Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Rafael J. Wysocki]

On Friday, July 19, 2013 11:08:49 AM Tim Chen wrote:
> On Fri, 2013-07-19 at 16:49 +0200, Rafael J. Wysocki wrote:
> > > > > > This should cause udev to load the crct10dif_pclml module when cpu
> > > > > > support the PCLMULQDQ (feature code 0081).  I did my testing during
> > > > > > development on 3.10 and the module was indeed loaded.
> > > > > >
> > > > > > However, I found that the following commit under 3.11-rc1 broke
> > > > > > the mechanism after some bisection.
> > > > > >
> > > > > > commit ac212b6980d8d5eda705864fc5a8ecddc6d6eacc
> > > > > > Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > > > > > Date:   Fri May 3 00:26:22 2013 +0200
> > > > > >
> > > > > >      ACPI / processor: Use common hotplug infrastructure
> > > > > >      
> > > > > >      Split the ACPI processor driver into two parts, one that is
> > > > > >      non-modular, resides in the ACPI core and handles the enumeration
> > > > > >      and hotplug of processors and one that implements the rest of the
> > > > > >      existing processor driver functionality.
> > > > > >      
> > > > > > Rafael, can you check and see if this can be fixed so those optimized
> > > > > > crypto modules for Intel cpu that support them can be loaded?
> > > > > 
> > > > > I think this is an ordering issue between udev startup and the time when 
> > > > > devices are registered.
> > > > 
> > > > Something that can be fixed?
> > > 
> > > I'm sure it can be fixes, but I'm not sure whether it's a udev bug or real
> > > breakage in the kernel yet.  I need to figure out that part.
> > 
> > OK
> > 
> > I wonder if the appended patch makes the issue go away for you?
> > 
> 
> Rafael, the patch did fix the cpu feature based module loading issue.
> Thanks for your quick response.

Alas, this is not the one I'd like to apply.

With that patch applied, new device objects are created to avoid binding the
processor driver directly to the cpu system device objects, because that
apparently confuses udev and it starts to ignore the cpu modalias once the
driver has been bound to any of those objects.

I've verified in the meantime that this indeed is the case.

A link to the patch in question: https://patchwork.kernel.org/patch/2830561/

Greg, I asked you some time ago whether or not it was possible for udev to stop
autoloading modules that matched the cpu modalias after a driver had been bound
to the cpu system device objects and you said "no".  However, this time I can
say with certainty that that really is the case.  So, the question now is
whether or not we can do anything in the kernel to avoid that confusion in udev
instead of applying the patch linked above (which is beyond ugly in my not so
humble opinion)?

Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Greg Kroah-Hartman]

On Fri, Jul 19, 2013 at 11:38:04PM +0200, Rafael J. Wysocki wrote:
> Alas, this is not the one I'd like to apply.
> 
> With that patch applied, new device objects are created to avoid binding the
> processor driver directly to the cpu system device objects, because that
> apparently confuses udev and it starts to ignore the cpu modalias once the
> driver has been bound to any of those objects.
> 
> I've verified in the meantime that this indeed is the case.
> 
> A link to the patch in question: https://patchwork.kernel.org/patch/2830561/
> 
> Greg, I asked you some time ago whether or not it was possible for udev to stop
> autoloading modules that matched the cpu modalias after a driver had been bound
> to the cpu system device objects and you said "no".  However, this time I can
> say with certainty that that really is the case.  So, the question now is
> whether or not we can do anything in the kernel to avoid that confusion in udev
> instead of applying the patch linked above (which is beyond ugly in my not so
> humble opinion)?

udev isn't doing any module loading, 'modprobe' is just being called for
any new module alias that shows up in the system, and all of the drivers
that match it then get loaded.

How is it a problem if a module is attempted to be loaded that is
already loaded?  How is it a problem if a different module is loaded for
a device already bound to a driver?  Both of those should be total
"no-ops" for the kernel.

