Messages in this thread | | | Date | Fri, 30 Nov 2012 10:57:05 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86, fpu: avoid FPU lazy restore after suspend |
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On 11/30/2012 10:52 AM, Vincent Palatin wrote: > When a cpu enters S3 state, the FPU state is lost. > After resuming for S3, if we try to lazy restore the FPU for a process running > on the same CPU, this will result in a corrupted FPU context. > > We can just invalidate the "fpu_owner_task", so nobody will try to > lazy restore a state which no longer exists in the hardware. > > Tested with a 64-bit kernel on a 4-core Ivybridge CPU with eagerfpu=off, > by doing thousands of suspend/resume cycles with 4 processes doing FPU > operations running. Without the patch, a process is killed after a > few hundreds cycles by a SIGFPE. > > The issue seems to exist since 3.4 (after the FPU lazy restore was actually implemented), > to apply the change to 3.4, "this_cpu_write" needs to be replaced by percpu_write. > > Cc: Duncan Laurie <dlaurie@chromium.org> > Cc: Olof Johansson <olofj@chromium.org> > Cc: <stable@kernel.org> [v3.4+] # for 3.4 need to replace this_cpu_write by percpu_write > Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
Ouch! Thank you for catching this!
-hpa
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