2013-09-24 08:18:44

by Christophe Leroy

Subject: [PATCH v4] powerpc 8xx: Fixing issue with CONFIG_PIN_TLB

Activating CONFIG_PIN_TLB is supposed to pin the IMMR and the first three
8Mbytes pages. But the setting of MD_CTR to a pinnable entry was missing before
the pinning of the third 8Mb page. As the index is decremented module 28
(MD_RSV4D is set) after every DTLB update, the third 8Mbytes page was
not pinned.

Signed-off-by: Christophe Leroy <[email protected]>

diff -ur linux-3.11.org/arch/powerpc/kernel/head_8xx.S linux-3.11/arch/powerpc/kernel/head_8xx.S
--- linux-3.11.org/arch/powerpc/kernel/head_8xx.S 2013-09-02 22:46:10.000000000 +0200
+++ linux-3.11/arch/powerpc/kernel/head_8xx.S 2013-09-09 11:28:54.000000000 +0200
@@ -862,6 +862,9 @@
addis r11, r11, 0x0080 /* Add 8M */
mtspr SPRN_MD_RPN, r11

+ addi r10, r10, 0x0100
+ mtspr SPRN_MD_CTR, r10
+
addis r8, r8, 0x0080 /* Add 8M */
mtspr SPRN_MD_EPN, r8
mtspr SPRN_MD_TWC, r9

2013-09-27 21:44:00

by Scott Wood

Subject: Re: [PATCH v4] powerpc 8xx: Fixing issue with CONFIG_PIN_TLB

On Tue, 2013-09-24 at 10:18 +0200, Christophe Leroy wrote:
> Activating CONFIG_PIN_TLB is supposed to pin the IMMR and the first three
> 8Mbytes pages. But the setting of MD_CTR to a pinnable entry was missing before
> the pinning of the third 8Mb page. As the index is decremented module 28
> (MD_RSV4D is set) after every DTLB update, the third 8Mbytes page was
> not pinned.

The examples you showed weren't quite modulo 28, more like "if (x >= 28)
x -= 4". I'll fix up the changelog on applying, to read something like
"As the index is decremented to a value within the first 28 entries
(MD_RSV4D is set)...".

-Scott