But, I don't know anything about the cpu code, how is loading a module
causing problems?  That sounds like it needs to be fixes, as any root
user can load modules whenever they want, you can't protect the kernel
from doing that.

thanks,

greg k-h

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[H. Peter Anvin]

On 07/19/2013 04:16 PM, Greg Kroah-Hartman wrote:
> 
> udev isn't doing any module loading, 'modprobe' is just being called for
> any new module alias that shows up in the system, and all of the drivers
> that match it then get loaded.
> 
> How is it a problem if a module is attempted to be loaded that is
> already loaded?  How is it a problem if a different module is loaded for
> a device already bound to a driver?  Both of those should be total
> "no-ops" for the kernel.
> 
> But, I don't know anything about the cpu code, how is loading a module
> causing problems?  That sounds like it needs to be fixes, as any root
> user can load modules whenever they want, you can't protect the kernel
> from doing that.
> 

The issue here seems to be the dynamic binding nature of the crypto
subsystem.  When something needs crypto, it will request the appropriate
crypto module (e.g. crct10dif), which may race with detecting a specific
hardware accelerator based on CPUID or device information (e.g.
crct10dif_pclmul).

RAID has effectively the same issue, and we just "solved" it by
compiling in all the accelerators into the top-level module.

	-hpa

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Herbert Xu]

On Fri, Jul 19, 2013 at 04:21:09PM -0700, H. Peter Anvin wrote:
>
> The issue here seems to be the dynamic binding nature of the crypto
> subsystem.  When something needs crypto, it will request the appropriate
> crypto module (e.g. crct10dif), which may race with detecting a specific
> hardware accelerator based on CPUID or device information (e.g.
> crct10dif_pclmul).
> 
> RAID has effectively the same issue, and we just "solved" it by
> compiling in all the accelerators into the top-level module.

I think for crypto the simplest solution is to not do CPUID-based
loading.  Then crypto users will simply load the module alias which
causes modprobe to load all modules providing that alias.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Greg Kroah-Hartman]

On Fri, Jul 19, 2013 at 04:21:09PM -0700, H. Peter Anvin wrote:
> On 07/19/2013 04:16 PM, Greg Kroah-Hartman wrote:
> > 
> > udev isn't doing any module loading, 'modprobe' is just being called for
> > any new module alias that shows up in the system, and all of the drivers
> > that match it then get loaded.
> > 
> > How is it a problem if a module is attempted to be loaded that is
> > already loaded?  How is it a problem if a different module is loaded for
> > a device already bound to a driver?  Both of those should be total
> > "no-ops" for the kernel.
> > 
> > But, I don't know anything about the cpu code, how is loading a module
> > causing problems?  That sounds like it needs to be fixes, as any root
> > user can load modules whenever they want, you can't protect the kernel
> > from doing that.
> > 
> 
> The issue here seems to be the dynamic binding nature of the crypto
> subsystem.  When something needs crypto, it will request the appropriate
> crypto module (e.g. crct10dif), which may race with detecting a specific
> hardware accelerator based on CPUID or device information (e.g.
> crct10dif_pclmul).
> 
> RAID has effectively the same issue, and we just "solved" it by
> compiling in all the accelerators into the top-level module.

Then there's nothing to be done in udev or kmod, right?

greg k-h

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[H. Peter Anvin]

On 07/19/2013 04:26 PM, Greg Kroah-Hartman wrote:
>>
>> RAID has effectively the same issue, and we just "solved" it by
>> compiling in all the accelerators into the top-level module.
> 
> Then there's nothing to be done in udev or kmod, right?
> 

I don't know.

