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authorPaul Burton <paul.burton@mips.com>2018-08-30 21:01:21 +0300
committerPaul Burton <paul.burton@mips.com>2018-08-31 20:07:21 +0300
commit0f02cfbc3d9e413d450d8d0fd660077c23f67eff (patch)
tree37d29a9eef33764f7974c5863a9f7a7fcdac7d9b /Kconfig
parent5b394b2ddf0347bef56e50c69a58773c94343ff3 (diff)
downloadlinux-0f02cfbc3d9e413d450d8d0fd660077c23f67eff.tar.xz
MIPS: VDSO: Match data page cache colouring when D$ aliases
When a system suffers from dcache aliasing a user program may observe stale VDSO data from an aliased cache line. Notably this can break the expectation that clock_gettime(CLOCK_MONOTONIC, ...) is, as its name suggests, monotonic. In order to ensure that users observe updates to the VDSO data page as intended, align the user mappings of the VDSO data page such that their cache colouring matches that of the virtual address range which the kernel will use to update the data page - typically its unmapped address within kseg0. This ensures that we don't introduce aliasing cache lines for the VDSO data page, and therefore that userland will observe updates without requiring cache invalidation. Signed-off-by: Paul Burton <paul.burton@mips.com> Reported-by: Hauke Mehrtens <hauke@hauke-m.de> Reported-by: Rene Nielsen <rene.nielsen@microsemi.com> Reported-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Fixes: ebb5e78cc634 ("MIPS: Initial implementation of a VDSO") Patchwork: https://patchwork.linux-mips.org/patch/20344/ Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Tested-by: Hauke Mehrtens <hauke@hauke-m.de> Cc: James Hogan <jhogan@kernel.org> Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # v4.4+
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