Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

Le 10/02/2020 à 13:55, Larry Finger a écrit :
> On 2/9/20 12:19 PM, Christophe Leroy wrote:
>> Do you have CONFIG_TRACE_IRQFLAGS in your config ?
>> If so, can you try the patch below ?
>>
>> https://patchwork.ozlabs.org/patch/1235081/
>>
>> Otherwise, can you send me your .config and tell me exactly where it 
>> stops during the boot.
> 
> Christophe,
> 
> That patch did not work. My .config is attached.
> 
> It does boot if CONFIG_VMAP_STACK is not set.
> 
> The console display ends with the "DMA ranges" output. A screen shot is 
> also appended.
> 
> Larry
> 

Hi,

I tried your config under QEMU, it works.

In fact your console display is looping on itself, it ends at "printk: 
bootconsole [udbg0] disabled".

Looks like you get stuck at the time of switching to graphic mode. Need 
to understand why.

Christophe

Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Larry Finger]

On 2/11/20 12:55 AM, Christophe Leroy wrote:
> 
> 
> Le 10/02/2020 à 13:55, Larry Finger a écrit :
>> On 2/9/20 12:19 PM, Christophe Leroy wrote:
>>> Do you have CONFIG_TRACE_IRQFLAGS in your config ?
>>> If so, can you try the patch below ?
>>>
>>> https://patchwork.ozlabs.org/patch/1235081/
>>>
>>> Otherwise, can you send me your .config and tell me exactly where it stops 
>>> during the boot.
>>
>> Christophe,
>>
>> That patch did not work. My .config is attached.
>>
>> It does boot if CONFIG_VMAP_STACK is not set.
>>
>> The console display ends with the "DMA ranges" output. A screen shot is also 
>> appended.
>>
>> Larry
>>
> 
> Hi,
> 
> I tried your config under QEMU, it works.
> 
> In fact your console display is looping on itself, it ends at "printk: 
> bootconsole [udbg0] disabled".
> 
> Looks like you get stuck at the time of switching to graphic mode. Need to 
> understand why.

I'm not surprised that a real G4 differs from QEMU. For one thing, the real 
hardware uses i2c to connect to the graphics hardware.

I realized that the screen was not scrolling and output was missing. To see what 
was missed, I added a call to btext_clearscreen(). As you noted, it ends at the 
bootconsole disabled statement.

As I could not find any console output after that point, I then turned off the 
bootconsole disable. I realize this action may cause a different problem, but in 
this configuration, the computer hit a BUG Unable to handle kernel data access 
at 0x007a84fc. The faulting instruction address was 0x00013674. Those addresses 
look like physical, not virtual, addresses.

I then added pr_info statements to bracket the failure. In file 
drivers/video/fbdev/core/fb_ddc.c, the code reaches line 66, which is
	algo_data->setsda(algo_data->data, 1);
Both pointers seem OK with algo_data = 0xeedfb4bc, and algo_data->data = 
0xeedb25c. The code faults before returning. I then annotated that callback 
routine radeon_gpio_setsda(), and found that execution is OK to the end of the 
routine, but the fault happens on the return from this routine as though the 
stack were corrupted.

I will be busy for about 8 hours, but if you can think of any debugging I can do 
on this routine, please let me know.

