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s390: Autoload uvdevice module based on CPU feature

PATCH In review Steffen Eiden 3 participants 6 messages Jul 1, 2022 – Jul 4, 2022

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Steffen Eiden

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#0 lore raw

cover s390: Autoload uvdevice module based on CPU feature

Currently, the uvdevice (drivers/s390/char/uvdevice) must be loaded manually. We can, however, determine if the Ultravisor is available by observing facility 158.

This series, first, introduces the HWCAP_UV connected to facility 158. And, second, it automatically loads the uvdevice if HWCAP_UV is present.

Steffen Eiden (2):
s390/hwcaps: Add HWCAP_UV
drivers/s390/char/uvdevice: Autoload module based on CPU feature

 arch/s390/include/asm/elf.h  | 2 ++
 arch/s390/kernel/processor.c | 5 +++++
 drivers/s390/char/uvdevice.c | 5 ++---
 3 files changed, 9 insertions(+), 3 deletions(-)
Signature · 1 line
2.35.3
author
#1 lore raw

PATCH 1/2 s390/hwcaps: Add HWCAP_UV

This patch adds a hardware capability for the Ultravisor. This capability will be present if facility 158 is enabled.

Signed-off-by Steffen Eiden <[email protected]>
---
 arch/s390/include/asm/elf.h  | 2 ++
 arch/s390/kernel/processor.c | 5 +++++
 2 files changed, 7 insertions(+)
arch/s390/include/asm/elf.h +2 -0
index 70a30ae258b7..3a5e89ce4fd0 100644
@@ -115,6 +115,7 @@ enum {
 	HWCAP_NR_NNPA		= 20,
 	HWCAP_NR_PCI_MIO	= 21,
 	HWCAP_NR_SIE		= 22,
+	HWCAP_NR_UV		= 23,
 	HWCAP_NR_MAX
 };
 

@@ -142,6 +143,7 @@ enum {
 #define HWCAP_NNPA		BIT(HWCAP_NR_NNPA)
 #define HWCAP_PCI_MIO		BIT(HWCAP_NR_PCI_MIO)
 #define HWCAP_SIE		BIT(HWCAP_NR_SIE)
+#define HWCAP_UV		BIT(HWCAP_NR_UV)
 
 /*
  * These are used to set parameters in the core dumps.
arch/s390/kernel/processor.c +5 -0
index aa0e0e7fc773..80ccd57a2b00 100644
@@ -141,6 +141,7 @@ static void show_cpu_summary(struct seq_file *m, void *v)
 		[HWCAP_NR_NNPA]		= "nnpa",
 		[HWCAP_NR_PCI_MIO]	= "pcimio",
 		[HWCAP_NR_SIE]		= "sie",
+		[HWCAP_NR_UV]		= "uv",
 	};
 	int i, cpu;
 

@@ -249,6 +250,10 @@ static int __init setup_hwcaps(void)
 	if (sclp.has_sief2)
 		elf_hwcap |= HWCAP_SIE;
 
+	/* ultravisor-call (secure execution) */
+	if (test_facility(158))
+		elf_hwcap |= HWCAP_UV;
+
 	return 0;
 }
 arch_initcall(setup_hwcaps);
Signature · 1 line
2.35.3
maintainer
#2 lore raw

Re: [PATCH 1/2] s390/hwcaps: Add HWCAP_UV

Am 01.07.22 um 12:02 schrieb Steffen Eiden:

Quoted 14 lines

This patch adds a hardware capability for the Ultravisor. This capability will be present if facility 158 is enabled.

Signed-off-by Steffen Eiden <[email protected]>
---
  arch/s390/include/asm/elf.h  | 2 ++
  arch/s390/kernel/processor.c | 5 +++++
  2 files changed, 7 insertions(+)
arch/s390/include/asm/elf.h +0 -0
index 70a30ae258b7..3a5e89ce4fd0 100644

arch/s390/include/asm/elf.h enum { · line 120

Quoted 6 lines
arch/s390/include/asm/elf.h +1 -0
@@ -115,6 +115,7 @@ enum {
  	HWCAP_NR_NNPA		= 20,
  	HWCAP_NR_PCI_MIO	= 21,
  	HWCAP_NR_SIE		= 22,
+	HWCAP_NR_UV		= 23,
  	HWCAP_NR_MAX
  };

question for Heiko, Vasily, Alexander. This certainly works.
An alternative implementation would be to separate module_cpu_feature_match from HWCAP. (so uv would not be shown in /proc/cpuinfo and it would be seen in the aux vector). I would imagine that we might have more drivers in the future that depend on a facility but this facility is not really useful for userspace to know.

See arch/s390/include/asm/cpufeature.h
* Restrict the set of exposed CPU features to ELF hardware capabilities for
* now. Additional machine flags can be indicated by values larger than
* MAX_ELF_HWCAP_FEATURES.

Any preference from your side?

