x86/sev: Fix SNP host late disable

[PATCH 2/5] x86/alternatives: Catch late X86_FEATURE modifiers

Posted by Borislav Petkov 1 year, 10 months ago

From: "Borislav Petkov (AMD)" <bp@alien8.de>

After alternatives have been patched, changes to the X86_FEATURE flags
won't take effect and could potentially even be wrong.

Warn about it.

This is something which has been long overdue.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/cpufeature.h | 8 ++++++--
 arch/x86/kernel/cpu/cpuid-deps.c  | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 1ef620d508f4..d0b9c411144b 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -146,8 +146,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 extern void setup_clear_cpu_cap(unsigned int bit);
 extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
 
-#define setup_force_cpu_cap(bit) do { \
-	set_cpu_cap(&boot_cpu_data, bit);	\
+#define setup_force_cpu_cap(bit) do {			\
+							\
+	if (!boot_cpu_has(bit))				\
+		WARN_ON(alternatives_patched);		\
+							\
+	set_cpu_cap(&boot_cpu_data, bit);		\
 	set_bit(bit, (unsigned long *)cpu_caps_set);	\
 } while (0)
 
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index b7174209d855..5dd427c6feb2 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
 	if (WARN_ON(feature >= MAX_FEATURE_BITS))
 		return;
 
+	if (boot_cpu_has(feature))
+		WARN_ON(alternatives_patched);
+
 	clear_feature(c, feature);
 
 	/* Collect all features to disable, handling dependencies */
-- 
2.43.0

Re: [PATCH 2/5] x86/alternatives: Catch late X86_FEATURE modifiers

Posted by Nikolay Borisov 1 year, 10 months ago


On 27.03.24 г. 17:43 ч., Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> After alternatives have been patched, changes to the X86_FEATURE flags
> won't take effect and could potentially even be wrong.
> 
> Warn about it.
> 
> This is something which has been long overdue.
> 
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>

nit: While cleaning this bit mind if you also switch 
alternatives_patched to a bool?

Re: [PATCH 2/5] x86/alternatives: Catch late X86_FEATURE modifiers

Posted by Borislav Petkov 1 year, 10 months ago

On Wed, Mar 27, 2024 at 05:57:01PM +0200, Nikolay Borisov wrote:
> nit: While cleaning this bit mind if you also switch alternatives_patched to
> a bool?

Busy as hell right now. But I take patches ontop. :-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

[tip: x86/alternatives] x86/alternatives: Catch late X86_FEATURE modifiers

Posted by tip-bot2 for Borislav Petkov (AMD) 1 year, 10 months ago

The following commit has been merged into the x86/alternatives branch of tip:

Commit-ID:     ee8962082a4413dba1a1b3d3d23490c5221f3b8a
Gitweb:        https://git.kernel.org/tip/ee8962082a4413dba1a1b3d3d23490c5221f3b8a
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Wed, 27 Mar 2024 16:43:14 +01:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 09 Apr 2024 18:03:53 +02:00

x86/alternatives: Catch late X86_FEATURE modifiers

After alternatives have been patched, changes to the X86_FEATURE flags
won't take effect and could potentially even be wrong.

Warn about it.

This is something which has been long overdue.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Link: https://lore.kernel.org/r/20240327154317.29909-3-bp@alien8.de
---
 arch/x86/include/asm/cpufeature.h | 8 ++++++--
 arch/x86/kernel/cpu/cpuid-deps.c  | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 686e92d..f07687d 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -150,8 +150,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 extern void setup_clear_cpu_cap(unsigned int bit);
 extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
 
-#define setup_force_cpu_cap(bit) do { \
-	set_cpu_cap(&boot_cpu_data, bit);	\
+#define setup_force_cpu_cap(bit) do {			\
+							\
+	if (!boot_cpu_has(bit))				\
+		WARN_ON(alternatives_patched);		\
+							\
+	set_cpu_cap(&boot_cpu_data, bit);		\
 	set_bit(bit, (unsigned long *)cpu_caps_set);	\
 } while (0)
 
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index b717420..5dd427c 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
 	if (WARN_ON(feature >= MAX_FEATURE_BITS))
 		return;
 