	-hpa

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Tim Chen]

On Sat, 2013-07-20 at 09:24 +1000, Herbert Xu wrote:
> On Fri, Jul 19, 2013 at 04:21:09PM -0700, H. Peter Anvin wrote:
> >
> > The issue here seems to be the dynamic binding nature of the crypto
> > subsystem.  When something needs crypto, it will request the appropriate
> > crypto module (e.g. crct10dif), which may race with detecting a specific
> > hardware accelerator based on CPUID or device information (e.g.
> > crct10dif_pclmul).
> > 
> > RAID has effectively the same issue, and we just "solved" it by
> > compiling in all the accelerators into the top-level module.
> 
> I think for crypto the simplest solution is to not do CPUID-based
> loading.  Then crypto users will simply load the module alias which
> causes modprobe to load all modules providing that alias.
> 
> Cheers,

Herbert,

I've tried the module alias approach (see my earlier mail with patch) 
but it didn't seem to load things properly.  Can you check to see if 
there's anything I did incorrectly.

Tim

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Rafael J. Wysocki]

On Friday, July 19, 2013 04:16:30 PM Greg Kroah-Hartman wrote:
> On Fri, Jul 19, 2013 at 11:38:04PM +0200, Rafael J. Wysocki wrote:
> > Alas, this is not the one I'd like to apply.
> > 
> > With that patch applied, new device objects are created to avoid binding the
> > processor driver directly to the cpu system device objects, because that
> > apparently confuses udev and it starts to ignore the cpu modalias once the
> > driver has been bound to any of those objects.
> > 
> > I've verified in the meantime that this indeed is the case.
> > 
> > A link to the patch in question: https://patchwork.kernel.org/patch/2830561/
> > 
> > Greg, I asked you some time ago whether or not it was possible for udev to stop
> > autoloading modules that matched the cpu modalias after a driver had been bound
> > to the cpu system device objects and you said "no".  However, this time I can
> > say with certainty that that really is the case.  So, the question now is
> > whether or not we can do anything in the kernel to avoid that confusion in udev
> > instead of applying the patch linked above (which is beyond ugly in my not so
> > humble opinion)?
> 
> udev isn't doing any module loading, 'modprobe' is just being called for
> any new module alias that shows up in the system, and all of the drivers
> that match it then get loaded.

The problem is that that doesn't happen when a driver is bound to the
cpu system device objects.  modprobe is just not called for modules that
match the cpu modalias in that case.

If I call modprobe manually for any of the modules in question, it loads
and works no problem.

> How is it a problem if a module is attempted to be loaded that is
> already loaded?  How is it a problem if a different module is loaded for
> a device already bound to a driver?  Both of those should be total
> "no-ops" for the kernel.

Precisely, but that's not what happens in practice, hence my question.

The situation is this:

- With 3.11-rc1 modules that match the CPU modalias are not loaded
  automatically (that is, modprobe is not called for them by udev) after
  the processor module is loaded.
- With 3.10 they are loaded automatically at any time.
- With the patch at https://patchwork.kernel.org/patch/2830561/ on top of
  3.11-rc1 the situation is the same as for 3.10.

Therefore we have a kernel regression from 3.10 (with respect to the existing
user space which is udev) in 3.11-rc1 3.10 and the patch at
https://patchwork.kernel.org/patch/2830561/ makes that regression go away.

However, that patch is totally voodoo programming, so I wonder if there is any
saner alternative or we really need to do voodoo programming in the kernel to
work around udev's confusion.

> But, I don't know anything about the cpu code, how is loading a module
> causing problems?  That sounds like it needs to be fixes, as any root
> user can load modules whenever they want, you can't protect the kernel
> from doing that.

