[PATCH] powerpc/40x: Map 32Mbytes of memory at startup

[PATCH] powerpc/40x: Map 32Mbytes of memory at startup

[Christophe Leroy]

As reported by Carlo, 16Mbytes is not enough with modern kernels
that tend to be a bit big, so map another 16M page at boot.

Cc: cp <carlojpisani@gmail.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/head_40x.S | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 7d72ee5ab387..5fce4680d2d3 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -650,7 +650,7 @@ start_here:
 	b	.		/* prevent prefetch past rfi */
 
 /* Set up the initial MMU state so we can do the first level of
- * kernel initialization.  This maps the first 16 MBytes of memory 1:1
+ * kernel initialization.  This maps the first 32 MBytes of memory 1:1
  * virtual to physical and more importantly sets the cache mode.
  */
 initial_mmu:
@@ -687,6 +687,12 @@ initial_mmu:
 	tlbwe	r4,r0,TLB_DATA		/* Load the data portion of the entry */
 	tlbwe	r3,r0,TLB_TAG		/* Load the tag portion of the entry */
 
+	li	r0,62			/* TLB slot 62 */
+	addis	r4,r4,SZ_16M
+	addis	r3,r3,SZ_16M
+	tlbwe	r4,r0,TLB_DATA		/* Load the data portion of the entry */
+	tlbwe	r3,r0,TLB_TAG		/* Load the tag portion of the entry */
+
 	isync
 
 	/* Establish the exception vector base
-- 
2.31.1

Re: [PATCH] powerpc/40x: Map 32Mbytes of memory at startup

[cp]

hi,
this is my second patch-test report.

Today I have successfully tested Christophe Leroy's patch.

Attached a cleaned patch. With the previous one the kernel booted, but
there was a line missing.

I have also tested two different kernels with success

both kernel sizes were ~9.4MB
the Entry Point was always 0x00901b00

used toolchain:
- powerpc-unknown-linux-gnu-binutiles-v2.34
- powerpc-unknown-linux-gnu-gcc-v9.3.0

host:
- macmini-intel, Gentoo cross-compiler, 32bit userland

target:
- AMCC PPC405GP

wrapper:
- cuboot

Applied to
- kernel-v5.2.1-vanilla
- kernel-v5.7.19-vanilla

Attached I report here is the difference between the original file and mine.

Thanks guys!
Carlo

-----------------------
map 32MB of ram rather than 16MB
--- arch/powerpc/kernel/head_40x.S.original     2021-09-28
00:07:27.768000000 -0000
+++ arch/powerpc/kernel/head_40x.S      2021-09-28 00:07:27.760000000 -0000
@@ -25,6 +25,7 @@
  *      Kernel execution entry point code.
  */

+
 #include <linux/init.h>
 #include <asm/processor.h>
 #include <asm/page.h>
@@ -842,17 +843,33 @@
        mtspr   SPRN_PID,r0
        sync

-       /* Configure and load one entry into TLB slots 63 */
-       clrrwi  r4,r4,10                /* Mask off the real page number */
-       ori     r4,r4,(TLB_WR | TLB_EX) /* Set the write and execute bits */
-
-       clrrwi  r3,r3,10                /* Mask off the effective page number */
-       ori     r3,r3,(TLB_VALID | TLB_PAGESZ(PAGESZ_16M))
-
-        li      r0,63                    /* TLB slot 63 */
-
-       tlbwe   r4,r0,TLB_DATA          /* Load the data portion of the entry */
-       tlbwe   r3,r0,TLB_TAG           /* Load the tag portion of the entry */
+        /*
+         * Configure and load two entries into TLB slots 62 and 63.
+         *     TLB 62 is used for first 16M page
+         *     TLB 63 is for the second 16M page
+         * In case we are pinning TLBs, these are reserved in by
+         * the other TLB functions.
+         * If not reserved, then it doesn't matter where they are loaded.
+         */
+        clrrwi r4,r4,10                 /* Mask off the real page number */
+        ori    r4,r4,(TLB_WR | TLB_EX)  /* Set the write and execute bits */
+
+        clrrwi r3,r3,10                 /* Mask off the effective
page number */
+        ori    r3,r3,(TLB_VALID | TLB_PAGESZ(PAGESZ_16M))
+
+        li     r0,62                    /* TLB slot 62 */
+
+        tlbwe  r4,r0,TLB_DATA           /* Load the data portion of
the entry */
+        tlbwe  r3,r0,TLB_TAG            /* Load the tag portion of the entry */
+
+        addis  r4, r4, 0x0100           /* Map next 16 Mentries */
+        addis  r3, r3, 0x0100
+
+        li      r0,63                   /* TLB slot 63 */
+
+        /* Load up the kernel context */
+        tlbwe   r4,r0,TLB_DATA          /* Load the data portion of
the entry */
+        tlbwe   r3,r0,TLB_TAG           /* Load the tag portion of the entry */

        isync




On Mon, 27 Sept 2021 at 12:35, Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> As reported by Carlo, 16Mbytes is not enough with modern kernels
> that tend to be a bit big, so map another 16M page at boot.

