[PATCH 0/3] x86/bugs: Some SRSO fixes

[PATCH 0/3] x86/bugs: Some SRSO fixes

[Borislav Petkov]

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

Hi all,

those are the leftover smaller fixes which can go after the release
date. I'll queue them next week.

Thx.

Borislav Petkov (AMD) (3):
  Documentation/hw-vuln: Unify filename specification in index
  driver core: cpu: Unify redundant silly stubs
  Documentation/srso: Document IBPB aspect and fix formatting

 Documentation/admin-guide/hw-vuln/index.rst | 12 +--
 Documentation/admin-guide/hw-vuln/srso.rst  | 71 ++++++++++-------
 drivers/base/cpu.c                          | 86 +++++----------------
 3 files changed, 68 insertions(+), 101 deletions(-)

-- 
2.41.0

[PATCH 1/3] Documentation/hw-vuln: Unify filename specification in index

[Borislav Petkov]

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

Most of the index.rst files in Documentation/ refer to other rst files
without their file extension in the name. Do that here too.

No functional changes.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 Documentation/admin-guide/hw-vuln/index.rst | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
index a7d37e124831..aeee8bff5f82 100644
--- a/Documentation/admin-guide/hw-vuln/index.rst
+++ b/Documentation/admin-guide/hw-vuln/index.rst
@@ -13,11 +13,11 @@ are configurable at compile, boot or run time.
    l1tf
    mds
    tsx_async_abort
-   multihit.rst
-   special-register-buffer-data-sampling.rst
-   core-scheduling.rst
-   l1d_flush.rst
-   processor_mmio_stale_data.rst
-   cross-thread-rsb.rst
+   multihit
+   special-register-buffer-data-sampling
+   core-scheduling
+   l1d_flush
+   processor_mmio_stale_data
+   cross-thread-rsb
    srso
    gather_data_sampling.rst
-- 
2.41.0

Re: [PATCH 1/3] Documentation/hw-vuln: Unify filename specification in index

[Pawan Gupta]

On Wed, Aug 09, 2023 at 12:26:58PM +0200, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> Most of the index.rst files in Documentation/ refer to other rst files
> without their file extension in the name. Do that here too.
> 
> No functional changes.
> 
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> ---
>  Documentation/admin-guide/hw-vuln/index.rst | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
> index a7d37e124831..aeee8bff5f82 100644
> --- a/Documentation/admin-guide/hw-vuln/index.rst
> +++ b/Documentation/admin-guide/hw-vuln/index.rst
> @@ -13,11 +13,11 @@ are configurable at compile, boot or run time.
>     l1tf
>     mds
>     tsx_async_abort
> -   multihit.rst
> -   special-register-buffer-data-sampling.rst
> -   core-scheduling.rst
> -   l1d_flush.rst
> -   processor_mmio_stale_data.rst
> -   cross-thread-rsb.rst
> +   multihit
> +   special-register-buffer-data-sampling
> +   core-scheduling
> +   l1d_flush
> +   processor_mmio_stale_data
> +   cross-thread-rsb
>     srso
>     gather_data_sampling.rst

While at it could you please also change this? Else, I will send another
patch.

Re: [PATCH 1/3] Documentation/hw-vuln: Unify filename specification in index

[Borislav Petkov]

On Wed, Aug 09, 2023 at 02:32:14PM -0700, Pawan Gupta wrote:
> While at it could you please also change this?

Yes, I can.

Thx.

-- 
Regards/Gruss,
    Boris.

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

[tip: x86/bugs] Documentation/hw-vuln: Unify filename specification in index

[tip-bot2 for Borislav Petkov (AMD)]

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

Commit-ID:     182ac87070e26d32a01445cec7ca7afa07411468
Gitweb:        https://git.kernel.org/tip/182ac87070e26d32a01445cec7ca7afa07411468
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Sat, 29 Jul 2023 16:53:02 +02:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Thu, 10 Aug 2023 10:48:12 +02:00

Documentation/hw-vuln: Unify filename specification in index

Most of the index.rst files in Documentation/ refer to other rst files
without their file extension in the name. Do that here too.