Yes, that needs to be fixed, but I don't know *why* it is a problem in the
first place.  I'd like to understand what's going on, because I don't
right now.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Tim Chen]

On Fri, 2013-07-19 at 16:37 -0700, Tim Chen wrote:
> On Sat, 2013-07-20 at 09:24 +1000, Herbert Xu wrote:
> > On Fri, Jul 19, 2013 at 04:21:09PM -0700, H. Peter Anvin wrote:
> > >
> > > The issue here seems to be the dynamic binding nature of the crypto
> > > subsystem.  When something needs crypto, it will request the appropriate
> > > crypto module (e.g. crct10dif), which may race with detecting a specific
> > > hardware accelerator based on CPUID or device information (e.g.
> > > crct10dif_pclmul).
> > > 
> > > RAID has effectively the same issue, and we just "solved" it by
> > > compiling in all the accelerators into the top-level module.
> > 
> > I think for crypto the simplest solution is to not do CPUID-based
> > loading.  Then crypto users will simply load the module alias which
> > causes modprobe to load all modules providing that alias.
> > 
> > Cheers,
> 
> Herbert,
> 
> I've tried the module alias approach (see my earlier mail with patch) 
> but it didn't seem to load things properly.  Can you check to see if 
> there's anything I did incorrectly.
> 
> Tim

I fixed a missing request_module statement in crct10dif library.  
So now things work if I have the following config:

CONFIG_CRYPTO_CRCT10DIF=m
CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m
CONFIG_CRC_T10DIF=m

However, when I have the library and generic algorithm compiled in,
I do not see the PCLMULQDQ version loaded.

CONFIG_CRYPTO_CRCT10DIF=y
CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m
CONFIG_CRC_T10DIF=y

Perhaps I am initiating the crct10dif library at a really early
stage when things are compiled in, where the module is not in 
initramfs?  In that case, perhaps we should only allow 
PCLMUL version to be compiled in
and not exist as a module?

Here's the patch I tried:

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
 arch/x86/crypto/crct10dif-pclmul_glue.c     | 8 +-------
 crypto/Makefile                             | 2 +-
 crypto/{crct10dif.c => crct10dif_generic.c} | 1 +
 lib/crc-t10dif.c                            | 1 +
 4 files changed, 4 insertions(+), 8 deletions(-)
 rename crypto/{crct10dif.c => crct10dif_generic.c} (99%)

diff --git a/arch/x86/crypto/crct10dif-pclmul_glue.c b/arch/x86/crypto/crct10dif-pclmul_glue.c
index 7845d7f..7ad5f09 100644
--- a/arch/x86/crypto/crct10dif-pclmul_glue.c
+++ b/arch/x86/crypto/crct10dif-pclmul_glue.c
@@ -121,15 +121,9 @@ static struct shash_alg alg = {
 	}
 };
 
-static const struct x86_cpu_id crct10dif_cpu_id[] = {
-	X86_FEATURE_MATCH(X86_FEATURE_PCLMULQDQ),
-	{}
-};
-MODULE_DEVICE_TABLE(x86cpu, crct10dif_cpu_id);
-
 static int __init crct10dif_intel_mod_init(void)
 {
-	if (!x86_match_cpu(crct10dif_cpu_id))
+	if (!cpu_has_pclmulqdq)
 		return -ENODEV;
 
 	return crypto_register_shash(&alg);
diff --git a/crypto/Makefile b/crypto/Makefile
index 2d5ed08..3fd76fa 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -83,7 +83,7 @@ obj-$(CONFIG_CRYPTO_ZLIB) += zlib.o
 obj-$(CONFIG_CRYPTO_MICHAEL_MIC) += michael_mic.o
 obj-$(CONFIG_CRYPTO_CRC32C) += crc32c.o
 obj-$(CONFIG_CRYPTO_CRC32) += crc32.o
-obj-$(CONFIG_CRYPTO_CRCT10DIF) += crct10dif.o
+obj-$(CONFIG_CRYPTO_CRCT10DIF) += crct10dif_generic.o
 obj-$(CONFIG_CRYPTO_AUTHENC) += authenc.o authencesn.o
 obj-$(CONFIG_CRYPTO_LZO) += lzo.o
 obj-$(CONFIG_CRYPTO_LZ4) += lz4.o
diff --git a/crypto/crct10dif.c b/crypto/crct10dif_generic.c
similarity index 99%
rename from crypto/crct10dif.c
rename to crypto/crct10dif_generic.c
index 92aca96..c960a95 100644
--- a/crypto/crct10dif.c
+++ b/crypto/crct10dif_generic.c
@@ -176,3 +176,4 @@ module_exit(crct10dif_mod_fini);
 MODULE_AUTHOR("Tim Chen <tim.c.chen@linux.intel.com>");
 MODULE_DESCRIPTION("T10 DIF CRC calculation.");
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("crct10dif");
diff --git a/lib/crc-t10dif.c b/lib/crc-t10dif.c
index fe3428c..d8cd353 100644
--- a/lib/crc-t10dif.c
+++ b/lib/crc-t10dif.c
@@ -38,6 +38,7 @@ EXPORT_SYMBOL(crc_t10dif);
 
