[PATCH 0/1] x86: work around X86-32 kernel failures on Intel Atom CPU

[Tim Gardner]

Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> *** HARDY LPIA ONLY ***
> 
> BugLink: https://bugs.launchpad.net/bugs/523112
> 
> This is a workaround to errata AAE44 as listed in
> http://download.intel.com/design/processor/specupdt/319536.pdf,
> page 33, namely: "Code Fetch May Occur to Incorrect Address
> After a Large Page is Split into 4-KB Byte Pages". This is the same
> as Errata AAH41 (Atom 3xx series) but named AAE44 for the Atom
> Z5xx series.
> 
> This fix is not totally bullet proof. There is still a possibility
> of a race between __set_pmd_pte and __flush_tlb_all() during which
> the other hyperthread could do a code fetch and get garbage. Hence
> this patch narrows the window for the race but does not completely
> prevent it.
> 
> This patch has been soak tested on an Atom Z530 for 2 hours. Without 
> this patch, the soak test can reproduce an oops within 5 minutes of
> testing.
> 
> Also boot tested on two Atom N270 netbooks and Intel 
> 
> 
> This patch is a backport of the upstream commit
> 211b3d03c7400f48a781977a50104c9d12f4e229, the original commit message
> was as follows:
> 
> Impact: work around boot crash
> 
> Work around Intel Atom erratum AAH41 (probabilistically) - it's triggering
> in the field.
> 
> Reported-by: Linus Torvalds <torvalds at linux-foundation.org>
> Tested-by: Kyle McMartin <kyle at redhat.com>
> Signed-off-by: Ingo Molnar <mingo at elte.hu>
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> 
> 
> Colin Ian King (1):
>   UBUNTU: x86: work around X86-32 kernel failures on Intel Atom CPU
> 
>  arch/x86/mm/pageattr_32.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> 

Acked-by Tim Gardner <tim.gardner at canonical.com>

-- 
Tim Gardner tim.gardner at canonical.com