Isolate the SRCU functions and data structures within CONFIG_SRCU so that there
is a compile time failure if srcu is used when not enabled. This was decided to
be better than waiting until link time for a failure to occur.
There are places which include kvm headers and utilize kvm data structures
without checking if KVM is enabled. In two such archs(s390, ppc64), the current
patch makes the uses of KVM conditional on KVM being enabled. The other option,
which is to enable KVM unconditionally seemed a bit too much as we could easily
figure out KVM only parts and enclose them in ifdefs.
Signed-off-by: Pranith Kumar <[email protected]>
---
arch/powerpc/kernel/setup_64.c | 7 ++++++-
arch/s390/kernel/asm-offsets.c | 7 ++++++-
include/linux/notifier.h | 47 ++++++++++++++++++++++++------------------
include/linux/srcu.h | 6 +++++-
4 files changed, 44 insertions(+), 23 deletions(-)
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 4f3cfe1..f55302f 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -65,10 +65,13 @@
#include <asm/kexec.h>
#include <asm/mmu_context.h>
#include <asm/code-patching.h>
-#include <asm/kvm_ppc.h>
#include <asm/hugetlb.h>
#include <asm/epapr_hcalls.h>
+#if IS_ENABLED(CONFIG_KVM)
+#include <asm/kvm_ppc.h>
+#endif
+
#ifdef DEBUG
#define DBG(fmt...) udbg_printf(fmt)
#else
@@ -286,8 +289,10 @@ void __init early_setup(unsigned long dt_ptr)
*/
cpu_ready_for_interrupts();
+#if IS_ENABLED(CONFIG_KVM)
/* Reserve large chunks of memory for use by CMA for KVM */
kvm_cma_reserve();
+#endif
/*
* Reserve any gigantic pages requested on the command line.
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index ef279a1..2813a3c 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -7,12 +7,15 @@
#define ASM_OFFSETS_C
#include <linux/kbuild.h>
-#include <linux/kvm_host.h>
#include <linux/sched.h>
#include <asm/idle.h>
#include <asm/vdso.h>
#include <asm/pgtable.h>
+#if IS_ENABLED(CONFIG_KVM)
+#include <linux/kvm_host.h>
+#endif
+
/*
* Make sure that the compiler is new enough. We want a compiler that
* is known to work with the "Q" assembler constraint.
@@ -182,8 +185,10 @@ int main(void)
DEFINE(__LC_PGM_TDB, offsetof(struct _lowcore, pgm_tdb));
DEFINE(__THREAD_trap_tdb, offsetof(struct task_struct, thread.trap_tdb));
DEFINE(__GMAP_ASCE, offsetof(struct gmap, asce));
+#if IS_ENABLED(CONFIG_KVM)
DEFINE(__SIE_PROG0C, offsetof(struct kvm_s390_sie_block, prog0c));
DEFINE(__SIE_PROG20, offsetof(struct kvm_s390_sie_block, prog20));
+#endif /* CONFIG_KVM */
#endif /* CONFIG_32BIT */
return 0;
}
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index d14a4c3..fe4f02a 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -47,6 +47,8 @@
* runtime initialization.
