[PATCH 0/1] x86_64: x86_64_cleanup_pda() should use nr_cpu_ids instead of NR_CPUS

[PATCH 0/1] x86_64: x86_64_cleanup_pda() should use nr_cpu_ids instead of NR_CPUS

[Mike Travis]

Hi Andrew - would you add this to your -mm patchset?  It fixes a
possible panic.

(I based it on 2.6.25-rc2 + 2.6.25-rc2-mm1 + my patches from broken-out-0223
as I could not get 2.6.25-rc2 + all of broken-out-0223 to apply.)

Thanks, Mike

..from Eric Dumazet:
> You might want to apply this patch.
> 
> I also wonder if _cpu_pda should be set only at the very end of 
> x86_64_cleanup_pda(), after array initialization, or maybe other
> cpus are not yet running ? (Sorry I cannot boot test this patch at this
> moment)
> 
> [PATCH] x86_64: x86_64_cleanup_pda() should use nr_cpu_ids instead of NR_CPUS
> 
> We allocate an array of nr_cpu_ids pointers, so we should respect its bonds.
> 
> Delay change of _cpu_pda after array initialization.
> 
> Also take into account that alloc_bootmem_low() :
> - calls panic() if not enough memory
> - already clears allocated memory

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Mike Travis <travis@sgi.com>
---

Built and tested: (x86_64) defconfig, nonum, nosmp (*).
Built: (x86_64) all{yes,mod}config,
       (i386) defconfig, all{yes,mod}config, nonum, nosmp.

* - I add to disable ACPI to build the non-smp version of x86_64.

---

-- 

[PATCH 1/1] x86_64: x86_64_cleanup_pda() should use nr_cpu_ids instead of NR_CPUS

[Mike Travis]

[-- Attachment #1: fold-pda-fix --]
[-- Type: text/plain, Size: 1225 bytes --]

We allocate an array of nr_cpu_ids pointers, so we should respect its bonds.

Delay change of _cpu_pda after array initialization.

Also take into account that alloc_bootmem_low() :
- calls panic() if not enough memory
- already clears allocated memory

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Mike Travis <travis@sgi.com>

---
 arch/x86/kernel/head64.c |   16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -151,18 +151,16 @@ void __init x86_64_start_kernel(char * r
 void __init x86_64_cleanup_pda(void)
 {
 	int i;
+	struct x8664_pda **new_cpu_pda;
 
-	_cpu_pda = alloc_bootmem_low(nr_cpu_ids * sizeof(void *));
+	new_cpu_pda = alloc_bootmem_low(nr_cpu_ids * sizeof(void *));
 
-	if (!_cpu_pda)
-		panic("Cannot allocate cpu pda table\n");
 
+	for (i = 0; i < nr_cpu_ids; i++)
+		if (_cpu_pda_init[i] != &boot_cpu_pda[i])
+			new_cpu_pda[i] = _cpu_pda_init[i];
+	mb();
+	_cpu_pda = new_cpu_pda;
 	/* cpu_pda() now points to allocated cpu_pda_table */
-
-	for (i = 0; i < NR_CPUS; i++)
-		if (_cpu_pda_init[i] == &boot_cpu_pda[i])
-			cpu_pda(i) = NULL;
-		else
-			cpu_pda(i) = _cpu_pda_init[i];
 }
 #endif

--