Quoted 32 lines
arch/s390/include/asm/elf.h +1 -0
@@ -142,6 +143,7 @@ enum {
  #define HWCAP_NNPA		BIT(HWCAP_NR_NNPA)
  #define HWCAP_PCI_MIO		BIT(HWCAP_NR_PCI_MIO)
  #define HWCAP_SIE		BIT(HWCAP_NR_SIE)
+#define HWCAP_UV		BIT(HWCAP_NR_UV)
 
  /*
   * These are used to set parameters in the core dumps.
arch/s390/kernel/processor.c +5 -0
index aa0e0e7fc773..80ccd57a2b00 100644
@@ -141,6 +141,7 @@ static void show_cpu_summary(struct seq_file *m, void *v)
  		[HWCAP_NR_NNPA]		= "nnpa",
  		[HWCAP_NR_PCI_MIO]	= "pcimio",
  		[HWCAP_NR_SIE]		= "sie",
+		[HWCAP_NR_UV]		= "uv",
  	};
  	int i, cpu;
 

@@ -249,6 +250,10 @@ static int __init setup_hwcaps(void)
  	if (sclp.has_sief2)
  		elf_hwcap |= HWCAP_SIE;
 
+	/* ultravisor-call (secure execution) */
+	if (test_facility(158))
+		elf_hwcap |= HWCAP_UV;
+
  	return 0;
  }
  arch_initcall(setup_hwcaps);
maintainer
#3 lore raw

Re: [PATCH 1/2] s390/hwcaps: Add HWCAP_UV

Quoted 29 lines · Christian Borntraeger

Am 01.07.22 um 12:02 schrieb Steffen Eiden:

Quoted 14 lines

This patch adds a hardware capability for the Ultravisor. This capability will be present if facility 158 is enabled.

Signed-off-by Steffen Eiden <[email protected]>
---
  arch/s390/include/asm/elf.h  | 2 ++
  arch/s390/kernel/processor.c | 5 +++++
  2 files changed, 7 insertions(+)
arch/s390/include/asm/elf.h +0 -0
index 70a30ae258b7..3a5e89ce4fd0 100644

arch/s390/include/asm/elf.h enum { · line 120

Quoted 6 lines
arch/s390/include/asm/elf.h +1 -0
@@ -115,6 +115,7 @@ enum {
  	HWCAP_NR_NNPA		= 20,
  	HWCAP_NR_PCI_MIO	= 21,
  	HWCAP_NR_SIE		= 22,
+	HWCAP_NR_UV		= 23,
  	HWCAP_NR_MAX
  };

question for Heiko, Vasily, Alexander. This certainly works.
An alternative implementation would be to separate module_cpu_feature_match from HWCAP. (so uv would not be shown in /proc/cpuinfo and it would be seen in the aux vector). I would imagine that we might have more drivers in the future that depend on a facility but this facility is not really useful for userspace to know.

Quoted 6 lines

See arch/s390/include/asm/cpufeature.h
* Restrict the set of exposed CPU features to ELF hardware capabilities for
* now. Additional machine flags can be indicated by values larger than
* MAX_ELF_HWCAP_FEATURES.

Any preference from your side?

I mentioned already before this RFC that my preferred solution would be to have a solution which extends the existing method to work (also) with facility bits - haven't checked if all existing users could be converted to facility bits, but making it more flexible would work certainly.

If Steffen is willing to do that, that would be very welcome. Otherwise I'll put that on my todo list.

author
#4 lore raw

Re: [PATCH 1/2] s390/hwcaps: Add HWCAP_UV

Quoted 1 line · Heiko Carstens

On Fri, Jul 01, 2022 at 12:10:18PM +0200, Christian Borntraeger wrote:

[ snip ]

Quoted 10 lines
Quoted 1 line

Any preference from your side?

I mentioned already before this RFC that my preferred solution would be to have a solution which extends the existing method to work (also) with facility bits - haven't checked if all existing users could be converted to facility bits, but making it more flexible would work certainly.

If Steffen is willing to do that, that would be very welcome. Otherwise I'll put that on my todo list.

I'll have a look on that.

author
#5 lore raw

PATCH 2/2 drivers/s390/char/uvdevice: Autoload module based on CPU feature

In reply to Steffen Eiden

With this patch the uvdevice will be automatically loaded when the HWCAP_UV bit is set.

Signed-off-by Steffen Eiden <[email protected]>
---
 drivers/s390/char/uvdevice.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)
drivers/s390/char/uvdevice.c +2 -3
index 66505d7166a6..fddbfc1e27a2 100644
@@ -27,6 +27,7 @@
 #include <linux/stddef.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
+#include <linux/cpufeature.h>
 
 #include <asm/uvdevice.h>
 #include <asm/uv.h>

@@ -244,12 +245,10 @@ static void __exit uvio_dev_exit(void)
 
 static int __init uvio_dev_init(void)
 {
-	if (!test_facility(158))
-		return -ENXIO;
 	return misc_register(&uvio_dev_miscdev);
 }
 
-module_init(uvio_dev_init);
+module_cpu_feature_match(UV, uvio_dev_init);
 module_exit(uvio_dev_exit);
 
 MODULE_AUTHOR("IBM Corporation");
Signature · 1 line
2.35.3