*/
+struct notifier_block;
+
typedef int (*notifier_fn_t)(struct notifier_block *nb,
unsigned long action, void *data);
@@ -70,12 +72,6 @@ struct raw_notifier_head {
struct notifier_block __rcu *head;
};
-struct srcu_notifier_head {
- struct mutex mutex;
- struct srcu_struct srcu;
- struct notifier_block __rcu *head;
-};
-
#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
spin_lock_init(&(name)->lock); \
(name)->head = NULL; \
@@ -88,11 +84,6 @@ struct srcu_notifier_head {
(name)->head = NULL; \
} while (0)
-/* srcu_notifier_heads must be initialized and cleaned up dynamically */
-extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
-#define srcu_cleanup_notifier_head(name) \
- cleanup_srcu_struct(&(name)->srcu);
-
#define ATOMIC_NOTIFIER_INIT(name) { \
.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
.head = NULL }
@@ -101,7 +92,6 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
.head = NULL }
#define RAW_NOTIFIER_INIT(name) { \
.head = NULL }
-/* srcu_notifier_heads cannot be initialized statically */
#define ATOMIC_NOTIFIER_HEAD(name) \
struct atomic_notifier_head name = \
@@ -121,8 +111,6 @@ extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
struct notifier_block *nb);
extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
struct notifier_block *nb);
-extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
- struct notifier_block *nb);
extern int blocking_notifier_chain_cond_register(
struct blocking_notifier_head *nh,
@@ -134,8 +122,6 @@ extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
struct notifier_block *nb);
extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
struct notifier_block *nb);
-extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
- struct notifier_block *nb);
extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
unsigned long val, void *v);
@@ -149,10 +135,6 @@ extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v);
extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v, int nr_to_call, int *nr_calls);
-extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
- unsigned long val, void *v);
-extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
- unsigned long val, void *v, int nr_to_call, int *nr_calls);
#define NOTIFY_DONE 0x0000 /* Don't care */
#define NOTIFY_OK 0x0001 /* Suits me */
@@ -211,5 +193,30 @@ static inline int notifier_to_errno(int ret)
extern struct blocking_notifier_head reboot_notifier_list;
+#ifdef CONFIG_SRCU
+
+struct srcu_notifier_head {
+ struct mutex mutex;
+ struct srcu_struct srcu;
+ struct notifier_block __rcu *head;
+};
+
+/* srcu_notifier_heads must be initialized and cleaned up dynamically
+ * srcu_notifier_heads cannot be initialized statically
+ */
+extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
+#define srcu_cleanup_notifier_head(name) cleanup_srcu_struct(&(name)->srcu)
+
+extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
+ struct notifier_block *nb);
+extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
+ struct notifier_block *nb);
+extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+ unsigned long val, void *v);
+extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+ unsigned long val, void *v, int nr_to_call, int *nr_calls);
+
+#endif /* CONFIG_SRCU */
+
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 9cfd962..ed9c389 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -26,6 +26,8 @@
*
*/
+#ifdef CONFIG_SRCU
+
#ifndef _LINUX_SRCU_H
#define _LINUX_SRCU_H
@@ -249,4 +251,6 @@ static inline void smp_mb__after_srcu_read_unlock(void)
/* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
}
-#endif
+#endif /* _LINUX_SRCU_H */
+
+#endif /* CONFIG_SRCU */
--
1.9.1
In an allnoconfig we get the following build failure:
arch/powerpc/platforms/built-in.o: In function `.__machine_initcall_powernv_opal_init':
opal.c:(.init.text+0x468): undefined reference to `.log_buf_addr_get'
opal.c:(.init.text+0x474): undefined reference to `.log_buf_len_get'
make: *** [vmlinux] Error 1
This happens because powernv requires printk() support. Enable it in the config
file.
Signed-off-by: Pranith Kumar <[email protected]>
---
arch/powerpc/platforms/powernv/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig
index 45a8ed0..be4f340 100644
--- a/arch/powerpc/platforms/powernv/Kconfig
+++ b/arch/powerpc/platforms/powernv/Kconfig
@@ -18,6 +18,7 @@ config PPC_POWERNV
select CPU_FREQ_GOV_ONDEMAND
select CPU_FREQ_GOV_CONSERVATIVE
select PPC_DOORBELL
+ select PRINTK
default y
config PPC_POWERNV_RTAS
--
1.9.1
On Sat, 2014-12-27 at 12:17 -0500, Pranith Kumar wrote:
> In an allnoconfig we get the following build failure:
An allnoconfig doesn't include CONFIG_PPC_POWERNV? But I think I know what you
mean.
> arch/powerpc/platforms/built-in.o: In function `.__machine_initcall_powernv_opal_init':
> opal.c:(.init.text+0x468): undefined reference to `.log_buf_addr_get'
> opal.c:(.init.text+0x474): undefined reference to `.log_buf_len_get'
> make: *** [vmlinux] Error 1
>
> This happens because powernv requires printk() support. Enable it in the config
> file.
