Messages in this thread Patch in this message | | | Date | Fri, 30 Nov 2012 11:26:47 -0800 | From | tip-bot for Vincent Palatin <> | Subject | [tip:x86/urgent] x86, fpu: Avoid FPU lazy restore after suspend |
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Commit-ID: c9370d1039848a813a63c3fd44b6e4833a78246a Gitweb: http://git.kernel.org/tip/c9370d1039848a813a63c3fd44b6e4833a78246a Author: Vincent Palatin <vpalatin@chromium.org> AuthorDate: Fri, 30 Nov 2012 10:52:03 -0800 Committer: H. Peter Anvin <hpa@linux.intel.com> CommitDate: Fri, 30 Nov 2012 10:58:14 -0800
x86, fpu: Avoid FPU lazy restore after suspend
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> Link: http://lkml.kernel.org/r/1354301523-5252-2-git-send-email-vpalatin@chromium.org Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> --- arch/x86/kernel/smpboot.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c80a33b..7610c58 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -68,6 +68,8 @@ #include <asm/mwait.h> #include <asm/apic.h> #include <asm/io_apic.h> +#include <asm/i387.h> +#include <asm/fpu-internal.h> #include <asm/setup.h> #include <asm/uv/uv.h> #include <linux/mc146818rtc.h> @@ -1230,6 +1232,9 @@ int native_cpu_disable(void) clear_local_APIC(); cpu_disable_common(); + + /* the FPU context will be lost, nobody owns it */ + this_cpu_write(fpu_owner_task, NULL); return 0; }
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