Re: [PATCH] tools/init-xenstore-domain: fix memory map for PVH stubdom

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Fri, Jun 24, 2022 at 11:28:06AM +0200, Juergen Gross wrote:
> In case of maxmem != memsize the E820 map of the PVH stubdom is wrong,
> as it is missing the RAM above memsize.
> 
> Additionally the MMIO area should only cover the HVM special pages.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>  tools/helpers/init-xenstore-domain.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/helpers/init-xenstore-domain.c 
> b/tools/helpers/init-xenstore-domain.c
> index b4f3c65a8a..dad8e43c42 100644
> --- a/tools/helpers/init-xenstore-domain.c
> +++ b/tools/helpers/init-xenstore-domain.c
> @@ -157,21 +158,24 @@ static int build(xc_interface *xch)
>          config.flags |= XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap;
>          config.arch.emulation_flags = XEN_X86_EMU_LAPIC;
>          dom->target_pages = mem_size >> XC_PAGE_SHIFT;
> -        dom->mmio_size = GB(4) - LAPIC_BASE_ADDRESS;
> +        dom->mmio_size = X86_HVM_NR_SPECIAL_PAGES << XC_PAGE_SHIFT;
>          dom->lowmem_end = (mem_size > LAPIC_BASE_ADDRESS) ?
>                            LAPIC_BASE_ADDRESS : mem_size;
>          dom->highmem_end = (mem_size > LAPIC_BASE_ADDRESS) ?
>                             GB(4) + mem_size - LAPIC_BASE_ADDRESS : 0;
> -        dom->mmio_start = LAPIC_BASE_ADDRESS;
> +        dom->mmio_start = (X86_HVM_END_SPECIAL_REGION -
> +                           X86_HVM_NR_SPECIAL_PAGES) << XC_PAGE_SHIFT;
>          dom->max_vcpus = 1;
>          e820[0].addr = 0;
> -        e820[0].size = dom->lowmem_end;
> +        e820[0].size = (max_size > LAPIC_BASE_ADDRESS) ?
> +                       LAPIC_BASE_ADDRESS : max_size;
>          e820[0].type = E820_RAM;
> -        e820[1].addr = LAPIC_BASE_ADDRESS;
> +        e820[1].addr = dom->mmio_start;


So, it isn't expected to have an entry covering the LAPIC addresses,
right? I guess not as seen in df1ca1dfe20.

But based on that same commit info, shouldn't the LAPIC address part of
`dom->mmio_start, dom->mmio_size`? (I don't know how dom->mmio_start is
used, yet, but maybe it's used by Xen or xen libraries to avoid
allocations in the wrong places)

Thanks,

-- 
Anthony PERARD