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[PATCH v2 1/6] x86/microcode/core: Move microcode_check() to cpu/microcode/core.c

Ashok Raj posted 6 patches 2 years, 8 months ago
There is a newer version of this series
[PATCH v2 1/6] x86/microcode/core: Move microcode_check() to cpu/microcode/core.c
Posted by Ashok Raj 2 years, 8 months ago 
microcode_check() is only called from microcode/core.c. Move it and make
it static to prepare for upcoming fix for false negative when checking CPU
features after a microcode update. Also move get_cpu_cap() to processor.h
for general use outside of arch/x86/kernel/cpu/cpu.h

No functional change.

Suggested-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: x86 <x86@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/include/asm/processor.h     |  3 +--
 arch/x86/kernel/cpu/cpu.h            |  1 -
 arch/x86/kernel/cpu/common.c         | 32 ----------------------------
 arch/x86/kernel/cpu/microcode/core.c | 31 +++++++++++++++++++++++++++
 4 files changed, 32 insertions(+), 35 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 4e35c66edeb7..70d01ecc39a4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -182,8 +182,8 @@ extern const struct seq_operations cpuinfo_op;
 
 #define cache_line_size()	(boot_cpu_data.x86_cache_alignment)
 
+extern void get_cpu_cap(struct cpuinfo_x86 *c);
 extern void cpu_detect(struct cpuinfo_x86 *c);
-
 static inline unsigned long long l1tf_pfn_limit(void)
 {
 	return BIT_ULL(boot_cpu_data.x86_cache_bits - 1 - PAGE_SHIFT);
@@ -697,7 +697,6 @@ bool xen_set_default_idle(void);
 #endif
 
 void __noreturn stop_this_cpu(void *dummy);
-void microcode_check(void);
 
 enum l1tf_mitigations {
 	L1TF_MITIGATION_OFF,
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index 7c9b5893c30a..a142b8d543a3 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -63,7 +63,6 @@ static inline void tsx_ap_init(void) { }
 
 extern void init_spectral_chicken(struct cpuinfo_x86 *c);
 
-extern void get_cpu_cap(struct cpuinfo_x86 *c);
 extern void get_cpu_address_sizes(struct cpuinfo_x86 *c);
 extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
 extern void init_scattered_cpuid_features(struct cpuinfo_x86 *c);
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9cfca3d7d0e2..7b06034eeddc 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2296,38 +2296,6 @@ void cpu_init_secondary(void)
 }
 #endif
 
-#ifdef CONFIG_MICROCODE_LATE_LOADING
-/*
- * The microcode loader calls this upon late microcode load to recheck features,
- * only when microcode has been updated. Caller holds microcode_mutex and CPU
- * hotplug lock.
- */
-void microcode_check(void)
-{
-	struct cpuinfo_x86 info;
-
-	perf_check_microcode();
-
-	/* Reload CPUID max function as it might've changed. */
-	info.cpuid_level = cpuid_eax(0);
-
-	/*
-	 * Copy all capability leafs to pick up the synthetic ones so that
-	 * memcmp() below doesn't fail on that. The ones coming from CPUID will
-	 * get overwritten in get_cpu_cap().
-	 */
-	memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability));
-
-	get_cpu_cap(&info);
-
-	if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)))
-		return;
-
-	pr_warn("x86/CPU: CPU features have changed after loading microcode, but might not take effect.\n");
-	pr_warn("x86/CPU: Please consider either early loading through initrd/built-in or a potential BIOS update.\n");
-}
-#endif
-
 /*
  * Invoked from core CPU hotplug code after hotplug operations
  */
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index c4cd7328177b..0051ebf7c53e 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -432,6 +432,37 @@ static int __reload_late(void *info)
 	return ret;
 }
 
+/*
+ * The microcode loader calls this upon late microcode load to recheck features,
+ * only when microcode has been updated. Caller holds microcode_mutex and CPU
+ * hotplug lock.
+ */
+static void microcode_check(void)
+{
+	struct cpuinfo_x86 info;
+
+	perf_check_microcode();
+
+	/* Reload CPUID max function as it might've changed. */
+	info.cpuid_level = cpuid_eax(0);
+
+	/*
+	 * Copy all capability leafs to pick up the synthetic ones so that
+	 * memcmp() below doesn't fail on that. The ones coming from CPUID will
+	 * get overwritten in get_cpu_cap().
+	 */
+	memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability));
+
+	get_cpu_cap(&info);
+
+	if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability,
+		    sizeof(info.x86_capability)))
+		return;
+
+	pr_warn("x86/CPU: CPU features have changed after loading microcode, but might not take effect.\n");
+	pr_warn("x86/CPU: Please consider either early loading through initrd/built-in or a potential BIOS update.\n");
+}
+
 /*
  * Reload microcode late on all CPUs. Wait for a sec until they
  * all gather together.
-- 
2.34.1
Re: [PATCH v2 1/6] x86/microcode/core: Move microcode_check() to cpu/microcode/core.c
Posted by Borislav Petkov 2 years, 8 months ago 
On Tue, Dec 27, 2022 at 11:23:35AM -0800, Ashok Raj wrote:
> microcode_check() is only called from microcode/core.c. Move it and make
> it static to prepare for upcoming fix for false negative when checking CPU
> features after a microcode update. Also move get_cpu_cap() to processor.h
> for general use outside of arch/x86/kernel/cpu/cpu.h