Sort of. It just requires those two routines. Or is there a stronger
dependency?
I think the better fix is for those two routines to be defined for
CONFIG_PRINTK=n, but return NULL and zero respectively.
And the opal code could skip registering the region when they return NULL/zero.
Care to do a couple of patches?
cheers
On Sat, 27 Dec 2014 12:17:43 -0500
Pranith Kumar <[email protected]> wrote:
> @@ -65,10 +65,13 @@
> #include <asm/kexec.h>
> #include <asm/mmu_context.h>
> #include <asm/code-patching.h>
> -#include <asm/kvm_ppc.h>
> #include <asm/hugetlb.h>
> #include <asm/epapr_hcalls.h>
>
> +#if IS_ENABLED(CONFIG_KVM)
> +#include <asm/kvm_ppc.h>
> +#endif
> +
> #ifdef DEBUG
> #define DBG(fmt...) udbg_printf(fmt)
> #else
I always cringe when I see an include protected by an #ifdef.
Is this really necessary? All that is done in asm-offsets.c is
to calculate offsets, the code where the two offsets in question
are used (entry64.S) does have the #ifdef for CONFIG_KVM.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
On Sat, 2014-12-27 at 12:17 -0500, Pranith Kumar wrote:
> Isolate the SRCU functions and data structures within CONFIG_SRCU so that there
> is a compile time failure if srcu is used when not enabled. This was decided to
> be better than waiting until link time for a failure to occur.
Yes, false positives and extra ifdefs are so much better. :-P
Why not just ifdef the functions/macros, and leave the types alone? If
you're worried about direct access to struct members, you could even
ifdef the members away while leaving the struct itself. It is not
normal practice in Linux to need ifdefs around #includes.
> There are places which include kvm headers and utilize kvm data structures
> without checking if KVM is enabled. In two such archs(s390, ppc64), the current
> patch makes the uses of KVM conditional on KVM being enabled. The other option,
> which is to enable KVM unconditionally seemed a bit too much as we could easily
> figure out KVM only parts and enclose them in ifdefs.
Maybe not so easy (mpc85xx_smp_defconfig with NOTIFY stuff turned off so
that SRCU gets deselected):
In file included from /home/scott/fsl/git/linux/upstream/arch/powerpc/include/asm/kvm_ppc.h:30:0,
from /home/scott/fsl/git/linux/upstream/arch/powerpc/kernel/smp.c:39:
/home/scott/fsl/git/linux/upstream/include/linux/kvm_host.h:366:21: error: field 'srcu' has incomplete type
/home/scott/fsl/git/linux/upstream/include/linux/kvm_host.h:367:21: error: field 'irq_srcu' has incomplete type
/home/scott/fsl/git/linux/upstream/scripts/Makefile.build:257: recipe for target 'arch/powerpc/kernel/smp.o' failed
make[2]: *** [arch/powerpc/kernel/smp.o] Error 1
/home/scott/fsl/git/linux/upstream/Makefile:955: recipe for target 'arch/powerpc/kernel' failed
make[1]: *** [arch/powerpc/kernel] Error 2
make[1]: *** Waiting for unfinished jobs....
Are you sure KVM is the only SRCU user so impacted? It's also likely
that new such problems get introduced, because most people are going to
have SRCU enabled and thus not notice the breakage they're adding.
There's also at least one place that needs to be fixed, that currently
expects to get other headers indirectly via srcu.h:
/home/scott/fsl/git/linux/upstream/lib/assoc_array.c: In function 'assoc_array_apply_edit':
/home/scott/fsl/git/linux/upstream/lib/assoc_array.c:1425:2: error: implicit declaration of function 'call_rcu' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
/home/scott/fsl/git/linux/upstream/scripts/Makefile.build:257: recipe for target 'lib/assoc_array.o' failed
-Scott
On Mon, Dec 29, 2014 at 5:03 AM, Martin Schwidefsky
<[email protected]> wrote:
> On Sat, 27 Dec 2014 12:17:43 -0500
> Pranith Kumar <[email protected]> wrote:
>
>> @@ -65,10 +65,13 @@
>> #include <asm/kexec.h>
>> #include <asm/mmu_context.h>
>> #include <asm/code-patching.h>
>> -#include <asm/kvm_ppc.h>
>> #include <asm/hugetlb.h>
>> #include <asm/epapr_hcalls.h>
>>
>> +#if IS_ENABLED(CONFIG_KVM)
>> +#include <asm/kvm_ppc.h>
>> +#endif
>> +
>> #ifdef DEBUG
>> #define DBG(fmt...) udbg_printf(fmt)
>> #else
>
> I always cringe when I see an include protected by an #ifdef.
