Mark, and team,
Before going upstream (specifically to Greg), we would like your opinion
on the following issue:
PAGE_TABLE_ISOLATION feature - to mitigate meltdown - is not enabled by
default for i686 (X32) mainly because it depends on HIGHMEM and X86_PAE.
X86_PAE is NOT default on x86 32bit compilations and it gets only
automatically selected if HIGHMEM64G is set (which would justify its need).
With that, right now, all 32-bit kernels generated with default config
options are susceptible to meltdown vulnerability
(https://bugs.linaro.org/show_bug.cgi?id=4135).
We are thinking on enabling CONFIG_PAGE_TABLE_ISOLATION (w/
CONFIG_X86_PAE and CONFIG_HIGHMEM64G options) for our x86 32-bit builds,
but we aren't sure if we should ask upstream to consider the same, since
X86_PAE does not look like something that should be default.
What do you think ? Thanks for your inputs!
Rafael
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Rafael D. Tinoco
Linaro - Kernel Validation