Re: [Xen-devel] [PATCH] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries

[Ingo Molnar <mingo@xxxxxxxxxx>]

* Alex Thorlton <athorlton@xxxxxxx> wrote:

> On systems with sufficiently large e820 tables, and several IOAPICs, it
> is possible for the XENMEM_machine_memory_map callback (and its
> counterpart, XENMEM_memory_map) to attempt to return an e820 table with
> more than 128 entries.  This callback adds entries to the BIOS-provided
> e820 table to account for IOAPIC registers, which, on sufficiently large
> systems, can result in an e820 table that is too large to copy back into
> xen_e820_map.
> 
> This change simply increases the size of xen_e820_map to E820_X_MAX to
> ensure that there is enough room to store the entire e820 map returned
> from this callback.

This means:

 #ifdef CONFIG_EFI
 #include <linux/numa.h>
 #define E820_X_MAX (E820MAX + 3 * MAX_NUMNODES)
 #else   /* ! CONFIG_EFI */
 #define E820_X_MAX E820MAX
 #endif

It's a bit weird to key it off of CONFIG_EFI - why isn't it unconditional?

But I have no objections to the principle if it fixes a crash.

Thanks,

        Ingo

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