This is a note to let you know that I've just added the patch titled
Revert "x86/speculation: Simplify indirect_branch_prediction_barrier()"
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-x86-speculation-simplify-indirect_branch_prediction_barrier.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f208820a321f9b23d77d7eed89945d862d62a3ed Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
Date: Sat, 10 Feb 2018 23:39:23 +0000
Subject: Revert "x86/speculation: Simplify indirect_branch_prediction_barrier()"
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
commit f208820a321f9b23d77d7eed89945d862d62a3ed upstream.
This reverts commit 64e16720ea0879f8ab4547e3b9758936d483909b.
We cannot call C functions like that, without marking all the
call-clobbered registers as, well, clobbered. We might have got away
with it for now because the __ibp_barrier() function was *fairly*
unlikely to actually use any other registers. But no. Just no.
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: arjan.van.de.ven@xxxxxxxxx
Cc: dave.hansen@xxxxxxxxx
Cc: jmattson@xxxxxxxxxx
Cc: karahmed@xxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: pbonzini@xxxxxxxxxx
Cc: rkrcmar@xxxxxxxxxx
Cc: sironi@xxxxxxxxx
Link: http://lkml.kernel.org/r/1518305967-31356-3-git-send-email-dwmw@xxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/nospec-branch.h | 13 +++++++++----
arch/x86/include/asm/processor.h | 3 ---
arch/x86/kernel/cpu/bugs.c | 6 ------
3 files changed, 9 insertions(+), 13 deletions(-)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -164,10 +164,15 @@ static inline void vmexit_fill_RSB(void)
static inline void indirect_branch_prediction_barrier(void)
{
- alternative_input("",
- "call __ibp_barrier",
- X86_FEATURE_USE_IBPB,
- ASM_NO_INPUT_CLOBBER("eax", "ecx", "edx", "memory"));
+ asm volatile(ALTERNATIVE("",
+ "movl %[msr], %%ecx\n\t"
+ "movl %[val], %%eax\n\t"
+ "movl $0, %%edx\n\t"
+ "wrmsr",
+ X86_FEATURE_USE_IBPB)
+ : : [msr] "i" (MSR_IA32_PRED_CMD),
+ [val] "i" (PRED_CMD_IBPB)
+ : "eax", "ecx", "edx", "memory");
}
#endif /* __ASSEMBLY__ */
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -968,7 +968,4 @@ bool xen_set_default_idle(void);
void stop_this_cpu(void *dummy);
void df_debug(struct pt_regs *regs, long error_code);
-
-void __ibp_barrier(void);
-
#endif /* _ASM_X86_PROCESSOR_H */
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -337,9 +337,3 @@ ssize_t cpu_show_spectre_v2(struct devic
spectre_v2_module_string());
}
#endif
-
-void __ibp_barrier(void)
-{
- __wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0);
-}
-EXPORT_SYMBOL_GPL(__ibp_barrier);
Patches currently in stable-queue which might be from dwmw@xxxxxxxxxxxx are
queue-4.14/kvm-nvmx-set-the-cpu_based_use_msr_bitmaps-if-we-have-a-valid-l02-msr-bitmap.patch
queue-4.14/x86-nvmx-properly-set-spec_ctrl-and-pred_cmd-before-merging-msrs.patch
queue-4.14/x86-speculation-update-speculation-control-microcode-blacklist.patch
queue-4.14/x86-speculation-correct-speculation-control-microcode-blacklist-again.patch
queue-4.14/kvm-x86-reduce-retpoline-performance-impact-in-slot_handle_level_range-by-always-inlining-iterator-helper-methods.patch
queue-4.14/x86-speculation-clean-up-various-spectre-related-details.patch
queue-4.14/revert-x86-speculation-simplify-indirect_branch_prediction_barrier.patch