 static int __init crc_t10dif_mod_init(void)
 {
+	request_module("crct10dif");
 	crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
 	return PTR_RET(crct10dif_tfm);
 }
-- 
1.7.11.7

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to moduledependency.

[Tetsuo Handa]

Tim Chen wrote:
> On Fri, 2013-07-19 at 16:37 -0700, Tim Chen wrote:
> > Herbert,
> > 
> > I've tried the module alias approach (see my earlier mail with patch) 
> > but it didn't seem to load things properly.  Can you check to see if 
> > there's anything I did incorrectly.
> > 
> > Tim
> 
> I fixed a missing request_module statement in crct10dif library.  
> So now things work if I have the following config:
> 
> CONFIG_CRYPTO_CRCT10DIF=m
> CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m
> CONFIG_CRC_T10DIF=m
> 
> However, when I have the library and generic algorithm compiled in,
> I do not see the PCLMULQDQ version loaded.
> 
> CONFIG_CRYPTO_CRCT10DIF=y
> CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m
> CONFIG_CRC_T10DIF=y
> 
> Perhaps I am initiating the crct10dif library at a really early
> stage when things are compiled in, where the module is not in 
> initramfs?  In that case, perhaps we should only allow 
> PCLMUL version to be compiled in
> and not exist as a module?

I think that use of request_module("crct10dif") does not help loading
crct10dif-pclmul.ko when CONFIG_CRC_T10DIF=y CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m ,
for there is no / directory (note that the initramfs is not yet mounted as /
for loading modules which are not in vmlinux) when any module_init() functions
which are in vmlinux are called.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Rafael J. Wysocki]

On Saturday, July 20, 2013 02:00:44 AM Rafael J. Wysocki wrote:
> On Friday, July 19, 2013 04:16:30 PM Greg Kroah-Hartman wrote:
> > On Fri, Jul 19, 2013 at 11:38:04PM +0200, Rafael J. Wysocki wrote:
> > > Alas, this is not the one I'd like to apply.
> > > 
> > > With that patch applied, new device objects are created to avoid binding the
> > > processor driver directly to the cpu system device objects, because that
> > > apparently confuses udev and it starts to ignore the cpu modalias once the
> > > driver has been bound to any of those objects.
> > > 
> > > I've verified in the meantime that this indeed is the case.
> > > 
> > > A link to the patch in question: https://patchwork.kernel.org/patch/2830561/
> > > 
> > > Greg, I asked you some time ago whether or not it was possible for udev to stop
> > > autoloading modules that matched the cpu modalias after a driver had been bound
> > > to the cpu system device objects and you said "no".  However, this time I can
> > > say with certainty that that really is the case.  So, the question now is
> > > whether or not we can do anything in the kernel to avoid that confusion in udev
> > > instead of applying the patch linked above (which is beyond ugly in my not so
> > > humble opinion)?
> > 
> > udev isn't doing any module loading, 'modprobe' is just being called for
> > any new module alias that shows up in the system, and all of the drivers
> > that match it then get loaded.
> 
> The problem is that that doesn't happen when a driver is bound to the
> cpu system device objects.  modprobe is just not called for modules that
> match the cpu modalias in that case.
> 
> If I call modprobe manually for any of the modules in question, it loads
> and works no problem.