> Is this really necessary? All that is done in asm-offsets.c is
> to calculate offsets, the code where the two offsets in question
> are used (entry64.S) does have the #ifdef for CONFIG_KVM.
I agree that this is not the ideal way to do this. But, it has been
the way things were already being done. If you see
arch/powerpc/kernel/asm-offsets.c, there are quite some includes which
are within ifdefs.
I've considered other alternatives (though not in-depth) and found
that they will require quite some refactoring. One simple idea is to
move this #ifdef to within kvm_ppc.h. That should make the inclusion
of this file a no-op in all the places where this is being included
without KVM being enabled. But I am not 100% sure of that approach.
Any suggestions are welcome.
--
Pranith
On Mon, Dec 29, 2014 at 6:05 PM, Scott Wood <[email protected]> wrote:
> On Sat, 2014-12-27 at 12:17 -0500, Pranith Kumar wrote:
>> Isolate the SRCU functions and data structures within CONFIG_SRCU so that there
>> is a compile time failure if srcu is used when not enabled. This was decided to
>> be better than waiting until link time for a failure to occur.
>
> Yes, false positives and extra ifdefs are so much better. :-P
>
> Why not just ifdef the functions/macros, and leave the types alone? If
> you're worried about direct access to struct members, you could even
> ifdef the members away while leaving the struct itself. It is not
> normal practice in Linux to need ifdefs around #includes.
Yup, totally agree that this is not ideal. The idea here is to not
even compile the structure for tinification purposes. ifdefs for
headers are ugly, but given the current code structure, I was not able
to figure out any other way around it without major overhaul.
>
>> There are places which include kvm headers and utilize kvm data structures
>> without checking if KVM is enabled. In two such archs(s390, ppc64), the current
>> patch makes the uses of KVM conditional on KVM being enabled. The other option,
>> which is to enable KVM unconditionally seemed a bit too much as we could easily
>> figure out KVM only parts and enclose them in ifdefs.
>
> Maybe not so easy (mpc85xx_smp_defconfig with NOTIFY stuff turned off so
> that SRCU gets deselected):
>
> In file included from /home/scott/fsl/git/linux/upstream/arch/powerpc/include/asm/kvm_ppc.h:30:0,
> from /home/scott/fsl/git/linux/upstream/arch/powerpc/kernel/smp.c:39:
> /home/scott/fsl/git/linux/upstream/include/linux/kvm_host.h:366:21: error: field 'srcu' has incomplete type
> /home/scott/fsl/git/linux/upstream/include/linux/kvm_host.h:367:21: error: field 'irq_srcu' has incomplete type
> /home/scott/fsl/git/linux/upstream/scripts/Makefile.build:257: recipe for target 'arch/powerpc/kernel/smp.o' failed
> make[2]: *** [arch/powerpc/kernel/smp.o] Error 1
> /home/scott/fsl/git/linux/upstream/Makefile:955: recipe for target 'arch/powerpc/kernel' failed
> make[1]: *** [arch/powerpc/kernel] Error 2
> make[1]: *** Waiting for unfinished jobs....
>
> Are you sure KVM is the only SRCU user so impacted? It's also likely
> that new such problems get introduced, because most people are going to
> have SRCU enabled and thus not notice the breakage they're adding.
Well, it is the major one which I encountered until now. There might
be other problems lurking which I will gladly try to fix if and when
they are reported.
