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authorLinus Torvalds <torvalds@linux-foundation.org>2020-08-23 11:21:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-23 11:21:16 -0700
commit550c2129d93d5eb198835ac83c05ef672e8c491c (patch)
tree922fe5453bb6d9c4e0c8091d2d3149089706f93d /security
parentcea05c192b07b82a770816fc9d06031403cea164 (diff)
parent6a3ea3e68b8a8a26c4aaac03432ed92269c9a14e (diff)
Merge tag 'x86-urgent-2020-08-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fix from Thomas Gleixner: "A single fix for x86 which removes the RDPID usage from the paranoid entry path and unconditionally uses LSL to retrieve the CPU number. RDPID depends on MSR_TSX_AUX. KVM has an optmization to avoid expensive MRS read/writes on VMENTER/EXIT. It caches the MSR values and restores them either when leaving the run loop, on preemption or when going out to user space. MSR_TSX_AUX is part of that lazy MSR set, so after writing the guest value and before the lazy restore any exception using the paranoid entry will read the guest value and use it as CPU number to retrieve the GSBASE value for the current CPU when FSGSBASE is enabled. As RDPID is only used in that particular entry path, there is no reason to burden VMENTER/EXIT with two extra MSR writes. Remove the RDPID optimization, which is not even backed by numbers from the paranoid entry path instead" * tag 'x86-urgent-2020-08-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/entry/64: Do not use RDPID in paranoid entry to accomodate KVM
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