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authorHugh Dickins <hughd@google.com>2017-09-24 16:59:49 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-05 15:44:25 +0100
commite345dcc9481543edf4a0a5df4c4c2f9597b0a997 (patch)
treeed084a4c22b576f9ed6b3980b0e383b1ac09f38f /Documentation
parent500943e57db8d3e298e98f595f835c5b613e843b (diff)
kaiser: add "nokaiser" boot option, using ALTERNATIVE
Added "nokaiser" boot option: an early param like "noinvpcid". Most places now check int kaiser_enabled (#defined 0 when not CONFIG_KAISER) instead of #ifdef CONFIG_KAISER; but entry_64.S and entry_64_compat.S are using the ALTERNATIVE technique, which patches in the preferred instructions at runtime. That technique is tied to x86 cpu features, so X86_FEATURE_KAISER is fabricated. Prior to "nokaiser", Kaiser #defined _PAGE_GLOBAL 0: revert that, but be careful with both _PAGE_GLOBAL and CR4.PGE: setting them when nokaiser like when !CONFIG_KAISER, but not setting either when kaiser - neither matters on its own, but it's hard to be sure that _PAGE_GLOBAL won't get set in some obscure corner, or something add PGE into CR4. By omitting _PAGE_GLOBAL from __supported_pte_mask when kaiser_enabled, all page table setup which uses pte_pfn() masks it out of the ptes. It's slightly shameful that the same declaration versus definition of kaiser_enabled appears in not one, not two, but in three header files (asm/kaiser.h, asm/pgtable.h, asm/tlbflush.h). I felt safer that way, than with #including any of those in any of the others; and did not feel it worth an asm/kaiser_enabled.h - kernel/cpu/common.c includes them all, so we shall hear about it if they get out of synch. Cleanups while in the area: removed the silly #ifdef CONFIG_KAISER from kaiser.c; removed the unused native_get_normal_pgd(); removed the spurious reg clutter from SWITCH_*_CR3 macro stubs; corrected some comments. But more interestingly, set CR4.PSE in secondary_startup_64: the manual is clear that it does not matter whether it's 0 or 1 when 4-level-pts are enabled, but I was distracted to find cr4 different on BSP and auxiliaries - BSP alone was adding PSE, in probe_page_size_mask(). Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt2
1 files changed, 2 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b4a83a490212..67d4f67f56ba 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2523,6 +2523,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
nojitter [IA-64] Disables jitter checking for ITC timers.
+ nokaiser [X86-64] Disable KAISER isolation of kernel from user.
+
no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page