Re: [PATCH] powerpc/40x: Map 32Mbytes of memory at startup

[Michael Ellerman]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> As reported by Carlo, 16Mbytes is not enough with modern kernels
> that tend to be a bit big, so map another 16M page at boot.

I guess we're not expecting systems with less than 32MB, so making it
unconditional is OK?

cheers

> diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
> index 7d72ee5ab387..5fce4680d2d3 100644
> --- a/arch/powerpc/kernel/head_40x.S
> +++ b/arch/powerpc/kernel/head_40x.S
> @@ -650,7 +650,7 @@ start_here:
>  	b	.		/* prevent prefetch past rfi */
>  
>  /* Set up the initial MMU state so we can do the first level of
> - * kernel initialization.  This maps the first 16 MBytes of memory 1:1
> + * kernel initialization.  This maps the first 32 MBytes of memory 1:1
>   * virtual to physical and more importantly sets the cache mode.
>   */
>  initial_mmu:
> @@ -687,6 +687,12 @@ initial_mmu:
>  	tlbwe	r4,r0,TLB_DATA		/* Load the data portion of the entry */
>  	tlbwe	r3,r0,TLB_TAG		/* Load the tag portion of the entry */
>  
> +	li	r0,62			/* TLB slot 62 */
> +	addis	r4,r4,SZ_16M
> +	addis	r3,r3,SZ_16M
> +	tlbwe	r4,r0,TLB_DATA		/* Load the data portion of the entry */
> +	tlbwe	r3,r0,TLB_TAG		/* Load the tag portion of the entry */
> +
>  	isync
>  
>  	/* Establish the exception vector base
> -- 
> 2.31.1

Re: [PATCH] powerpc/40x: Map 32Mbytes of memory at startup

[cp]

> I guess we're not expecting systems with less than 32MB, so making it
> unconditional is OK?

hi
it's not 32MB of total physical ram, but rather using 32MB of the
total physical ram to correctly boot a kernel bigger than 8MB.

The problem is complex:
- u-boot loads things at 0x0200.0000 (in my case)
- then cuboot copies the kernel to 0x0090.0000, and appends the flat
device tree to the end of kernel
- then cuboot copies again the kernel to 0x0000.0000, and invokes head.S

at this point head.S needs to initialize the virtual memory, and needs
to have 32MB mapped in order to correctly gets the flat device tree

if the kernel is smaller than 8MB, then cuboot copies it to
0x0080.0000, and head.S only need to have 16MB mapped in order to gets
the flat device tree

Cheers

ppc32 doesn't boot when linkaddr=0x00900000

[cp]

hi
I am new to this list. Hope this is the right place to ask.

I am working with a PPC405GP board, and as far as I understand, the
support for ppc40x platforms like Acadia and Walnut were dropped with
kernel 5.8.0, so this seems like a pretty straightforward question,
but extensive experiments from kernel 4.11 to kernel 5.7.19 haven't
shown a really clear, up-to-date answer.

In k4.11 .. k5.7.19, when the kernel size is bigger than 8 MB, the
final kernel doesn't boot but rather arch/powerpc/boot/main.c dies
before the first message from the kernel shows up.

Why?