OK, I know what's up.  udev has no rule that would allow it to load stuff on
the basis of MODALIAS if DRIVER is set in the event properties.

So, the following rule needs to be added to udev rules for things to work
as before:

DRIVER=="processor", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

To be precise, I added a file called 80-drivers.rules to /etc/udev/rules.d/
with the following contents:

ACTION=="remove", GOTO="drivers_end"

DRIVER=="processor", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

LABEL="drivers_end"

but I'm not sure how to propagate this to the udev maintainers.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Herbert Xu]

On Fri, Jul 19, 2013 at 06:31:04PM -0700, Tim Chen wrote:
>
> However, when I have the library and generic algorithm compiled in,
> I do not see the PCLMULQDQ version loaded.
> 
> CONFIG_CRYPTO_CRCT10DIF=y
> CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m
> CONFIG_CRC_T10DIF=y

That is completely expected.  I don't really think we need to
do anything about this case.  After all, if the admin wants to
use the optimised version for CRC_T10DIF then they could simply
compile that in as well.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to moduledependency.

[Tetsuo Handa]

Herbert Xu wrote:
> On Fri, Jul 19, 2013 at 06:31:04PM -0700, Tim Chen wrote:
> >
> > However, when I have the library and generic algorithm compiled in,
> > I do not see the PCLMULQDQ version loaded.
> > 
> > CONFIG_CRYPTO_CRCT10DIF=y
> > CONFIG_CRYPTO_CRCT10DIF_PCLMUL=m
> > CONFIG_CRC_T10DIF=y
> 
> That is completely expected.  I don't really think we need to
> do anything about this case.  After all, if the admin wants to
> use the optimised version for CRC_T10DIF then they could simply
> compile that in as well.
> 

Wow! ;-)

But I'd expect something like

 static int __init crc_t10dif_mod_init(void)
 {
+#if !defined(CONFIG_CRC_T10DIF_MODULE) && defined(CONFIG_CRYPTO_CRCT10DIF_PCLMUL_MODULE)
+	printk(KERN_WARNING "Consider CONFIG_CRYPTO_CRCT10DIF_PCLMUL=y for better performance\n");
+#endif
 	crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
 	return PTR_RET(crct10dif_tfm);
 }

because the admin might not be aware of this implication.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Rafael J. Wysocki]

On Saturday, July 20, 2013 05:06:29 AM Rafael J. Wysocki wrote:
> On Saturday, July 20, 2013 02:00:44 AM Rafael J. Wysocki wrote:
> > On Friday, July 19, 2013 04:16:30 PM Greg Kroah-Hartman wrote:
> > > On Fri, Jul 19, 2013 at 11:38:04PM +0200, Rafael J. Wysocki wrote:
> > > > Alas, this is not the one I'd like to apply.
> > > > 
> > > > With that patch applied, new device objects are created to avoid binding the
> > > > processor driver directly to the cpu system device objects, because that
> > > > apparently confuses udev and it starts to ignore the cpu modalias once the
> > > > driver has been bound to any of those objects.
> > > > 
> > > > I've verified in the meantime that this indeed is the case.
> > > > 
> > > > A link to the patch in question: https://patchwork.kernel.org/patch/2830561/
> > > > 
> > > > Greg, I asked you some time ago whether or not it was possible for udev to stop
> > > > autoloading modules that matched the cpu modalias after a driver had been bound
> > > > to the cpu system device objects and you said "no".  However, this time I can
> > > > say with certainty that that really is the case.  So, the question now is
> > > > whether or not we can do anything in the kernel to avoid that confusion in udev
> > > > instead of applying the patch linked above (which is beyond ugly in my not so
> > > > humble opinion)?
> > > 
> > > udev isn't doing any module loading, 'modprobe' is just being called for
> > > any new module alias that shows up in the system, and all of the drivers
> > > that match it then get loaded.
> > 
> > The problem is that that doesn't happen when a driver is bound to the
> > cpu system device objects.  modprobe is just not called for modules that
> > match the cpu modalias in that case.
> > 
> > If I call modprobe manually for any of the modules in question, it loads
> > and works no problem.
> 
> OK, I know what's up.  udev has no rule that would allow it to load stuff on
> the basis of MODALIAS if DRIVER is set in the event properties.
> 
> So, the following rule needs to be added to udev rules for things to work
> as before:
> 
> DRIVER=="processor", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"
> 
> To be precise, I added a file called 80-drivers.rules to /etc/udev/rules.d/

