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xen-devel
Re: [Xen-devel] Re: Balloon driver crash
On 06/03/2010 03:38 PM, Dave McCracken wrote:
> On Thursday, June 03, 2010, Ian Campbell wrote:
>
>>> This seems to be about line 343 of drivers/xen/balloon.c in the
>>> subroutine decrease_reservation which is
>>>
>>> for (j = 0; j < balloon_npages; j++, lpfn++, mfn++) {
>>> if ((discontig_frame_list[j] =
>>> pfn_to_mfn(lpfn))
>>>
>>> != mfn)
>>>
>>> discontig_free = 1;
>>>
>>> set_phys_to_machine(lpfn, INVALID_P2M_ENTRY);
>>>
>>> /* here */ if (!PageHighMem(page)) {
>>>
>>> ret = HYPERVISOR_update_va_mapping(
>>> (unsigned long)__va(lpfn <<
>>>
>>> PAGE_SHIFT),
>>>
>>> __pte_ma(0), 0);
>>> BUG_ON(ret);
>>> }
>>> }
>>>
>>>
>>> >From what I can tell page is meaningless in this context as it is just
>>>
>>> a temporary variable used in the previous loop, so I would
>>> guess that PageHighMem should be checking something else, or page should
>>> be set somewhere eg. at a guess page=pfn_to_page(lpfn);
>>>
>> That would be my guess also. CCing Dave McCracken who looks to have
>> introduced this code in 0e898d5e "Add hugepage support to balloon
>> driver"
>>
> Yes, that is definitely an error. The offending line should be
>
> if (!PageHighMem(pfn_to_page(lpfn))) {
>
Actually it looks like this was fixed on the xen/hugepage-balloon a long
time ago, but I guess that branch wasn't merged across to xen/next
because it was based on xen/master and so awkward to merge into the
.32-based and later branches.
I need to check how the current hugepage support has made it into the
.32 based tree, assuming it has. It will take a bit of git archeology.
J
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