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Subject[PATCH 4.4.y 037/101] x86/speculation: Clean up various Spectre related details
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Date
From: Ingo Molnar <mingo@kernel.org>

commit 21e433bdb95bdf3aa48226fd3d33af608437f293 upstream.

Harmonize all the Spectre messages so that a:

dmesg | grep -i spectre

... gives us most Spectre related kernel boot messages.

Also fix a few other details:

- clarify a comment about firmware speculation control

- s/KPTI/PTI

- remove various line-breaks that made the code uglier

Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Matt Helsley (VMware) <matt.helsley@gmail.com>
Reviewed-by: Alexey Makhalov <amakhalov@vmware.com>
Reviewed-by: Bo Gan <ganb@vmware.com>
---

arch/x86/kernel/cpu/bugs.c | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1968baf..fea368d 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -162,8 +162,7 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
return SPECTRE_V2_CMD_NONE;
else {
- ret = cmdline_find_option(boot_command_line, "spectre_v2", arg,
- sizeof(arg));
+ ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
if (ret < 0)
return SPECTRE_V2_CMD_AUTO;

@@ -184,8 +183,7 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
!IS_ENABLED(CONFIG_RETPOLINE)) {
- pr_err("%s selected but not compiled in. Switching to AUTO select\n",
- mitigation_options[i].option);
+ pr_err("%s selected but not compiled in. Switching to AUTO select\n", mitigation_options[i].option);
return SPECTRE_V2_CMD_AUTO;
}

@@ -255,14 +253,14 @@ static void __init spectre_v2_select_mitigation(void)
goto retpoline_auto;
break;
}
- pr_err("kernel not compiled with retpoline; no mitigation available!");
+ pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
return;

retpoline_auto:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
retpoline_amd:
if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
- pr_err("LFENCE not serializing. Switching to generic retpoline\n");
+ pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
goto retpoline_generic;
}
mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
@@ -280,7 +278,7 @@ retpoline_auto:
pr_info("%s\n", spectre_v2_strings[mode]);

/*
- * If neither SMEP or KPTI are available, there is a risk of
+ * If neither SMEP nor PTI are available, there is a risk of
* hitting userspace addresses in the RSB after a context switch
* from a shallow call stack to a deeper one. To prevent this fill
* the entire RSB, even when using IBRS.
@@ -294,21 +292,20 @@ retpoline_auto:
if ((!boot_cpu_has(X86_FEATURE_KAISER) &&
!boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
- pr_info("Filling RSB on context switch\n");
+ pr_info("Spectre v2 mitigation: Filling RSB on context switch\n");
}

/* Initialize Indirect Branch Prediction Barrier if supported */
if (boot_cpu_has(X86_FEATURE_IBPB)) {
setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
- pr_info("Enabling Indirect Branch Prediction Barrier\n");
+ pr_info("Spectre v2 mitigation: Enabling Indirect Branch Prediction Barrier\n");
}
}

#undef pr_fmt

#ifdef CONFIG_SYSFS
-ssize_t cpu_show_meltdown(struct device *dev,
- struct device_attribute *attr, char *buf)
+ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
{
if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
return sprintf(buf, "Not affected\n");
@@ -317,16 +314,14 @@ ssize_t cpu_show_meltdown(struct device *dev,
return sprintf(buf, "Vulnerable\n");
}

-ssize_t cpu_show_spectre_v1(struct device *dev,
- struct device_attribute *attr, char *buf)
+ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
return sprintf(buf, "Not affected\n");
return sprintf(buf, "Mitigation: __user pointer sanitization\n");
}

-ssize_t cpu_show_spectre_v2(struct device *dev,
- struct device_attribute *attr, char *buf)
+ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
{
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
return sprintf(buf, "Not affected\n");
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