I thought we agreed not to do this:

https://lore.kernel.org/r/Y44bbZMMf8I6Lzl/@zn.tnic

Or was this a misunderstanding?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
Re: [PATCH v2 1/6] x86/microcode/core: Move microcode_check() to cpu/microcode/core.c
Posted by Ashok Raj 2 years, 8 months ago 
On Tue, Dec 27, 2022 at 08:50:25PM +0100, Borislav Petkov wrote:
> On Tue, Dec 27, 2022 at 11:23:35AM -0800, Ashok Raj wrote:
> > microcode_check() is only called from microcode/core.c. Move it and make
> > it static to prepare for upcoming fix for false negative when checking CPU
> > features after a microcode update. Also move get_cpu_cap() to processor.h
> > for general use outside of arch/x86/kernel/cpu/cpu.h
> 
> I thought we agreed not to do this:
> 
> https://lore.kernel.org/r/Y44bbZMMf8I6Lzl/@zn.tnic
> 
> Or was this a misunderstanding?

Bah... you are correct, I should drop this one.

I'll fix it up

Cheers,
Ashok
[PATCH v3 1/2] x86/microcode: Add a parameter to microcode_check() to store CPU capabilities
Posted by Ashok Raj 2 years, 8 months ago 
This is a preparation before the next patch uses this to compare CPU
capabilities after performing an update.

Add a parameter to store CPU capabilities before performing a microcode
update.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: x86 <x86@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/include/asm/processor.h     |  2 +-
 arch/x86/kernel/cpu/common.c         | 12 +++++-------
 arch/x86/kernel/cpu/microcode/core.c |  3 ++-
 3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 4e35c66edeb7..387578049de0 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -697,7 +697,7 @@ bool xen_set_default_idle(void);
 #endif
 
 void __noreturn stop_this_cpu(void *dummy);
-void microcode_check(void);
+void microcode_check(struct cpuinfo_x86 *info);
 
 enum l1tf_mitigations {
 	L1TF_MITIGATION_OFF,
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9cfca3d7d0e2..b9c7529c920e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2302,25 +2302,23 @@ void cpu_init_secondary(void)
  * only when microcode has been updated. Caller holds microcode_mutex and CPU
  * hotplug lock.
  */
-void microcode_check(void)
+void microcode_check(struct cpuinfo_x86 *info)
 {
-	struct cpuinfo_x86 info;
-
 	perf_check_microcode();
 
 	/* Reload CPUID max function as it might've changed. */
-	info.cpuid_level = cpuid_eax(0);
+	info->cpuid_level = cpuid_eax(0);
 
 	/*
 	 * Copy all capability leafs to pick up the synthetic ones so that
 	 * memcmp() below doesn't fail on that. The ones coming from CPUID will
 	 * get overwritten in get_cpu_cap().
 	 */
-	memcpy(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability));
+	memcpy(&info->x86_capability, &boot_cpu_data.x86_capability, sizeof(info->x86_capability));
 
-	get_cpu_cap(&info);
+	get_cpu_cap(info);
 
-	if (!memcmp(&info.x86_capability, &boot_cpu_data.x86_capability, sizeof(info.x86_capability)))
+	if (!memcmp(&info->x86_capability, &boot_cpu_data.x86_capability, sizeof(info->x86_capability)))
 		return;
 
 	pr_warn("x86/CPU: CPU features have changed after loading microcode, but might not take effect.\n");
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index c4cd7328177b..d86a4f910a6b 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -439,6 +439,7 @@ static int __reload_late(void *info)
 static int microcode_reload_late(void)
 {
 	int old = boot_cpu_data.microcode, ret;
+	struct cpuinfo_x86 info;
 
 	pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n");
 	pr_err("You should switch to early loading, if possible.\n");
@@ -448,7 +449,7 @@ static int microcode_reload_late(void)
 
 	ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
 	if (ret == 0)
-		microcode_check();
+		microcode_check(&info);
 
 	pr_info("Reload completed, microcode revision: 0x%x -> 0x%x\n",
 		old, boot_cpu_data.microcode);
-- 
2.34.1
[PATCH v3 2/2] x86/microcode/core: Take a snapshot before and after applying microcode
Posted by Ashok Raj 2 years, 8 months ago 
The kernel caches features about each CPU's features at boot in an
x86_capability[] structure. The microcode update takes one snapshot and
compares it with the saved copy at boot.

