfn, bar_reg + 4, ~0);
>                 bar_sz_upper = pci_readl(devfn, bar_reg + 4);
>                 pci_writel(devfn, bar_reg + 4, bar_data_upper);
>                 bar_sz = (bar_sz_upper << 32) | bar_sz;
>             }
>             bar_sz &= ~(bar_sz - 1);
> 
> read from the pci device, bar_sz_upper is 0xffffffff, if the bar size 
> is 8G, the bar_sz_upper should be 0xfffffffe.

But that doesn't indicate a problem with hvmloader. Instead that tells you that 
qemu isn't behaving correctly. First thing for you to do is probably to try a 
newer qemu, or otherwise see whether you can figure why qemu sends back 
0xffffffff in this case (perhaps by adding a little bit of logging to the 
respective code).

Jan

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