[PATCH] x86: Remove 6 bank limitation in 64 bit MCE reporting code

[PATCH] x86: Remove 6 bank limitation in 64 bit MCE reporting code

[Venki Pallipadi]

Eliminate the 6 bank restriction in 64 bit mce reporting code. This restriction
is artificial (due to static creation of sysfs files) and 32 bit code
does not have any such restriction.

This change helps in reporting the details of machine checks on a machine check
exception with errors in bank 6 and above on CPUs that support those banks.
Without the patch, machine check errors in those banks are not reported.

We still have 128 (MCE_EXTENDED_BANK) bank restriction instead of max 256
supported in hardware. That is not changed in the patch below as it will have
some user level mcelog utility dependency, with bank 128 being used for
thermal reporting currently.

The patch below does not create sysfs control (bankNctl) for banks higher
than 6 as well. That needs some pre-cleanup in /sysfs mce layout, removal of
per cpu /sysfs entries for bankctl as they are really global system level
control today. That change will follow. This basic change is critical to
report the detailed errors on banks higher than 6.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

---
 arch/x86/kernel/cpu/mcheck/mce_64.c |   20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

Index: linux-2.6/arch/x86/kernel/cpu/mcheck/mce_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/mcheck/mce_64.c	2008-05-08 13:27:53.000000000 -0700
+++ linux-2.6/arch/x86/kernel/cpu/mcheck/mce_64.c	2008-05-08 14:07:10.000000000 -0700
@@ -31,7 +31,7 @@
 #include <asm/idle.h>
 
 #define MISC_MCELOG_MINOR 227
-#define NR_BANKS 6
+#define NR_SYSFS_BANKS 6
 
 atomic_t mce_entry;
 
@@ -46,7 +46,7 @@ static int mce_dont_init;
  */
 static int tolerant = 1;
 static int banks;
-static unsigned long bank[NR_BANKS] = { [0 ... NR_BANKS-1] = ~0UL };
+static unsigned long bank[NR_SYSFS_BANKS] = { [0 ... NR_SYSFS_BANKS-1] = ~0UL };
 static unsigned long notify_user;
 static int rip_msr;
 static int mce_bootlog = -1;
@@ -209,7 +209,7 @@ void do_machine_check(struct pt_regs * r
 	barrier();
 
 	for (i = 0; i < banks; i++) {
-		if (!bank[i])
+		if (i < NR_SYSFS_BANKS && !bank[i])
 			continue;
 
 		m.misc = 0;
@@ -444,9 +444,10 @@ static void mce_init(void *dummy)
 
 	rdmsrl(MSR_IA32_MCG_CAP, cap);
 	banks = cap & 0xff;
-	if (banks > NR_BANKS) {
-		printk(KERN_INFO "MCE: warning: using only %d banks\n", banks);
-		banks = NR_BANKS;
+	if (banks > MCE_EXTENDED_BANK) {
+		printk(KERN_INFO "MCE: warning: using only %d banks\n",
+		       MCE_EXTENDED_BANK);
+		banks = MCE_EXTENDED_BANK;
 	}
 	/* Use accurate RIP reporting if available. */
 	if ((cap & (1<<9)) && ((cap >> 16) & 0xff) >= 9)
@@ -462,7 +463,7 @@ static void mce_init(void *dummy)
 		wrmsr(MSR_IA32_MCG_CTL, 0xffffffff, 0xffffffff);
 
 	for (i = 0; i < banks; i++) {
-		wrmsrl(MSR_IA32_MC0_CTL+4*i, bank[i]);
+		wrmsrl(MSR_IA32_MC0_CTL+4*i, ~0UL);
 		wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0);
 	}
 }
@@ -766,7 +767,10 @@ DEFINE_PER_CPU(struct sys_device, device
 	}								\
 	static SYSDEV_ATTR(name, 0644, show_ ## name, set_ ## name);
 
-/* TBD should generate these dynamically based on number of available banks */
+/*
+ * TBD should generate these dynamically based on number of available banks.
+ * Have only 6 contol banks in /sysfs until then.
+ */
 ACCESSOR(bank0ctl,bank[0],mce_restart())
 ACCESSOR(bank1ctl,bank[1],mce_restart())
 ACCESSOR(bank2ctl,bank[2],mce_restart())

Re: [PATCH] x86: Remove 6 bank limitation in 64 bit MCE reporting code

[H. Peter Anvin]

Venki Pallipadi wrote:
> Eliminate the 6 bank restriction in 64 bit mce reporting code. This restriction
> is artificial (due to static creation of sysfs files) and 32 bit code
> does not have any such restriction.
> 
> This change helps in reporting the details of machine checks on a machine check
> exception with errors in bank 6 and above on CPUs that support those banks.
> Without the patch, machine check errors in those banks are not reported.
> 
> We still have 128 (MCE_EXTENDED_BANK) bank restriction instead of max 256
> supported in hardware. That is not changed in the patch below as it will have
> some user level mcelog utility dependency, with bank 128 being used for
> thermal reporting currently.
> 
> The patch below does not create sysfs control (bankNctl) for banks higher
> than 6 as well. That needs some pre-cleanup in /sysfs mce layout, removal of
> per cpu /sysfs entries for bankctl as they are really global system level
> control today. That change will follow. This basic change is critical to
> report the detailed errors on banks higher than 6.
> 
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

Any chance you could add unifying the 32 and 64-bit code to your list, 
since you're already working on eliminating differences there?

	-hpa

Re: [PATCH] x86: Remove 6 bank limitation in 64 bit MCE reporting code

[Venki Pallipadi]

On Thu, May 08, 2008 at 02:27:58PM -0700, H. Peter Anvin wrote:
> Venki Pallipadi wrote:
> >Eliminate the 6 bank restriction in 64 bit mce reporting code. This 
> >restriction
> >is artificial (due to static creation of sysfs files) and 32 bit code
> >does not have any such restriction.
> >
> >This change helps in reporting the details of machine checks on a machine 
> >check
> >exception with errors in bank 6 and above on CPUs that support those banks.
> >Without the patch, machine check errors in those banks are not reported.
> >
> >We still have 128 (MCE_EXTENDED_BANK) bank restriction instead of max 256
> >supported in hardware. That is not changed in the patch below as it will 
> >have
> >some user level mcelog utility dependency, with bank 128 being used for
> >thermal reporting currently.
> >
> >The patch below does not create sysfs control (bankNctl) for banks higher
> >than 6 as well. That needs some pre-cleanup in /sysfs mce layout, removal 
> >of
> >per cpu /sysfs entries for bankctl as they are really global system level
> >control today. That change will follow. This basic change is critical to
> >report the detailed errors on banks higher than 6.
> >
> >Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> 
> Any chance you could add unifying the 32 and 64-bit code to your list, 
> since you're already working on eliminating differences there?
> 

It was tried earlier
http://www.ussg.iu.edu/hypermail/linux/kernel/0505.2/0982.html
but never made it.

Yes. Will add that to the todo list.

Thanks,
Venki

Re: [PATCH] x86: Remove 6 bank limitation in 64 bit MCE reporting code

[Ingo Molnar]

* Venki Pallipadi <venkatesh.pallipadi@intel.com> wrote:

> It was tried earlier
> http://www.ussg.iu.edu/hypermail/linux/kernel/0505.2/0982.html
> but never made it.

yeah - it had some test failures iirc.

> Yes. Will add that to the todo list.

great.

queued up this patch of yours as well.

	Ingo