Thanks,

Larry

Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

Le 11/02/2020 à 17:06, Larry Finger a écrit :
> On 2/11/20 12:55 AM, Christophe Leroy wrote:
>>
>>
>> Le 10/02/2020 à 13:55, Larry Finger a écrit :
>>> On 2/9/20 12:19 PM, Christophe Leroy wrote:
>>>> Do you have CONFIG_TRACE_IRQFLAGS in your config ?
>>>> If so, can you try the patch below ?
>>>>
>>>> https://patchwork.ozlabs.org/patch/1235081/
>>>>
>>>> Otherwise, can you send me your .config and tell me exactly where it 
>>>> stops during the boot.
>>>
>>> Christophe,
>>>
>>> That patch did not work. My .config is attached.
>>>
>>> It does boot if CONFIG_VMAP_STACK is not set.
>>>
>>> The console display ends with the "DMA ranges" output. A screen shot 
>>> is also appended.
>>>
>>> Larry
>>>
>>
>> Hi,
>>
>> I tried your config under QEMU, it works.
>>
>> In fact your console display is looping on itself, it ends at "printk: 
>> bootconsole [udbg0] disabled".
>>
>> Looks like you get stuck at the time of switching to graphic mode. 
>> Need to understand why.
> 
> I'm not surprised that a real G4 differs from QEMU. For one thing, the 
> real hardware uses i2c to connect to the graphics hardware.
> 
> I realized that the screen was not scrolling and output was missing. To 
> see what was missed, I added a call to btext_clearscreen(). As you 
> noted, it ends at the bootconsole disabled statement.
> 
> As I could not find any console output after that point, I then turned 
> off the bootconsole disable. I realize this action may cause a different 
> problem, but in this configuration, the computer hit a BUG Unable to 
> handle kernel data access at 0x007a84fc. The faulting instruction 
> address was 0x00013674. Those addresses look like physical, not virtual, 
> addresses.
> 

Can you send me a picture of that BUG Unable to handle kernel data 
access with all the registers values etc..., together with the matching 
vmlinux ?

First thing is to identify where we are when that happens. That mean see 
what is at 0xc0013674. Can be done with 'ppc-linux-objdump -d vmlinux' 
(Or whatever your PPC objdump is named) and get the function code.

Then we need to understand how we reach that function and why it tries 
to access a physical address.


Another thing I'm thinking about, not necessarily related to that 
problem: Some buggy drivers do DMA from stack. This doesn't work anymore 
with CONFIG_VMAP_STACK. Most of them can be detected with 
CONFIG_DEBUG_VIRTUAL so you should activate it.

Christophe

Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

On 02/12/2020 11:02 PM, Larry Finger wrote:
> On 2/11/20 1:23 PM, Christophe Leroy wrote:
>>
>> Can you send me a picture of that BUG Unable to handle kernel data 
>> access with all the registers values etc..., together with the 
>> matching vmlinux ?
> 
> The vmlinux file was too big for your mailbox. You can download it from 
> http://www.lwfinger.com/download/vmlinux.gz
> 

Hi,

Is that the vmlinux that corresponds to:

	BUG Unable to handle kernel data access at 0x007a84fc.
	The faulting instruction address was 0x00013674

Nevertheless, do you have a picture of the said BUG/Oops to see all 
registers ?

Because here, the address 0x13674 is not a data access:

