Re: [Xen-devel] [v7][PATCH 07/16] hvmloader/e820: construct guest e820 table

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

> I think I would say:
>
> --
> Now use the hypervisor-supplied memory map to build our final e820 table:
> * Add regions for BIOS ranges and other special mappings not in the
> hypervisor map
> * Add in the hypervisor regions
> * Adjust the lowmem and highmem regions if we've had to relocate
> memory (adding a highmem region if necessary)
> * Sort all the ranges so that they appear in memory order.
> --
I'll update this and thanks a lot.

> > CC: Keir Fraser <keir@xxxxxxx>
> > CC: Jan Beulich <jbeulich@xxxxxxxx>
> > CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> > ---
[snip]

> > +    /* Low RAM goes here. Reserve space for special pages. */
> > +    BUG_ON(low_mem_end < (2u << 20));
> Won't this BUG if the guest was actually given less than 2GiB of RAM?
2u << 20 = 0x200000, so this is 2M, not 2G :)

> > +
> > +    /*
> > +     * We may need to adjust real lowmem end since we may
> > +     * populate RAM to get enough MMIO previously.
> > +     */
[snip]

> > +
> > +    /*
> > +     * And then we also need to adjust highmem.
> > +     */
> > +    if ( add_high_mem )
> > +    {
> > +        for ( i = 0; i < memory_map.nr_map; i++ )
> > +        {
> > +            if ( e820[i].type == E820_RAM &&
> > +                 e820[i].addr > (1ull << 32))
> > +                e820[i].size += add_high_mem;
> > +        }
> > +    }
> What if there was originally no high memory, but resizing the pci hole
> meant we had to create a high memory region?
You're right. We need to consider this case.

Thanks
Tiejun


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