| Date | Tue, 8 Dec 2015 19:48:19 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 30/34] x86, fpu: allow setting of XSAVE state |
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On Thu, 3 Dec 2015, Dave Hansen wrote:
> > From: Dave Hansen <dave.hansen@linux.intel.com> > > We want to modify the Protection Key rights inside the kernel, so > we need to change PKRU's contents. But, if we do a plain > 'wrpkru', when we return to userspace we might do an XRSTOR and > wipe out the kernel's 'wrpkru'. So, we need to go after PKRU in > the xsave buffer. > > We do this by: > 1. Ensuring that we have the XSAVE registers (fpregs) in the > kernel FPU buffer (fpstate) > 2. Looking up the location of a given state in the buffer > 3. Filling in the stat > 4. Ensuring that the hardware knows that state is present there > (basically that the 'init optimization' is not in place). > 5. Copying the newly-modified state back to the registers if > necessary. > > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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