Re: [Xen-devel] Problem with IOMEM and domain reboot

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

Ian, Wei,

could you please take a look at the below?

Thank you,

Oleksandr


On 12/20/2017 06:27 PM, Oleksandr Andrushchenko wrote:
> Hi, all!
>
> While trying to reboot a domain which has iomem configured
> (we are passing through some devices), I found an issue,
> that after domain reboot those iomem's are incorrectly re-mapped,
> e.g. for the configuration snippet below fe960 -> 0.
>
> Part of the domain config I use:
> iomem=[
>     "0xfd010,1@0xfd000",
>     "fe960,8",
> ]
>
> During domain creation:
> libxl_create.c:210:libxl__domain_build_info_setdefault: iomem gfn 
> fd000 start fd010
> libxl_create.c:210:libxl__domain_build_info_setdefault: iomem gfn 
> ffffffffffffffff start fe960
> which means that for fe960 initial value was set to LIBXL_INVALID_GFN
> and then on domain configuration, 
> tools/libxl/libxl_create.c:libxl__domain_build_info_setdefault:
>     for (i = 0 ; i < b_info->num_iomem; i++)
>         if (b_info->iomem[i].gfn == LIBXL_INVALID_GFN)
>             b_info->iomem[i].gfn = b_info->iomem[i].start;
>
> made that GFN for fe960 to be set to the correct value.
>
> But during domain reboot I see that 
> tools/xl/xl_vmcontrol.c:reload_domain_config
> tries to replicate configuration from the original domain config
> being rebooted, but that leads to iomem's GFN to be set to 0 (if 
> configured
> in form [IOMEM_START,NUM_PAGES], but for [IOMEM_START,NUM_PAGES[@GFN] 
> it is ok):
> iomem gfn fd000 start fd010
> iomem gfn 0 start fe960
>
> Thus, further domain restart procedure leads to invalid mapping, e.g. 
> fe960 -> 0.
> I created a patch which allowed me to reboot the domain, but I would love
> to hear comments on what would be the proper fix.
>
> Thank you,
> Oleksandr

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