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authorLinus Torvalds <torvalds@linux-foundation.org>2023-05-03 09:38:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-05-03 10:37:22 -0700
commit1dbc0a9515fdf1f0b9d6c9b1954a347c94e5f5f9 (patch)
treed7c7e10a98b14677622dd61309bf81cd57193841 /arch/x86/hyperv
parentb9bd9f605c4a6f04a83e6640a7d1d6dda80f17ca (diff)
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x86: mm: remove 'sign' games from LAM untagged_addr*() macros
The intent of the sign games was to not modify kernel addresses when untagging them. However, that had two issues: (a) it didn't actually work as intended, since the mask was calculated as 'addr >> 63' on an _unsigned_ address. So instead of getting a mask of all ones for kernel addresses, you just got '1'. (b) untagging a kernel address isn't actually a valid operation anyway. Now, (a) had originally been true for both 'untagged_addr()' and the remote version of it, but had accidentally been fixed for the regular version of untagged_addr() by commit e0bddc19ba95 ("x86/mm: Reduce untagged_addr() overhead for systems without LAM"). That one rewrote the shift to be part of the alternative asm code, and in the process changed the unsigned shift into a signed 'sar' instruction. And while it is true that we don't want to turn what looks like a kernel address into a user address by masking off the high bit, that doesn't need these sign masking games - all it needs is that the mm context 'untag_mask' value has the high bit set. Which it always does. So simplify the code by just removing the superfluous (and in the case of untagged_addr_remote(), still buggy) sign bit games in the address masking. Acked-by: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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