Messages in this thread | | | Date | Wed, 10 Jul 2019 22:02:40 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86/asm: Move native_write_cr0/3() out of line |
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On Wed, Jul 10, 2019 at 09:42:46PM +0200, Thomas Gleixner wrote: > The pinning of sensitive CR0 and CR4 bits caused a boot crash when loading > the kvm_intel module on a kernel compiled with CONFIG_PARAVIRT=n. > > The reason is that the static key which controls the pinning is marked RO > after init. The kvm_intel module contains a CR4 write which requires to > update the static key entry list. That obviously does not work when the key > is in a RO section. > > With CONFIG_PARAVIRT enabled this does not happen because the CR4 write > uses the paravirt indirection and the actual write function is built in. > > As the key is intended to be immutable after init, move > native_write_cr0/3() out of line. > > While at it consolidate the update of the cr4 shadow variable and store the > value right away when the pinning is initialized on a booting CPU. No point > in reading it back 20 instructions later. This allows to confine the static > key and the pinning variable to cpu/common and allows to mark them static. > > Fixes: 8dbec27a242c ("x86/asm: Pin sensitive CR0 bits") > Fixes: 873d50d58f67 ("x86/asm: Pin sensitive CR4 bits") > Reported-by: Linus Torvalds <torvalds@linux-foundation.org> > Reported-by: Xi Ruoyao <xry111@mengyan1223.wang> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Tested-by: Xi Ruoyao <xry111@mengyan1223.wang>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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