* [PATCH v2] x86/retpoline: Only set RETPOLINE_AMD if LFENCE is serializing
@ 2018-01-10 0:39 Tom Lendacky
2018-01-10 0:51 ` [tip:x86/pti] " tip-bot for Tom Lendacky
0 siblings, 1 reply; 2+ messages in thread
From: Tom Lendacky @ 2018-01-10 0:39 UTC (permalink / raw)
To: x86, linux-kernel
Cc: Rik van Riel, Andi Kleen, Peter Zijlstra, Linus Torvalds,
Jiri Kosina, Dan Williams, Dave Hansen, Borislav Petkov,
Andy Lutomirski, Kees Cook, Thomas Gleixner, Tim Chen,
Greg Kroah-Hartman, David Woodhouse, Paul Turner
The RETPOLINE_AMD feature relies on a serializing LFENCE for speculation
control. For AMD hardware, only set RETPOLINE_AMD if LFENCE is a
serializing instruction, which is indicated by the LFENCE_RDTSC feature.
The call to spectre_v2_check_boottime_disable() is currently before the
boot CPU is identified and, therefore, able to set the LFENCE_RDTSC
feature. Move the call to spectre_v2_check_boottime_disable() to after
identify_boot_cpu() in check_bugs().
Also, protect against specifying spectre_v2=retpoline,amd for non-AMD
hardware and fall-back to the generic retpoline.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/x86/include/asm/nospec-branch.h | 2 --
arch/x86/kernel/cpu/bugs.c | 22 +++++++++++++++++-----
arch/x86/kernel/setup.c | 2 --
3 files changed, 17 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 8ddf851..6bda2c0 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -152,7 +152,5 @@
# define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
#endif
-void spectre_v2_check_boottime_disable(void);
-
#endif /* __ASSEMBLY__ */
#endif /* __NOSPEC_BRANCH_H__ */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b957f77..815dee2 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -24,6 +24,8 @@
#include <asm/pgtable.h>
#include <asm/set_memory.h>
+static void __init spectre_v2_check_boottime_disable(void);
+
void __init check_bugs(void)
{
identify_boot_cpu();
@@ -33,6 +35,9 @@ void __init check_bugs(void)
print_cpu_info(&boot_cpu_data);
}
+ /* Select the proper spectre mitigation before patching alternatives */
+ spectre_v2_check_boottime_disable();
+
#ifdef CONFIG_X86_32
/*
* Check whether we are able to run this kernel safely on SMP.
@@ -106,7 +111,7 @@ static inline bool match_option(const char *arg, int arglen, const char *opt)
return len == arglen && !strncmp(arg, opt, len);
}
-void __init spectre_v2_check_boottime_disable(void)
+static void __init spectre_v2_check_boottime_disable(void)
{
char arg[20];
int ret;
@@ -148,14 +153,21 @@ void __init spectre_v2_check_boottime_disable(void)
retpoline:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
retpoline_amd:
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD ||
+ !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
+ pr_info("AMD retpoline not supported, fall back to generic\n");
+ goto retpoline_generic;
+ }
+
spectre_v2_enabled = retp_compiler() ?
SPECTRE_V2_RETPOLINE_AMD : SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
- } else {
- retpoline_generic:
- spectre_v2_enabled = retp_compiler() ?
- SPECTRE_V2_RETPOLINE_GENERIC : SPECTRE_V2_RETPOLINE_MINIMAL;
+ setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
+ return;
}
+retpoline_generic:
+ spectre_v2_enabled = retp_compiler() ?
+ SPECTRE_V2_RETPOLINE_GENERIC : SPECTRE_V2_RETPOLINE_MINIMAL;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
return;
#else
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9fb4f9d..b5a908b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1322,8 +1322,6 @@ void __init setup_arch(char **cmdline_p)
register_refined_jiffies(CLOCK_TICK_RATE);
- spectre_v2_check_boottime_disable();
-
#ifdef CONFIG_EFI
if (efi_enabled(EFI_BOOT))
efi_apply_memmap_quirks();
^ permalink raw reply [flat|nested] 2+ messages in thread
* [tip:x86/pti] x86/retpoline: Only set RETPOLINE_AMD if LFENCE is serializing
2018-01-10 0:39 [PATCH v2] x86/retpoline: Only set RETPOLINE_AMD if LFENCE is serializing Tom Lendacky
@ 2018-01-10 0:51 ` tip-bot for Tom Lendacky
0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Tom Lendacky @ 2018-01-10 0:51 UTC (permalink / raw)
To: linux-tip-commits
Cc: dan.j.williams, gregkh, pjt, riel, dwmw, dave.hansen, luto, hpa,
thomas.lendacky, jikos, tglx, ak, linux-kernel, mingo, torvalds,
tim.c.chen, keescook, bp, peterz
Commit-ID: b10d070a67d96db93223d11832c1e74588d7d566
Gitweb: https://git.kernel.org/tip/b10d070a67d96db93223d11832c1e74588d7d566
Author: Tom Lendacky <thomas.lendacky@amd.com>
AuthorDate: Tue, 9 Jan 2018 18:39:31 -0600
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 10 Jan 2018 01:49:13 +0100
x86/retpoline: Only set RETPOLINE_AMD if LFENCE is serializing
The RETPOLINE_AMD feature relies on a serializing LFENCE for speculation
control. For AMD hardware, only set RETPOLINE_AMD if LFENCE is a
serializing instruction, which is indicated by the LFENCE_RDTSC feature.