No functional changes.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230809102700.29449-2-bp@alien8.de
---
 Documentation/admin-guide/hw-vuln/index.rst | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
index a7d37e1..de99caa 100644
--- a/Documentation/admin-guide/hw-vuln/index.rst
+++ b/Documentation/admin-guide/hw-vuln/index.rst
@@ -13,11 +13,11 @@ are configurable at compile, boot or run time.
    l1tf
    mds
    tsx_async_abort
-   multihit.rst
-   special-register-buffer-data-sampling.rst
-   core-scheduling.rst
-   l1d_flush.rst
-   processor_mmio_stale_data.rst
-   cross-thread-rsb.rst
+   multihit
+   special-register-buffer-data-sampling
+   core-scheduling
+   l1d_flush
+   processor_mmio_stale_data
+   cross-thread-rsb
    srso
-   gather_data_sampling.rst
+   gather_data_sampling

[PATCH 2/3] driver core: cpu: Unify redundant silly stubs

[Borislav Petkov]

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

Make them all a weak function, aliasing to a single function which
issues the "Not affected" string.

No functional changes.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 drivers/base/cpu.c | 86 ++++++++++------------------------------------
 1 file changed, 18 insertions(+), 68 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 52df435eecf8..971771347aa6 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -509,79 +509,29 @@ static void __init cpu_dev_register_generic(void)
 }
 
 #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
-
-ssize_t __weak cpu_show_meltdown(struct device *dev,
-				 struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spectre_v1(struct device *dev,
-				   struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spectre_v2(struct device *dev,
-				   struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spec_store_bypass(struct device *dev,
-					  struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_l1tf(struct device *dev,
-			     struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_mds(struct device *dev,
-			    struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_tsx_async_abort(struct device *dev,
-					struct device_attribute *attr,
-					char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_itlb_multihit(struct device *dev,
-				      struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_srbds(struct device *dev,
+ssize_t cpu_show_not_affected(struct device *dev,
 			      struct device_attribute *attr, char *buf)
 {
 	return sysfs_emit(buf, "Not affected\n");
 }
 
-ssize_t __weak cpu_show_mmio_stale_data(struct device *dev,
-					struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_retbleed(struct device *dev,
-				 struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spec_rstack_overflow(struct device *dev,
-					     struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
+#define CPU_VULN_FALLBACK(func)						\
+	ssize_t cpu_show_##func(struct device *,			\
+				  struct device_attribute *, char *)	\
+		 __attribute__((weak, alias("cpu_show_not_affected")))
+
+CPU_VULN_FALLBACK(meltdown);
+CPU_VULN_FALLBACK(spectre_v1);
+CPU_VULN_FALLBACK(spectre_v2);
+CPU_VULN_FALLBACK(spec_store_bypass);
+CPU_VULN_FALLBACK(l1tf);
+CPU_VULN_FALLBACK(mds);
+CPU_VULN_FALLBACK(tsx_async_abort);
+CPU_VULN_FALLBACK(itlb_multihit);
+CPU_VULN_FALLBACK(srbds);
+CPU_VULN_FALLBACK(mmio_stale_data);
+CPU_VULN_FALLBACK(retbleed);
+CPU_VULN_FALLBACK(spec_rstack_overflow);
 
 ssize_t __weak cpu_show_gds(struct device *dev,
 			    struct device_attribute *attr, char *buf)
-- 
2.41.0

Re: [PATCH 2/3] driver core: cpu: Unify redundant silly stubs

[Nikolay Borisov]

On 9.08.23 г. 13:26 ч., Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> Make them all a weak function, aliasing to a single function which
> issues the "Not affected" string.
> 
> No functional changes.
> 
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>


Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>

Re: [PATCH 2/3] driver core: cpu: Unify redundant silly stubs

[Pawan Gupta]