Digging deeper I see the relation between the kernel size and link_addr

        # Round the size to next higher MB limit
        round_size=$(((strip_size + 0xfffff) & 0xfff00000))

        round_size=0x$(printf "%x" $round_size)
        link_addr=$(printf "%d" $link_address)

and this is where link_addr is involved

        text_start="-Ttext $link_address"

My kernels are compiled for cuboot, and the code that invokes "kentry"
is entirely located in arch/powerpc/boot/main.c

I instrumned that module, and this is what I see on the condole

The following is the same kernel, compiled with the same .config, but
with two link_addr values

A) with link_addr=0x0080.0000
image loaded from 0x00800000
SP=0x03eb1b80
kernel_size = 7411084 bytes
copying 256 bytes from kernel-image at 0x0080f000 to elfheader
elf_info.loadsize = 0x00700e68
elf_info.memsize  = 0x0074234c
allocating 7611212 bytes for the new kernel
copying ...
from = 0x0081f000
to = 0x00000000
size = 7343720
flush_cache, 32Mbyte flushed
cmdline: uboot bootargs overridden
cmdline=[console=ttyS0,115200 root=/dev/sda2 rootfstype=ext2 rw
init=/sbin/init ]
Finalizing device tree... flat tree at 0xf23b80
ft_addr=0xf23b80
my tp1: success
kernel booting ....
(it boots)

B) with link_addr=0x0080.0000
image loaded from 0x00900000
SP=0x03eb1b80
kernel_size = 7411084
copying 256 bytes from kernel-image at 0x0090f000 to elfheader
elf_info.loadsize = 0x00700e68
elf_info.memsize  = 0x0074234c
allocating 7611212 bytes for the new kernel
copying ...
from = 0x0091f000
to = 0x00000000
size = 7343720
flush_cache, 32Mbyte flushed
cmdline: uboot bootargs overridden
cmdline=[console=ttyS0,115200 root=/dev/sda2 rootfstype=ext2 rw
init=/sbin/init ]
Finalizing device tree... flat tree at 0x1023b80
ft_addr=0x1023b80
my tp2: success
my tp3: success
invalidate_cache 0x00000000+0x02000000
my tp4: (point of no return)
calling kentry()...
kernel booting ....
(it dies at this point, but without a debugger it's like watching
something fall into a black hole)

Any ideas?
I am lost ...

Carlo

Re: [PATCH] powerpc/40x: Map 32Mbytes of memory at startup

[cp]

hi,
this is my first patch-test report.

Today I have successfully tested Christophe Leroy's patch.
I had to manually edit lines, but it worked with a kernel sized 9.1MByte :D

used toolchain:
- powerpc-unknown-linux-gnu-binutiles-v2.34
- powerpc-unknown-linux-gnu-gcc-v9.3.0

host:
- macmini-intel, Gentoo cross-compiler

target:
- AMCC PPC405GP

wrapper:
- cuboot

Applied to kernel-v5.2.1-vanilla

Attached I report here is the difference between the original file and mine.

Thanks guys!
Carlo

----------------
Map 32Mbytes rather than 16MB of memory at startup
--- arch/powerpc/kernel/head_40x.S.original     2021-09-27
16:32:04.536000000 -0000
+++ arch/powerpc/kernel/head_40x.S      2021-09-27 16:32:04.532000000 -0000
@@ -38,6 +38,8 @@
 #include <asm/export.h>
 #include <asm/asm-405.h>

+#include <linux/sizes.h> /* hack, include/linux/sizes.h defines "SZ_16M" */
+
 #include "head_32.h"

 /* As with the other PowerPC ports, it is expected that when code
@@ -839,18 +841,25 @@
        mtspr   SPRN_PID,r0
        sync

-       /* Configure and load one entry into TLB slots 63 */
+       /* Configure and load one entry into TLB slots 62/63 */ /* hacked */
        clrrwi  r4,r4,10                /* Mask off the real page number */
        ori     r4,r4,(TLB_WR | TLB_EX) /* Set the write and execute bits */

        clrrwi  r3,r3,10                /* Mask off the effective page number */
        ori     r3,r3,(TLB_VALID | TLB_PAGESZ(PAGESZ_16M))

-        li      r0,63                    /* TLB slot 63 */
-
+//-- hack begin
-----------------------------------------------------------------------------
+// TLB 63 is used for first 16M page
+// TLB 62 is for the second 16M page
+//        li      r0,63                    /* TLB slot 63 */ /* original */
+        li      r0,62                    /* TLB slot 62 */ /* hacked */
+// ------------------------------------------------------------------------------------------
        tlbwe   r4,r0,TLB_DATA          /* Load the data portion of the entry */
        tlbwe   r3,r0,TLB_TAG           /* Load the tag portion of the entry */
-
+// ------------------------------------------------------------------------------------------
+        addis   r4,r4,SZ_16M@h           /* added, hacked */
+        addis   r3,r3,SZ_16M@h           /* added, hacked */
+//-- hack end -----------------------------------------------------------------------------


        isync

        /* Establish the exception vector base