c00135ec <ppc6xx_idle>:
c00135ec:	3c 60 00 00 	lis     r3,0
c00135f0:	3c 60 00 80 	lis     r3,128
c00135f4:	3c 80 c0 83 	lis     r4,-16253
c00135f8:	80 84 f2 80 	lwz     r4,-3456(r4)
c00135fc:	80 84 00 0c 	lwz     r4,12(r4)
c0013600:	70 80 00 08 	andi.   r0,r4,8
c0013604:	41 82 00 18 	beq     c001361c <ppc6xx_idle+0x30>
c0013608:	3c 80 c0 84 	lis     r4,-16252
c001360c:	80 84 30 34 	lwz     r4,12340(r4)
c0013610:	2c 04 00 00 	cmpwi   r4,0
c0013614:	41 82 00 08 	beq     c001361c <ppc6xx_idle+0x30>
c0013618:	3c 60 00 40 	lis     r3,64
c001361c:	2c 03 00 00 	cmpwi   r3,0
c0013620:	4d 82 00 20 	beqlr
c0013624:	74 60 00 40 	andis.  r0,r3,64
c0013628:	41 82 00 30 	beq     c0013658 <ppc6xx_idle+0x6c>
c001362c:	7c 96 fa a6 	mfspr   r4,1014
c0013630:	54 84 00 3a 	rlwinm  r4,r4,0,0,29
c0013634:	7c 00 04 ac 	hwsync
c0013638:	7c 96 fb a6 	mtspr   1014,r4
c001363c:	7c 00 04 ac 	hwsync
c0013640:	4c 00 01 2c 	isync
c0013644:	3c 80 c0 00 	lis     r4,-16384
c0013648:	7c 00 20 ac 	dcbf    0,r4
c001364c:	7c 00 20 ac 	dcbf    0,r4
c0013650:	7c 00 20 ac 	dcbf    0,r4
c0013654:	7c 00 20 ac 	dcbf    0,r4
c0013658:	3c 80 c0 7c 	lis     r4,-16260
c001365c:	80 84 92 64 	lwz     r4,-28060(r4)
c0013660:	2c 04 00 00 	cmpwi   r4,0
c0013664:	41 82 00 10 	beq     c0013674 <ppc6xx_idle+0x88>
c0013668:	7c 91 fa a6 	mfspr   r4,1009
c001366c:	64 84 00 01 	oris    r4,r4,1
c0013670:	7c 91 fb a6 	mtspr   1009,r4
 >> c0013674:	7c 90 fa a6 	mfspr   r4,1008
c0013678:	3c a0 00 60 	lis     r5,96
c001367c:	64 a5 00 80 	oris    r5,r5,128
c0013680:	7c 84 28 78 	andc    r4,r4,r5
c0013684:	7c 84 1b 78 	or      r4,r4,r3
c0013688:	64 84 00 10 	oris    r4,r4,16
c001368c:	7c 90 fb a6 	mtspr   1008,r4
c0013690:	7e 00 06 6c 	dssall
c0013694:	7c 00 04 ac 	hwsync
c0013698:	81 02 00 04 	lwz     r8,4(r2)
c001369c:	61 08 00 01 	ori     r8,r8,1
c00136a0:	91 02 00 04 	stw     r8,4(r2)
c00136a4:	7c e0 00 a6 	mfmsr   r7
c00136a8:	60 e7 80 00 	ori     r7,r7,32768
c00136ac:	64 e7 00 04 	oris    r7,r7,4
c00136b0:	7c 00 04 ac 	hwsync
c00136b4:	7c e0 01 24 	mtmsr   r7
c00136b8:	4c 00 01 2c 	isync
c00136bc:	4b ff ff f4 	b       c00136b0 <ppc6xx_idle+0xc4>

Thanks
Christophe

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

On 02/13/2020 02:28 PM, Larry Finger wrote:
> On 2/11/20 1:23 PM, Christophe Leroy wrote:
>> Can you send me a picture of that BUG Unable to handle kernel data 
>> access with all the registers values etc..., together with the 
>> matching vmlinux ?
>>
>> First thing is to identify where we are when that happens. That mean 
>> see what is at 0xc0013674. Can be done with 'ppc-linux-objdump -d 
>> vmlinux' (Or whatever your PPC objdump is named) and get the function 
>> code.
>>
>> Then we need to understand how we reach that function and why it tries 
>> to access a physical address.
>>
>>
>> Another thing I'm thinking about, not necessarily related to that 
>> problem: Some buggy drivers do DMA from stack. This doesn't work 
>> anymore with CONFIG_VMAP_STACK. Most of them can be detected with 
>> CONFIG_DEBUG_VIRTUAL so you should activate it.
> 
> Christophe,
> 
> The previous send of this message failed because the attached vmlinux 
> was too large.
> 
> I have gone about as far as I can in debugging the problem. Setting 
> CONFIG_DEBUG_VIRTUAL made no difference.
> 
> Attached are the final screenshot, and the patches that I have applied. 
> You already have the gzipped vmlinux.
> 

This screenshot makes more sense with the vmlinux you provided, problem 
at 0xc00136dc.