>
> There's also at least one place that needs to be fixed, that currently
> expects to get other headers indirectly via srcu.h:
>
> /home/scott/fsl/git/linux/upstream/lib/assoc_array.c: In function 'assoc_array_apply_edit':
> /home/scott/fsl/git/linux/upstream/lib/assoc_array.c:1425:2: error: implicit declaration of function 'call_rcu' [-Werror=implicit-function-declaration]
> cc1: some warnings being treated as errors
> /home/scott/fsl/git/linux/upstream/scripts/Makefile.build:257: recipe for target 'lib/assoc_array.o' failed
I will send a patch fixing this(need to use rcupdate.h here
explicitly). Thanks for reporting these!
>
> -Scott
>
>
--
Pranith
On Mon, Dec 29, 2014 at 4:01 AM, Michael Ellerman <[email protected]> wrote:
> On Sat, 2014-12-27 at 12:17 -0500, Pranith Kumar wrote:
>> In an allnoconfig we get the following build failure:
>
> An allnoconfig doesn't include CONFIG_PPC_POWERNV? But I think I know what you
> mean.
>
>> arch/powerpc/platforms/built-in.o: In function `.__machine_initcall_powernv_opal_init':
>> opal.c:(.init.text+0x468): undefined reference to `.log_buf_addr_get'
>> opal.c:(.init.text+0x474): undefined reference to `.log_buf_len_get'
>> make: *** [vmlinux] Error 1
>>
>> This happens because powernv requires printk() support. Enable it in the config
>> file.
>
> Sort of. It just requires those two routines. Or is there a stronger
> dependency?
>
> I think the better fix is for those two routines to be defined for
> CONFIG_PRINTK=n, but return NULL and zero respectively.
>
> And the opal code could skip registering the region when they return NULL/zero.
>
> Care to do a couple of patches?
>
Sure, I will give it a try. Thanks for the review!
--
Pranith
On Mon, 2014-12-29 at 23:32 -0500, Pranith Kumar wrote:
> On Mon, Dec 29, 2014 at 5:03 AM, Martin Schwidefsky
> <[email protected]> wrote:
> > On Sat, 27 Dec 2014 12:17:43 -0500
> > Pranith Kumar <[email protected]> wrote:
> >
> >> @@ -65,10 +65,13 @@
> >> #include <asm/kexec.h>
> >> #include <asm/mmu_context.h>
> >> #include <asm/code-patching.h>
> >> -#include <asm/kvm_ppc.h>
> >> #include <asm/hugetlb.h>
> >> #include <asm/epapr_hcalls.h>
> >>
> >> +#if IS_ENABLED(CONFIG_KVM)
> >> +#include <asm/kvm_ppc.h>
> >> +#endif
> >> +
> >> #ifdef DEBUG
> >> #define DBG(fmt...) udbg_printf(fmt)
> >> #else
> >
> > I always cringe when I see an include protected by an #ifdef.
> > Is this really necessary? All that is done in asm-offsets.c is
> > to calculate offsets, the code where the two offsets in question
> > are used (entry64.S) does have the #ifdef for CONFIG_KVM.
>
> I agree that this is not the ideal way to do this. But, it has been
> the way things were already being done. If you see
> arch/powerpc/kernel/asm-offsets.c, there are quite some includes which
> are within ifdefs.
asm-offsets.c is unusual in that respect, and I think most of those
ifdefs could go away without breaking anything (head_booke.h is not a
normal header file, and kvm_book3s.h should just be removed as it will
be pulled in by kvm_ppc.h if applicable).
> I've considered other alternatives (though not in-depth) and found
> that they will require quite some refactoring. One simple idea is to
> move this #ifdef to within kvm_ppc.h. That should make the inclusion
> of this file a no-op in all the places where this is being included
> without KVM being enabled. But I am not 100% sure of that approach.
>
> Any suggestions are welcome.
As I suggested elsewhere in the thread, why not be more fine-grained in
what you ifdef in the srcu header? How will that require excessive
refactoring?
Or, just stick with the linker error.
I also wonder if this is worthwhile just to save around 2000 bytes.
What other core synchronization mechanisms are optional? What
real-world configs will actually have this disabled?
-Scott