The call to spectre_v2_check_boottime_disable() is currently before the
boot CPU is identified and, therefore, able to set the LFENCE_RDTSC
feature. Move the call to spectre_v2_check_boottime_disable() to after
identify_boot_cpu() in check_bugs().
Also, protect against specifying spectre_v2=retpoline,amd for non-AMD
hardware and fall-back to the generic retpoline.
54d5103245ff ("x86/spectre: Add boot time option to select Spectre v2 mitigation")
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/20180110003931.32411.55646.stgit@tlendack-t1.amdoffice.net
---
arch/x86/include/asm/nospec-branch.h | 2 --
arch/x86/kernel/cpu/bugs.c | 22 +++++++++++++++++-----
arch/x86/kernel/setup.c | 2 --
3 files changed, 17 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 8ddf851..6bda2c0 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -152,7 +152,5 @@
# define THUNK_TARGET(addr) [thunk_target] "rm" (addr)
#endif
-void spectre_v2_check_boottime_disable(void);
-
#endif /* __ASSEMBLY__ */
#endif /* __NOSPEC_BRANCH_H__ */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b957f77..815dee2 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -24,6 +24,8 @@
#include <asm/pgtable.h>
#include <asm/set_memory.h>
+static void __init spectre_v2_check_boottime_disable(void);
+
void __init check_bugs(void)
{
identify_boot_cpu();
@@ -33,6 +35,9 @@ void __init check_bugs(void)
print_cpu_info(&boot_cpu_data);
}
+ /* Select the proper spectre mitigation before patching alternatives */
+ spectre_v2_check_boottime_disable();
+
#ifdef CONFIG_X86_32
/*
* Check whether we are able to run this kernel safely on SMP.
@@ -106,7 +111,7 @@ static inline bool match_option(const char *arg, int arglen, const char *opt)
return len == arglen && !strncmp(arg, opt, len);
}
-void __init spectre_v2_check_boottime_disable(void)
+static void __init spectre_v2_check_boottime_disable(void)
{
char arg[20];
int ret;
@@ -148,14 +153,21 @@ force:
retpoline:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
retpoline_amd:
+ if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD ||
+ !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
+ pr_info("AMD retpoline not supported, fall back to generic\n");
+ goto retpoline_generic;
+ }
+
spectre_v2_enabled = retp_compiler() ?
SPECTRE_V2_RETPOLINE_AMD : SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
- } else {
- retpoline_generic:
- spectre_v2_enabled = retp_compiler() ?
- SPECTRE_V2_RETPOLINE_GENERIC : SPECTRE_V2_RETPOLINE_MINIMAL;
+ setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
+ return;
}
+retpoline_generic:
+ spectre_v2_enabled = retp_compiler() ?
+ SPECTRE_V2_RETPOLINE_GENERIC : SPECTRE_V2_RETPOLINE_MINIMAL;
setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
return;
#else
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9fb4f9d..b5a908b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1322,8 +1322,6 @@ void __init setup_arch(char **cmdline_p)
register_refined_jiffies(CLOCK_TICK_RATE);
- spectre_v2_check_boottime_disable();
-
#ifdef CONFIG_EFI
if (efi_enabled(EFI_BOOT))
efi_apply_memmap_quirks();
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2018-01-10 0:58 UTC | newest]
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2018-01-10 0:39 [PATCH v2] x86/retpoline: Only set RETPOLINE_AMD if LFENCE is serializing Tom Lendacky
2018-01-10 0:51 ` [tip:x86/pti] " tip-bot for Tom Lendacky
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