That's in function power_save_ppc32_restore() in 
arch/powerpc/kernel/idle_6xx.S.

c00136c0 <power_save_ppc32_restore>:
c00136c0:	81 2b 00 a0 	lwz     r9,160(r11)
c00136c4:	91 2b 00 90 	stw     r9,144(r11)
c00136c8:	39 60 00 00 	li      r11,0
c00136cc:	7d 30 fa a6 	mfspr   r9,1008
c00136d0:	75 29 00 40 	andis.  r9,r9,64
c00136d4:	41 82 00 18 	beq     c00136ec <power_save_ppc32_restore+0x2c>
c00136d8:	3d 2b 00 7c 	addis   r9,r11,124
 >> c00136dc:	81 29 92 5c 	lwz     r9,-28068(r9)
c00136e0:	7d 36 fb a6 	mtspr   1014,r9
c00136e4:	7c 00 04 ac 	hwsync
c00136e8:	4c 00 01 2c 	isync
c00136ec:	3d 2b 00 7c 	addis   r9,r11,124
c00136f0:	81 29 92 60 	lwz     r9,-28064(r9)
c00136f4:	7d 31 fb a6 	mtspr   1009,r9
c00136f8:	48 00 19 c4 	b       c00150bc <transfer_to_handler_cont>
c00136fc:	00 00 00 00 	.long 0x0

Can you try the change below (won't work anymore without 
CONFIG_VMAP_STACK, will fix it properly later when you confirm it is OK).

diff --git a/arch/powerpc/kernel/idle_6xx.S b/arch/powerpc/kernel/idle_6xx.S
index 0ffdd18b9f26..7be8a0f3fac8 100644
--- a/arch/powerpc/kernel/idle_6xx.S
+++ b/arch/powerpc/kernel/idle_6xx.S
@@ -166,7 +166,7 @@ BEGIN_FTR_SECTION
  	mfspr	r9,SPRN_HID0
  	andis.	r9,r9,HID0_NAP@h
  	beq	1f
-	addis	r9,r11,(nap_save_msscr0-KERNELBASE)@ha
+	addis	r9,r11,nap_save_msscr0@ha
  	lwz	r9,nap_save_msscr0@l(r9)
  	mtspr	SPRN_MSSCR0, r9
  	sync
@@ -174,7 +174,7 @@ BEGIN_FTR_SECTION
  1:
  END_FTR_SECTION_IFSET(CPU_FTR_NAP_DISABLE_L2_PR)
  BEGIN_FTR_SECTION
-	addis	r9,r11,(nap_save_hid1-KERNELBASE)@ha
+	addis	r9,r11,nap_save_hid1@ha
  	lwz	r9,nap_save_hid1@l(r9)
  	mtspr	SPRN_HID1, r9
  END_FTR_SECTION_IFSET(CPU_FTR_DUAL_PLL_750FX)


Thanks
Christophe

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Larry Finger]

[-- Attachment #1: Type: text/plain, Size: 381 bytes --]

Christophe,

With this patch, it gets further. Sometime after the boot process tries to start 
process init, it crashes with the unable to read data at 0x000157a0 with a 
faulting address of 0xc001683c. The screenshot is attached and the gzipped 
vmlinux is at http://www.lwfinger.com/download/vmlinux2.gz. The patches that 
were applied for this kernel are also attached,

Larry


[-- Attachment #2: PPC32_screenshot-2.jpg --]
[-- Type: image/jpeg, Size: 3465419 bytes --]

[-- Attachment #3: trial_patch2.patch --]
[-- Type: text/x-patch, Size: 1157 bytes --]

