Re: [PATCH v3 02/11] x86/kexec: Add extra pointers totransition page table PGD, PUD, PMD and PTE
From: Jan Beulich
Date: Mon Jan 07 2013 - 08:05:04 EST
>>> On 07.01.13 at 13:52, Daniel Kiper <daniel.kiper@xxxxxxxxxx> wrote:
> On Mon, Jan 07, 2013 at 09:48:20AM +0000, Jan Beulich wrote:
>> >>> On 04.01.13 at 18:25, Daniel Kiper <daniel.kiper@xxxxxxxxxx> wrote:
>> > Right, so where is virtual mapping of control page established?
>> > I could not find relevant code in SLES kernel which does that.
>> In the hypervisor (xen/arch/x86/machine_kexec.c:machine_kexec_load()).
>> xen/arch/x86/machine_kexec.c:machine_kexec() then simply uses
> This (xen/arch/x86/machine_kexec.c:machine_kexec_load()) maps relevant
> page (allocated earlier by dom0) in hypervisor fixmap area. However,
> it does not make relevant mapping in transition page table which
> leads to crash when %cr3 is switched from Xen page table to
> transition page table.
That indeed could explain _random_ failures - the fixmap entries
get created with _PAGE_GLOBAL set, i.e. don't get flushed with
the CR3 write unless CR4.PGE is clear.
And I don't see how your allocation of intermediate page tables
would help: You wouldn't know where the mapping of the control
page lives until you're actually in the early relocate_kernel code.
Or was it that what distinguishes your cloned code from the
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/