Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage | Date | Tue, 08 Jun 2021 14:27:54 +0200 |
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On Tue, Jun 08 2021 at 13:17, Thomas Gleixner wrote: > On Mon, Jun 07 2021 at 09:38, Dave Hansen wrote: >> On 6/7/21 7:08 AM, Thomas Gleixner wrote: >>>> By the way, are you talking specifically about the _error_ paths where >>>> the kernel is unable to XRSTOR the signal XSAVE buffer for some reason, >>>> and tries to apply either init_fpu or the hardware init state instead? >>> >>> 1) Successful XRSTOR from user if the PKRU feature bit in the >>> sigframe xsave.header.xfeatures is cleared. Both fast and slow path. >> >> It seems like the suggestion here is to inject 'init_pkru_value' in all >> cases where the kernel would be injecting the hardware init value. I >> don't think we should go that far. >> >> If a signal handler sets xsave.header.xfeatures[PKRU]=0, I can't imagine >> any other intent than wanting the hardware init value. > > Fine. But PKRU=0 is broken today... > > T1 in user space > wrpkru(0)
It's actually not wrpkru(0), but a XRSTOR with the xsave.header.xfeatures[PKRU] bit cleared. But the rest is the same...
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