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3795654..3814960 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -214,7 +214,7 @@ transfer_to_handler_cont:
 	 * To speed up the syscall path where interrupts stay on, let's check
 	 * first if we are changing the MSR value at all.
 	 */
-	tophys(r12, r1)
+	tophys_novmstack r12 r1
 	lwz	r12,_MSR(r12)
 	andi.	r12,r12,MSR_EE
 	bne	1f
diff --git a/arch/powerpc/kernel/idle_6xx.S b/arch/powerpc/kernel/idle_6xx.S
index 0ffdd18..7be8a0f 100644
--- a/arch/powerpc/kernel/idle_6xx.S
+++ b/arch/powerpc/kernel/idle_6xx.S
@@ -166,7 +166,7 @@ BEGIN_FTR_SECTION
 	mfspr	r9,SPRN_HID0
 	andis.	r9,r9,HID0_NAP@h
 	beq	1f
-	addis	r9,r11,(nap_save_msscr0-KERNELBASE)@ha
+	addis	r9,r11,nap_save_msscr0@ha
 	lwz	r9,nap_save_msscr0@l(r9)
 	mtspr	SPRN_MSSCR0, r9
 	sync
@@ -174,7 +174,7 @@ BEGIN_FTR_SECTION
 1:
 END_FTR_SECTION_IFSET(CPU_FTR_NAP_DISABLE_L2_PR)
 BEGIN_FTR_SECTION
-	addis	r9,r11,(nap_save_hid1-KERNELBASE)@ha
+	addis	r9,r11,nap_save_hid1@ha
 	lwz	r9,nap_save_hid1@l(r9)
 	mtspr	SPRN_HID1, r9
 END_FTR_SECTION_IFSET(CPU_FTR_DUAL_PLL_750FX)

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

Larry,

Le 14/02/2020 à 00:09, Larry Finger a écrit :
> Christophe,
> 
> With this patch, it gets further. Sometime after the boot process tries 
> to start process init, it crashes with the unable to read data at 
> 0x000157a0 with a faulting address of 0xc001683c. The screenshot is 
> attached and the gzipped vmlinux is at 
> http://www.lwfinger.com/download/vmlinux2.gz. The patches that were 
> applied for this kernel are also attached,
> 


Did you try with the patch at https://patchwork.ozlabs.org/patch/1237387/ ?

I see the problem happens in kprobe_handler(). Can you try without 
CONFIG_KPROBE ?

Christophe

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

Le 14/02/2020 à 07:24, Christophe Leroy a écrit :
> Larry,
> 
> Le 14/02/2020 à 00:09, Larry Finger a écrit :
>> Christophe,
>>
>> With this patch, it gets further. Sometime after the boot process 
>> tries to start process init, it crashes with the unable to read data 
>> at 0x000157a0 with a faulting address of 0xc001683c. The screenshot is 
>> attached and the gzipped vmlinux is at 
>> http://www.lwfinger.com/download/vmlinux2.gz. The patches that were 
>> applied for this kernel are also attached,
>>
> 
> 
> Did you try with the patch at https://patchwork.ozlabs.org/patch/1237387/ ?
> 
> I see the problem happens in kprobe_handler(). Can you try without 
> CONFIG_KPROBE ?
> 

In fact, you hit two bugs. The first one is due to CONFIG_VMAP_STACK. 
The second one has always existed (at least since kernel source tree has 
been in git).

First bug is in function enter_rtas() which tries to read data on stack 
by using the linear physical address translation. This cannot be used 
with VM stack, it must re-enable data MMU translation to access data on 
the stack.

Second bug is in kprobe_handler() function, which does:

	if (*addr != BREAKPOINT_INSTRUCTION)

addr is the address where the 'trap' happened. When a trap happens with 
MMU disabled, addr contains the physical address of the trap. 
kprobe_handler() tries to read the instruction using physical address 
whereas MMU is enabled, so you get a bad access either because the said 
address is not mapped, or because access to userspace is not allowed.


Due to the first bug, you get a 'machine check', and as 
current->thread.rtas_sp has not been cleared yet, the machine check 
handler jumps to 'machine_check_in_rtas'.

machine_check_in_rtas does a trap, which in turn triggers the second bug.


Once the first bug is fixed, the second one should not popup.

Can you test patch https://patchwork.ozlabs.org/patch/1237929/ that 
fixes the first bug ?

Christophe

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Larry Finger]

On 2/14/20 12:24 AM, Christophe Leroy wrote:
> 
> Did you try with the patch at https://patchwork.ozlabs.org/patch/1237387/ ?