On Wed, Aug 09, 2023 at 12:26:59PM +0200, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> Make them all a weak function, aliasing to a single function which
> issues the "Not affected" string.
> 
> No functional changes.
> 
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> ---
>  drivers/base/cpu.c | 86 ++++++++++------------------------------------
>  1 file changed, 18 insertions(+), 68 deletions(-)
> 
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 52df435eecf8..971771347aa6 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -509,79 +509,29 @@ static void __init cpu_dev_register_generic(void)
>  }
>  
>  #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
> -
> -ssize_t __weak cpu_show_meltdown(struct device *dev,
> -				 struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_spectre_v1(struct device *dev,
> -				   struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_spectre_v2(struct device *dev,
> -				   struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_spec_store_bypass(struct device *dev,
> -					  struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_l1tf(struct device *dev,
> -			     struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_mds(struct device *dev,
> -			    struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_tsx_async_abort(struct device *dev,
> -					struct device_attribute *attr,
> -					char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_itlb_multihit(struct device *dev,
> -				      struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_srbds(struct device *dev,
> +ssize_t cpu_show_not_affected(struct device *dev,
>  			      struct device_attribute *attr, char *buf)
>  {
>  	return sysfs_emit(buf, "Not affected\n");
>  }
>  
> -ssize_t __weak cpu_show_mmio_stale_data(struct device *dev,
> -					struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_retbleed(struct device *dev,
> -				 struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> -
> -ssize_t __weak cpu_show_spec_rstack_overflow(struct device *dev,
> -					     struct device_attribute *attr, char *buf)
> -{
> -	return sysfs_emit(buf, "Not affected\n");
> -}
> +#define CPU_VULN_FALLBACK(func)						\

Nit, its not actually a vulnerability fallback, does
CPU_SHOW_VULN_FALLBACK() sound better?

> +	ssize_t cpu_show_##func(struct device *,			\
> +				  struct device_attribute *, char *)	\
> +		 __attribute__((weak, alias("cpu_show_not_affected")))
> +
> +CPU_VULN_FALLBACK(meltdown);
> +CPU_VULN_FALLBACK(spectre_v1);
> +CPU_VULN_FALLBACK(spectre_v2);
> +CPU_VULN_FALLBACK(spec_store_bypass);
> +CPU_VULN_FALLBACK(l1tf);
> +CPU_VULN_FALLBACK(mds);
> +CPU_VULN_FALLBACK(tsx_async_abort);
> +CPU_VULN_FALLBACK(itlb_multihit);
> +CPU_VULN_FALLBACK(srbds);
> +CPU_VULN_FALLBACK(mmio_stale_data);
> +CPU_VULN_FALLBACK(retbleed);
> +CPU_VULN_FALLBACK(spec_rstack_overflow);
>  
>  ssize_t __weak cpu_show_gds(struct device *dev,
>  			    struct device_attribute *attr, char *buf)

Do you want me to send a separate patch for this?

Re: [PATCH 2/3] driver core: cpu: Unify redundant silly stubs

[Borislav Petkov]

On Wed, Aug 09, 2023 at 02:47:41PM -0700, Pawan Gupta wrote:
> Do you want me to send a separate patch for this?

No need - I'll fix it up.

Thx.

-- 
Regards/Gruss,
    Boris.

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

[tip: x86/bugs] driver core: cpu: Unify redundant silly stubs

[tip-bot2 for Borislav Petkov (AMD)]

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

Commit-ID:     0fddfe338210aa018137c03030c581f5ea4be282
Gitweb:        https://git.kernel.org/tip/0fddfe338210aa018137c03030c581f5ea4be282
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Sat, 29 Jul 2023 17:20:33 +02:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Thu, 10 Aug 2023 11:03:04 +02:00

driver core: cpu: Unify redundant silly stubs

Make them all a weak function, aliasing to a single function which
issues the "Not affected" string.

No functional changes.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/r/20230809102700.29449-3-bp@alien8.de
---
 drivers/base/cpu.c | 87 +++++++++------------------------------------
 1 file changed, 19 insertions(+), 68 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 52df435..054c81b 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -509,79 +509,30 @@ static void __init cpu_dev_register_generic(void)
 }
 
 #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
-
-ssize_t __weak cpu_show_meltdown(struct device *dev,
-				 struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spectre_v1(struct device *dev,
-				   struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spectre_v2(struct device *dev,
-				   struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spec_store_bypass(struct device *dev,
-					  struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_l1tf(struct device *dev,
-			     struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_mds(struct device *dev,
-			    struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_tsx_async_abort(struct device *dev,
-					struct device_attribute *attr,
-					char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_itlb_multihit(struct device *dev,
-				      struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_srbds(struct device *dev,
+ssize_t cpu_show_not_affected(struct device *dev,
 			      struct device_attribute *attr, char *buf)
 {
 	return sysfs_emit(buf, "Not affected\n");
 }
 