+	if (boot_cpu_has(feature))
+		WARN_ON(alternatives_patched);
+
 	clear_feature(c, feature);
 
 	/* Collect all features to disable, handling dependencies */

[tip: x86/alternatives] x86/alternatives: Catch late X86_FEATURE modifiers

Posted by tip-bot2 for Borislav Petkov (AMD) 1 year, 10 months ago

The following commit has been merged into the x86/alternatives branch of tip:

Commit-ID:     4175b45dec4cd8ae4563bf724d591ab5cc0ad9ce
Gitweb:        https://git.kernel.org/tip/4175b45dec4cd8ae4563bf724d591ab5cc0ad9ce
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Wed, 27 Mar 2024 16:43:14 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 04 Apr 2024 12:09:17 +02:00

x86/alternatives: Catch late X86_FEATURE modifiers

After alternatives have been patched, changes to the X86_FEATURE flags
won't take effect and could potentially even be wrong.

Warn about it.

This is something which has been long overdue.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Link: https://lore.kernel.org/r/20240327154317.29909-3-bp@alien8.de
---
 arch/x86/include/asm/cpufeature.h | 8 ++++++--
 arch/x86/kernel/cpu/cpuid-deps.c  | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 17fd7be..f8d7a06 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -148,8 +148,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 extern void setup_clear_cpu_cap(unsigned int bit);
 extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
 
-#define setup_force_cpu_cap(bit) do { \
-	set_cpu_cap(&boot_cpu_data, bit);	\
+#define setup_force_cpu_cap(bit) do {			\
+							\
+	if (!boot_cpu_has(bit))				\
+		WARN_ON(alternatives_patched);		\
+							\
+	set_cpu_cap(&boot_cpu_data, bit);		\
 	set_bit(bit, (unsigned long *)cpu_caps_set);	\
 } while (0)
 
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index b717420..5dd427c 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
 	if (WARN_ON(feature >= MAX_FEATURE_BITS))
 		return;
 
+	if (boot_cpu_has(feature))
+		WARN_ON(alternatives_patched);
+
 	clear_feature(c, feature);
 
 	/* Collect all features to disable, handling dependencies */

[tip: x86/alternatives] x86/alternatives: Catch late X86_FEATURE modifiers

Posted by tip-bot2 for Borislav Petkov (AMD) 1 year, 10 months ago

The following commit has been merged into the x86/alternatives branch of tip:

Commit-ID:     97784e52f18fe6e0d6516ded8ecd3cec722ce9cc
Gitweb:        https://git.kernel.org/tip/97784e52f18fe6e0d6516ded8ecd3cec722ce9cc
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Wed, 27 Mar 2024 16:43:14 +01:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Wed, 03 Apr 2024 20:03:24 +02:00

x86/alternatives: Catch late X86_FEATURE modifiers

After alternatives have been patched, changes to the X86_FEATURE flags
won't take effect and could potentially even be wrong.

Warn about it.

This is something which has been long overdue.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Link: https://lore.kernel.org/r/20240327154317.29909-3-bp@alien8.de
---
 arch/x86/include/asm/cpufeature.h | 8 ++++++--
 arch/x86/kernel/cpu/cpuid-deps.c  | 3 +++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 7103ba1..e5d8880 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -148,8 +148,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 extern void setup_clear_cpu_cap(unsigned int bit);
 extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
 
-#define setup_force_cpu_cap(bit) do { \
-	set_cpu_cap(&boot_cpu_data, bit);	\
+#define setup_force_cpu_cap(bit) do {			\
+							\
+	if (!boot_cpu_has(bit))				\
+		WARN_ON(alternatives_patched);		\
+							\
+	set_cpu_cap(&boot_cpu_data, bit);		\
 	set_bit(bit, (unsigned long *)cpu_caps_set);	\
 } while (0)
 
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index b717420..5dd427c 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -114,6 +114,9 @@ static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
 	if (WARN_ON(feature >= MAX_FEATURE_BITS))
 		return;
 
+	if (boot_cpu_has(feature))
+		WARN_ON(alternatives_patched);
+
 	clear_feature(c, feature);
 
 	/* Collect all features to disable, handling dependencies */