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authorLinus Torvalds <torvalds@linux-foundation.org>2024-03-11 16:15:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2024-03-11 16:15:43 -0700
commit86833aec447939a886a13bbdbdf21c9628c5c8c5 (patch)
tree012fcbe7a89ae6fe1b3fee89f037051dffd3637c /block
parent720c857907530e6cdc86c9bc1102ea6b372fbfb6 (diff)
parentbb998361999e79bc87dae1ebe0f5bf317f632585 (diff)
Merge tag 'x86-entry-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 entry update from Thomas Gleixner: "A single update for the x86 entry code: The current CR3 handling for kernel page table isolation in the paranoid return paths which are relevant for #NMI, #MCE, #VC, #DB and #DF is unconditionally writing CR3 with the value retrieved on exception entry. In the vast majority of cases when returning to the kernel this is a pointless exercise because CR3 was not modified on exception entry. The only situation where this is necessary is when the exception interrupts a entry from user before switching to kernel CR3 or interrupts an exit to user after switching back to user CR3. As CR3 writes can be expensive on some systems this becomes measurable overhead with high frequency #NMIs such as perf. Avoid this overhead by checking the CR3 value, which was saved on entry, and write it back to CR3 only when it is a user CR3" * tag 'x86-entry-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/entry: Avoid redundant CR3 write on paranoid returns
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