Messages in this thread | | | Date | Sun, 10 May 2020 10:46:25 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v3 09/10] x86/fpu/xstate: Preserve supervisor states for slow path of __fpu__restore_sig() |
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On Sat, Mar 28, 2020 at 09:43:06AM -0700, Yu-cheng Yu wrote: > The signal return code is responsible for taking an XSAVE buffer present > in user memory and loading it into the hardware registers. This > operation only affects user XSAVE state and never affects supervisor state. > > The fast path through this code simply points XRSTOR directly at the > user buffer. However, due to page faults, this XRSTOR can fail. If it ^^^^^^^^^^^^^^^^^^
"However, since user memory is not guaranteed to be always mapped, ... "
> fails, the signal return code falls back to a slow path which can > tolerate page faults. > > That slow path copies the xfeatures one by one out of the user buffer > into the task's fpu state area. However, by being in a context where it > can handle page faults, the code can also schedule. That exposes us to ^^ Pls use passive voice in your commit message: no "we" or "I", etc, and describe your changes in imperative mood.
Fix this in all your commit messages pls.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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