Well, that wasn't a good idea, because the original 80-drivers.rules didn't
work then, but I renamed the new file (in /etc/udev/rules.d/) to 80-cpu.rules
and put this line (alone) into it:

ACTION="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

After that change everything works happily again.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 3.11-rc1] crypto: Fix boot failure due to module dependency.

[Rafael J. Wysocki]

On Saturday, July 20, 2013 11:51:55 AM Rafael J. Wysocki wrote:
> On Saturday, July 20, 2013 05:06:29 AM Rafael J. Wysocki wrote:
> > On Saturday, July 20, 2013 02:00:44 AM Rafael J. Wysocki wrote:
> > > On Friday, July 19, 2013 04:16:30 PM Greg Kroah-Hartman wrote:
> > > > On Fri, Jul 19, 2013 at 11:38:04PM +0200, Rafael J. Wysocki wrote:
> > > > > Alas, this is not the one I'd like to apply.
> > > > > 
> > > > > With that patch applied, new device objects are created to avoid binding the
> > > > > processor driver directly to the cpu system device objects, because that
> > > > > apparently confuses udev and it starts to ignore the cpu modalias once the
> > > > > driver has been bound to any of those objects.
> > > > > 
> > > > > I've verified in the meantime that this indeed is the case.
> > > > > 
> > > > > A link to the patch in question: https://patchwork.kernel.org/patch/2830561/
> > > > > 
> > > > > Greg, I asked you some time ago whether or not it was possible for udev to stop
> > > > > autoloading modules that matched the cpu modalias after a driver had been bound
> > > > > to the cpu system device objects and you said "no".  However, this time I can
> > > > > say with certainty that that really is the case.  So, the question now is
> > > > > whether or not we can do anything in the kernel to avoid that confusion in udev
> > > > > instead of applying the patch linked above (which is beyond ugly in my not so
> > > > > humble opinion)?
> > > > 
> > > > udev isn't doing any module loading, 'modprobe' is just being called for
> > > > any new module alias that shows up in the system, and all of the drivers
> > > > that match it then get loaded.
> > > 
> > > The problem is that that doesn't happen when a driver is bound to the
> > > cpu system device objects.  modprobe is just not called for modules that
> > > match the cpu modalias in that case.
> > > 
> > > If I call modprobe manually for any of the modules in question, it loads
> > > and works no problem.
> > 
> > OK, I know what's up.  udev has no rule that would allow it to load stuff on
> > the basis of MODALIAS if DRIVER is set in the event properties.
> > 
> > So, the following rule needs to be added to udev rules for things to work
> > as before:
> > 
> > DRIVER=="processor", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"
> > 
> > To be precise, I added a file called 80-drivers.rules to /etc/udev/rules.d/
> 
> Well, that wasn't a good idea, because the original 80-drivers.rules didn't
> work then, but I renamed the new file (in /etc/udev/rules.d/) to 80-cpu.rules
> and put this line (alone) into it:
> 
> ACTION="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

I made a mistake in the above, which should be:

ACTION=="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}"

sorry about that.

> After that change everything works happily again.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.