However, the capabilities in the boot copy can be turned off as a result of
certain command line parameters or configuration restrictions. This can
cause a mismatch when comparing the values before and after the microcode
update.

microcode_check() is called after an update to report any previously
cached CPUID bits might have changed due to the update.

microcode_store_cpu_caps() basically stores the original CPU reported
values and not the OS modified values. This will avoid giving a false
warning even if no capabilities have changed.

Ignore the capabilities recorded at boot. Take a new snapshot before the
update and compare with a snapshot after the update to eliminate the false
warning.

Fixes: 1008c52c09dc ("x86/CPU: Add a microcode loader callback")
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: x86 <x86@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
---
Changes since last post

- Boris
	- Change function from copy_cpu_caps() -> store_cpu_caps()
	- Keep microcode_check() inside cpu/common.c and not bleed
	  get_cpu_caps() outside of core code.

- Thomas : Commit log changes.
---
 arch/x86/include/asm/processor.h     |  1 +
 arch/x86/kernel/cpu/common.c         | 17 +++++++++++++++++
 arch/x86/kernel/cpu/microcode/core.c |  7 +++++++
 3 files changed, 25 insertions(+)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 387578049de0..ac2e67156b9b 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -697,6 +697,7 @@ bool xen_set_default_idle(void);
 #endif
 
 void __noreturn stop_this_cpu(void *dummy);
+void microcode_store_cpu_caps(struct cpuinfo_x86 *info);
 void microcode_check(struct cpuinfo_x86 *info);
 
 enum l1tf_mitigations {
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b9c7529c920e..1f0b57a5d89d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2297,6 +2297,23 @@ void cpu_init_secondary(void)
 #endif
 
 #ifdef CONFIG_MICROCODE_LATE_LOADING
+
+void microcode_store_cpu_caps(struct cpuinfo_x86 *info)
+{
+	/* Reload CPUID max function as it might've changed. */
+	info->cpuid_level = cpuid_eax(0);
+
+	/*
+	 * Copy all capability leafs to pick up the synthetic ones so that
+	 * memcmp() below doesn't fail on that. The ones coming from CPUID will
+	 * get overwritten in get_cpu_cap().
+	 */
+	memcpy(info->x86_capability, &boot_cpu_data.x86_capability,
+	       sizeof(info->x86_capability));
+
+	get_cpu_cap(info);
+}
+
 /*
  * The microcode loader calls this upon late microcode load to recheck features,
  * only when microcode has been updated. Caller holds microcode_mutex and CPU
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index d86a4f910a6b..14d9031ed68a 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -447,6 +447,13 @@ static int microcode_reload_late(void)
 	atomic_set(&late_cpus_in,  0);
 	atomic_set(&late_cpus_out, 0);
 
+	/*
+	 * Take a snapshot before the microcode update, so we can compare
+	 * them after the update is successful to check for any bits
+	 * changed.
+	 */
+	microcode_store_cpu_caps(&info);
+
 	ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
 	if (ret == 0)
 		microcode_check(&info);
-- 
2.34.1
Re: [PATCH v3 2/2] x86/microcode/core: Take a snapshot before and after applying microcode
Posted by Ashok Raj 2 years, 8 months ago 
On Tue, Dec 27, 2022 at 01:01:44PM -0800, Ashok Raj wrote:
> The kernel caches features about each CPU's features at boot in an
> x86_capability[] structure. The microcode update takes one snapshot and
> compares it with the saved copy at boot.
> 
> However, the capabilities in the boot copy can be turned off as a result of
> certain command line parameters or configuration restrictions. This can
> cause a mismatch when comparing the values before and after the microcode
> update.
> 
> microcode_check() is called after an update to report any previously
> cached CPUID bits might have changed due to the update.
> 

I'll send you a clean version. Somehow this picked up an interim change and
the change to microcode_check() is not there. I remember testing but it
happened to be a different system I updated. 

I'll send something after the new years.. working during holidays isn't
efficient :-(.


Cheers,
Ashok

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