-ssize_t __weak cpu_show_mmio_stale_data(struct device *dev,
-					struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_retbleed(struct device *dev,
-				 struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
-
-ssize_t __weak cpu_show_spec_rstack_overflow(struct device *dev,
-					     struct device_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "Not affected\n");
-}
+#define CPU_SHOW_VULN_FALLBACK(func)					\
+	ssize_t cpu_show_##func(struct device *,			\
+				  struct device_attribute *, char *)	\
+		 __attribute__((weak, alias("cpu_show_not_affected")))
+
+CPU_SHOW_VULN_FALLBACK(meltdown);
+CPU_SHOW_VULN_FALLBACK(spectre_v1);
+CPU_SHOW_VULN_FALLBACK(spectre_v2);
+CPU_SHOW_VULN_FALLBACK(spec_store_bypass);
+CPU_SHOW_VULN_FALLBACK(l1tf);
+CPU_SHOW_VULN_FALLBACK(mds);
+CPU_SHOW_VULN_FALLBACK(tsx_async_abort);
+CPU_SHOW_VULN_FALLBACK(itlb_multihit);
+CPU_SHOW_VULN_FALLBACK(srbds);
+CPU_SHOW_VULN_FALLBACK(mmio_stale_data);
+CPU_SHOW_VULN_FALLBACK(retbleed);
+CPU_SHOW_VULN_FALLBACK(spec_rstack_overflow);
+CPU_SHOW_VULN_FALLBACK(gather_data_sampling);
 
 ssize_t __weak cpu_show_gds(struct device *dev,
 			    struct device_attribute *attr, char *buf)

[PATCH 3/3] Documentation/srso: Document IBPB aspect and fix formatting

[Borislav Petkov]

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

Add a note about the dependency of the User->User mitigation on the
previous Spectre v2 IBPB selection.

Make the layout moar pretty.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 Documentation/admin-guide/hw-vuln/srso.rst | 71 ++++++++++++++--------
 1 file changed, 44 insertions(+), 27 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index 32eb5e6db272..af59a9395662 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -42,42 +42,59 @@ The sysfs file showing SRSO mitigation status is:
 
 The possible values in this file are:
 
- - 'Not affected'               The processor is not vulnerable
+ * 'Not affected':
 
- - 'Vulnerable: no microcode'   The processor is vulnerable, no
-                                microcode extending IBPB functionality
-                                to address the vulnerability has been
-                                applied.
+   The processor is not vulnerable
 
- - 'Mitigation: microcode'      Extended IBPB functionality microcode
-                                patch has been applied. It does not
-                                address User->Kernel and Guest->Host
-                                transitions protection but it does
-                                address User->User and VM->VM attack
-                                vectors.
+ * 'Vulnerable: no microcode':
 
-                                (spec_rstack_overflow=microcode)
+   The processor is vulnerable, no microcode extending IBPB
+   functionality to address the vulnerability has been applied.
 
- - 'Mitigation: safe RET'       Software-only mitigation. It complements
-                                the extended IBPB microcode patch
-                                functionality by addressing User->Kernel 
-                                and Guest->Host transitions protection.
+ * 'Mitigation: microcode':
 
-                                Selected by default or by
-                                spec_rstack_overflow=safe-ret
+   Extended IBPB functionality microcode patch has been applied. It does
+   not address User->Kernel and Guest->Host transitions protection but it
+   does address User->User and VM->VM attack vectors.
 
