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| author |   Thomas Gleixner <tglx@linutronix.de> | 2019-02-18 23:42:51 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-03-06 21:52:13 +0100 |
| commit | 04dcbdb8057827b043b3c71aa397c4c63e67d086 (patch) | |
| tree | ef837807f05eaf4ce6abe5d62b5ef5703931c3e5 /arch/x86/include/asm/nospec-branch.h | |
| parent | x86/speculation/mds: Add mds_clear_cpu_buffers() (diff) | |
| download | linux-dev-04dcbdb8057827b043b3c71aa397c4c63e67d086.tar.xz linux-dev-04dcbdb8057827b043b3c71aa397c4c63e67d086.zip | |
x86/speculation/mds: Clear CPU buffers on exit to user
Add a static key which controls the invocation of the CPU buffer clear
mechanism on exit to user space and add the call into
prepare_exit_to_usermode() and do_nmi() right before actually returning.
Add documentation which kernel to user space transition this covers and
explain why some corner cases are not mitigated.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Jon Masters <jcm@redhat.com>
Tested-by: Jon Masters <jcm@redhat.com>
Diffstat (limited to 'arch/x86/include/asm/nospec-branch.h')
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 67cb9b2082b1..65b747286d96 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -318,6 +318,8 @@ DECLARE_STATIC_KEY_FALSE(switch_to_cond_stibp); DECLARE_STATIC_KEY_FALSE(switch_mm_cond_ibpb); DECLARE_STATIC_KEY_FALSE(switch_mm_always_ibpb); +DECLARE_STATIC_KEY_FALSE(mds_user_clear); + #include <asm/segment.h> /** @@ -343,6 +345,17 @@ static inline void mds_clear_cpu_buffers(void) asm volatile("verw %[ds]" : : [ds] "m" (ds) : "cc"); } +/** + * mds_user_clear_cpu_buffers - Mitigation for MDS vulnerability + * + * Clear CPU buffers if the corresponding static key is enabled + */ +static inline void mds_user_clear_cpu_buffers(void) +{ + if (static_branch_likely(&mds_user_clear)) + mds_clear_cpu_buffers(); +} + #endif /* __ASSEMBLY__ */ /* |