Re: [PATCH v2 2/3] powerpc/fsl: Add barrier_nospec implementation for NXP PowerPC Book3E
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2018-07-03 07:26:06
Hi Diana, A few comments below ... Diana Craciun [off-list ref] writes:
Implement the barrier_nospec as a isync;sync instruction sequence. The implementation uses the infrastructure built for BOOK3S 64.
Do you have any details on why that sequence functions as an effective
barrier on your chips?
In a lot of places we have eg:
+#if defined(CONFIG_PPC_BOOK3S_64) || defined(CONFIG_PPC_FSL_BOOK3E)
Can you please add a Kconfig symbol to capture that. eg.
config PPC_NOSPEC
bool
default y
depends on PPC_BOOK3S_64 || PPC_FSL_BOOK3E
And then use that everywhere.
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diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h index f67b3f6..405d572 100644 --- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h@@ -86,6 +86,16 @@ do { \ // This also acts as a compiler barrier due to the memory clobber. #define barrier_nospec() asm (stringify_in_c(barrier_nospec_asm) ::: "memory") +#elif defined(CONFIG_PPC_FSL_BOOK3E) +/* + * Prevent the execution of subsequent instructions speculatively using a + * isync;sync instruction sequence. + */ +#define barrier_nospec_asm NOSPEC_BARRIER_FIXUP_SECTION; nop; nop + +// This also acts as a compiler barrier due to the memory clobber. +#define barrier_nospec() asm (stringify_in_c(barrier_nospec_asm) ::: "memory") + #else /* !CONFIG_PPC_BOOK3S_64 */ #define barrier_nospec_asm #define barrier_nospec()
If we have CONFIG_PPC_NOSPEC this can be done something like: #ifdef CONFIG_PPC_BOOK3S_64 #define NOSPEC_BARRIER_SLOT nop #elif defined(CONFIG_PPC_FSL_BOOK3E) #define NOSPEC_BARRIER_SLOT nop; nop #endif /* CONFIG_PPC_BOOK3S_64 */ #ifdef CONFIG_PPC_NOSPEC /* * Prevent execution of subsequent instructions until preceding branches have * been fully resolved and are no longer executing speculatively. */ #define barrier_nospec_asm NOSPEC_BARRIER_FIXUP_SECTION; NOSPEC_BARRIER_SLOT // This also acts as a compiler barrier due to the memory clobber. #define barrier_nospec() asm (stringify_in_c(barrier_nospec_asm) ::: "memory") #else #define barrier_nospec_asm #define barrier_nospec() #endif /* CONFIG_PPC_NOSPEC */
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diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 2b4c40b2..d9dee43 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile@@ -76,7 +76,7 @@ endif obj64-$(CONFIG_HIBERNATION) += swsusp_asm64.o obj-$(CONFIG_MODULES) += module.o module_$(BITS).o obj-$(CONFIG_44x) += cpu_setup_44x.o -obj-$(CONFIG_PPC_FSL_BOOK3E) += cpu_setup_fsl_booke.o +obj-$(CONFIG_PPC_FSL_BOOK3E) += cpu_setup_fsl_booke.o security.o obj-$(CONFIG_PPC_DOORBELL) += dbell.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o
Can we instead do: obj-$(CONFIG_PPC_NOSPEC) += security.o
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diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c index c55e102..797c975 100644 --- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c@@ -13,7 +13,9 @@ #include <asm/setup.h> +#ifdef CONFIG_PPC_BOOK3S_64 unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT; +#endif /* CONFIG_PPC_BOOK3S_64 */
Why are you making that book3s specific? By doing that you then can't use the existing versions of setup_barrier_nospec() and cpu_show_spectre_v1/v2().
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@@ -24,6 +26,7 @@ static void enable_barrier_nospec(bool enable) do_barrier_nospec_fixups(enable); } +#ifdef CONFIG_PPC_BOOK3S_64 void setup_barrier_nospec(void) { bool enable;@@ -46,6 +49,15 @@ void setup_barrier_nospec(void) if (!no_nospec) enable_barrier_nospec(enable); } +#endif /* CONFIG_PPC_BOOK3S_64 */ + +#ifdef CONFIG_PPC_FSL_BOOK3E +void setup_barrier_nospec(void) +{ + if (!no_nospec) + enable_barrier_nospec(true); +} +#endif /* CONFIG_PPC_FSL_BOOK3E */
eg. that is identical to the existing version except for the feature check: enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR); Both those bits are enabled by default, so you shouldn't need to elide that check. So basically you should be able to use the existing setup_barrier_nospec() if you just remove the ifdef around powerpc_security_features. Or am I missing something?
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diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c index 7445748..80c1e6e 100644 --- a/arch/powerpc/kernel/setup_32.c +++ b/arch/powerpc/kernel/setup_32.c@@ -116,6 +116,11 @@ notrace void __init machine_init(u64 dt_ptr) /* Do some early initialization based on the flat device tree */ early_init_devtree(__va(dt_ptr)); + /* Apply the speculation barrier fixup */ +#ifdef CONFIG_PPC_FSL_BOOK3E + setup_barrier_nospec(); +#endif
This ifdef should be handled in a header with an empty version for the #else case.
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diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 7a7ce8a..b2a644a 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c@@ -327,6 +327,12 @@ void __init early_setup(unsigned long dt_ptr) /* Apply all the dynamic patching */ apply_feature_fixups(); + + /* Apply the speculation barrier fixup */ +#ifdef CONFIG_PPC_FSL_BOOK3E + setup_barrier_nospec(); +#endif /* CONFIG_PPC_FSL_BOOK3E */
Can you call it from ppc_md->setup_arch() like the other platforms? Failing that we could put it in setup_arch() after the call to ppc_md->setup_arch(), so we can share it with powernv/pseries.
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diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index 2b9173d..bea2b87 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c@@ -188,7 +188,40 @@ void do_barrier_nospec_fixups_range(bool enable, void *fixup_start, void *fixup_ printk(KERN_DEBUG "barrier-nospec: patched %d locations\n", i); } +#endif /* CONFIG_PPC_BOOK3S_64 */ + +#ifdef CONFIG_PPC_FSL_BOOK3E +void do_barrier_nospec_fixups_range(bool enable, void *fixup_start, void *fixup_end) +{ + unsigned int instr[2], *dest; + long *start, *end; + int i; + + start = fixup_start; + end = fixup_end; + + instr[0] = PPC_INST_NOP; + instr[1] = PPC_INST_NOP; + + if (enable) { + pr_info("barrier_nospec; using isync; sync as a speculation barrier\n"); + instr[0] = PPC_INST_ISYNC; + instr[1] = PPC_INST_SYNC; + } + + for (i = 0; start < end; start++, i++) { + dest = (void *)start + *start; + pr_devel("patching dest %lx\n", (unsigned long)dest); + patch_instruction(dest, instr[0]); + patch_instruction(dest + 1, instr[1]); + } + + pr_debug("barrier-nospec: patched %d locations\n", i); +} +#endif /* CONFIG_PPC_FSL_BOOK3E */
It's a bit unfortunate that we end up with two versions of that, which are 80% the same. But merging them without ugly ifdefs would require a bit more refactoring. So I guess it's OK for now. cheers