- - 'Mitigation: IBPB'           Similar protection as "safe RET" above
-                                but employs an IBPB barrier on privilege
-                                domain crossings (User->Kernel,
-                                Guest->Host).
+   Note that User->User mitigation is controlled by how the IBPB aspect in
+   the Spectre v2 mitigation is selected:
 
-                                (spec_rstack_overflow=ibpb)
+    * conditional IBPB:
+
+      where each process can select whether it needs an IBPB issued
+      around it PR_SPEC_DISABLE/_ENABLE etc, see :doc:`spectre`
+
+    * strict:
+
+      i.e., always on - by supplying spectre_v2_user=on on the kernel
+      command line
+
+   (spec_rstack_overflow=microcode)
+
+ * 'Mitigation: safe RET':
+
+   Software-only mitigation. It complements the extended IBPB microcode
+   patch functionality by addressing User->Kernel and Guest->Host
+   transitions protection.
+
+   Selected by default or by spec_rstack_overflow=safe-ret
+
+ * 'Mitigation: IBPB':
+
+   Similar protection as "safe RET" above but employs an IBPB barrier on
+   privilege domain crossings (User->Kernel, Guest->Host).
+
+  (spec_rstack_overflow=ibpb)
+
+ * 'Mitigation: IBPB on VMEXIT':
+
+   Mitigation addressing the cloud provider scenario - the Guest->Host
+   transitions only.
+
+   (spec_rstack_overflow=ibpb-vmexit)
 
- - 'Mitigation: IBPB on VMEXIT' Mitigation addressing the cloud provider
-                                scenario - the Guest->Host transitions
-                                only.
 
-                                (spec_rstack_overflow=ibpb-vmexit)
 
 In order to exploit vulnerability, an attacker needs to:
 
-- 
2.41.0

Re: [PATCH 3/3] Documentation/srso: Document IBPB aspect and fix formatting

[Pawan Gupta]

On Wed, Aug 09, 2023 at 12:27:00PM +0200, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> Add a note about the dependency of the User->User mitigation on the
> previous Spectre v2 IBPB selection.
> 
> Make the layout moar pretty.
> 
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> ---
>  Documentation/admin-guide/hw-vuln/srso.rst | 71 ++++++++++++++--------
>  1 file changed, 44 insertions(+), 27 deletions(-)
> 
> diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
> index 32eb5e6db272..af59a9395662 100644
> --- a/Documentation/admin-guide/hw-vuln/srso.rst
> +++ b/Documentation/admin-guide/hw-vuln/srso.rst
> @@ -42,42 +42,59 @@ The sysfs file showing SRSO mitigation status is:
>  
>  The possible values in this file are:
>  
> - - 'Not affected'               The processor is not vulnerable
> + * 'Not affected':
>  
> - - 'Vulnerable: no microcode'   The processor is vulnerable, no
> -                                microcode extending IBPB functionality
> -                                to address the vulnerability has been
> -                                applied.
> +   The processor is not vulnerable
>  
> - - 'Mitigation: microcode'      Extended IBPB functionality microcode
> -                                patch has been applied. It does not
> -                                address User->Kernel and Guest->Host
> -                                transitions protection but it does
> -                                address User->User and VM->VM attack
> -                                vectors.
> + * 'Vulnerable: no microcode':

All other mitigations capitalizes the first letter, to be consistent
s/no microcode/No microcode/

> -                                (spec_rstack_overflow=microcode)
> +   The processor is vulnerable, no microcode extending IBPB
> +   functionality to address the vulnerability has been applied.
>  
> - - 'Mitigation: safe RET'       Software-only mitigation. It complements
> -                                the extended IBPB microcode patch
> -                                functionality by addressing User->Kernel 
> -                                and Guest->Host transitions protection.
> + * 'Mitigation: microcode':

Ditto.

[tip: x86/bugs] Documentation/srso: Document IBPB aspect and fix formatting

[tip-bot2 for Borislav Petkov (AMD)]

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

Commit-ID:     09f9f37c324d90102e8574856ab168c34de1916d
Gitweb:        https://git.kernel.org/tip/09f9f37c324d90102e8574856ab168c34de1916d
Author:        Borislav Petkov (AMD) <bp@alien8.de>
AuthorDate:    Wed, 02 Aug 2023 20:07:32 +02:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Thu, 10 Aug 2023 11:03:12 +02:00

Documentation/srso: Document IBPB aspect and fix formatting

Add a note about the dependency of the User->User mitigation on the
previous Spectre v2 IBPB selection.

Make the layout moar pretty.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230809102700.29449-4-bp@alien8.de
---
 Documentation/admin-guide/hw-vuln/srso.rst | 71 +++++++++++++--------
 1 file changed, 44 insertions(+), 27 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index 32eb5e6..af59a93 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -42,42 +42,59 @@ The sysfs file showing SRSO mitigation status is:
 
 The possible values in this file are:
 
- - 'Not affected'               The processor is not vulnerable
+ * 'Not affected':
 
- - 'Vulnerable: no microcode'   The processor is vulnerable, no
-                                microcode extending IBPB functionality
-                                to address the vulnerability has been
-                                applied.
+   The processor is not vulnerable
 
- - 'Mitigation: microcode'      Extended IBPB functionality microcode
-                                patch has been applied. It does not
-                                address User->Kernel and Guest->Host
-                                transitions protection but it does
-                                address User->User and VM->VM attack
-                                vectors.
+ * 'Vulnerable: no microcode':
 
-                                (spec_rstack_overflow=microcode)
+   The processor is vulnerable, no microcode extending IBPB
+   functionality to address the vulnerability has been applied.
 
- - 'Mitigation: safe RET'       Software-only mitigation. It complements
-                                the extended IBPB microcode patch
-                                functionality by addressing User->Kernel 
-                                and Guest->Host transitions protection.
+ * 'Mitigation: microcode':
 
-                                Selected by default or by
-                                spec_rstack_overflow=safe-ret
+   Extended IBPB functionality microcode patch has been applied. It does
+   not address User->Kernel and Guest->Host transitions protection but it
+   does address User->User and VM->VM attack vectors.
 
- - 'Mitigation: IBPB'           Similar protection as "safe RET" above
-                                but employs an IBPB barrier on privilege
-                                domain crossings (User->Kernel,
-                                Guest->Host).
+   Note that User->User mitigation is controlled by how the IBPB aspect in
+   the Spectre v2 mitigation is selected:
 
-                                (spec_rstack_overflow=ibpb)
+    * conditional IBPB:
+
+      where each process can select whether it needs an IBPB issued
+      around it PR_SPEC_DISABLE/_ENABLE etc, see :doc:`spectre`
+
+    * strict:
+
+      i.e., always on - by supplying spectre_v2_user=on on the kernel
+      command line
+
+   (spec_rstack_overflow=microcode)
+
+ * 'Mitigation: safe RET':
+
+   Software-only mitigation. It complements the extended IBPB microcode
+   patch functionality by addressing User->Kernel and Guest->Host
+   transitions protection.
+
+   Selected by default or by spec_rstack_overflow=safe-ret
+
+ * 'Mitigation: IBPB':
+
+   Similar protection as "safe RET" above but employs an IBPB barrier on
+   privilege domain crossings (User->Kernel, Guest->Host).
+
+  (spec_rstack_overflow=ibpb)
+
+ * 'Mitigation: IBPB on VMEXIT':
+
+   Mitigation addressing the cloud provider scenario - the Guest->Host
+   transitions only.
+
+   (spec_rstack_overflow=ibpb-vmexit)
 
- - 'Mitigation: IBPB on VMEXIT' Mitigation addressing the cloud provider
-                                scenario - the Guest->Host transitions
-                                only.
 
-                                (spec_rstack_overflow=ibpb-vmexit)
 
 In order to exploit vulnerability, an attacker needs to:
 

Re: [PATCH 0/3] x86/bugs: Some SRSO fixes

[Greg Kroah-Hartman]

On Wed, Aug 09, 2023 at 12:26:57PM +0200, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> 
> Hi all,
> 
> those are the leftover smaller fixes which can go after the release
> date. I'll queue them next week.
> 
> Thx.
> 
> Borislav Petkov (AMD) (3):
>   Documentation/hw-vuln: Unify filename specification in index
>   driver core: cpu: Unify redundant silly stubs
>   Documentation/srso: Document IBPB aspect and fix formatting
> 
>  Documentation/admin-guide/hw-vuln/index.rst | 12 +--
>  Documentation/admin-guide/hw-vuln/srso.rst  | 71 ++++++++++-------
>  drivers/base/cpu.c                          | 86 +++++----------------
>  3 files changed, 68 insertions(+), 101 deletions(-)
> 
> -- 
> 2.41.0
> 

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>