Christophe,

When I apply that patch, there is an error at

--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -301,6 +301,39 @@  MachineCheck:
  	. = 0x300
  	DO_KVM  0x300
  DataAccess:

It complains about "an attempt to move .org backwards".

Larry

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Larry Finger]

On 2/14/20 12:24 AM, Christophe Leroy wrote:
> 
> Did you try with the patch at https://patchwork.ozlabs.org/patch/1237387/ ?

Christophe,

When I apply that patch, there is an error at

--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -301,6 +301,39 @@  MachineCheck:
  	. = 0x300
  	DO_KVM  0x300
  DataAccess:

It complains about "an attempt to move .org backwards".

When I change the 0x300 to 0x310 in two places, it builds OK. Is that OK?

Larry

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

On 02/14/2020 06:24 PM, Larry Finger wrote:
> On 2/14/20 12:24 AM, Christophe Leroy wrote:
>>
>> Did you try with the patch at 
>> https://patchwork.ozlabs.org/patch/1237387/ ?
> 
> Christophe,
> 
> When I apply that patch, there is an error at
> 
> --- a/arch/powerpc/kernel/head_32.S
> +++ b/arch/powerpc/kernel/head_32.S
> @@ -301,6 +301,39 @@  MachineCheck:
>       . = 0x300
>       DO_KVM  0x300
>   DataAccess:
> 
> It complains about "an attempt to move .org backwards".
> 

Argh !

> When I change the 0x300 to 0x310 in two places, it builds OK. Is that OK?

No you can't do that.

The following should solve it for your case.

---
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 32875afb3319..f9941b766f63 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -270,6 +270,9 @@ __secondary_hold_acknowledge:
   * pointer when we take an exception from supervisor mode.)
   *	-- paulus.
   */
+#ifdef CONFIG_PPC_CHRP
+1:	b	machine_check_in_rtas
+#endif
  	. = 0x200
  	DO_KVM  0x200
  MachineCheck:
@@ -290,12 +293,9 @@ MachineCheck:
  7:	EXCEPTION_PROLOG_2
  	addi	r3,r1,STACK_FRAME_OVERHEAD
  #ifdef CONFIG_PPC_CHRP
-	bne	cr1,1f
+	bne	cr1,1b
  #endif
  	EXC_XFER_STD(0x200, machine_check_exception)
-#ifdef CONFIG_PPC_CHRP
-1:	b	machine_check_in_rtas
-#endif

  /* Data access exception. */
  	. = 0x300
---

Christophe

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Larry Finger]

Christophe,

On 2/14/20 1:35 PM, Christophe Leroy wrote:
> --- a/arch/powerpc/kernel/head_32.S
> +++ b/arch/powerpc/kernel/head_32.S
> @@ -270,6 +270,9 @@ __secondary_hold_acknowledge:
>    * pointer when we take an exception from supervisor mode.)
>    *    -- paulus.
>    */
> +#ifdef CONFIG_PPC_CHRP
> +1:    b    machine_check_in_rtas
> +#endif
>       . = 0x200
>       DO_KVM  0x200
>   MachineCheck:
> @@ -290,12 +293,9 @@ MachineCheck:
>   7:    EXCEPTION_PROLOG_2
>       addi    r3,r1,STACK_FRAME_OVERHEAD
>   #ifdef CONFIG_PPC_CHRP
> -    bne    cr1,1f
> +    bne    cr1,1b
>   #endif
>       EXC_XFER_STD(0x200, machine_check_exception)
> -#ifdef CONFIG_PPC_CHRP
> -1:    b    machine_check_in_rtas
> -#endif
> 
>   /* Data access exception. */
>       . = 0x300

With the above changes and all the other patches applied, the machine finally 
boots. It is so bloody slow that it takes a long time to do anything, but you 
finally got all the places that needed patches. I really lost track of how many 
bugs were fixed in the process, but I can now put that old box aside until time 
for v5.7.0-rc1. As you can tell, it only gets used to verify that PPC32 is 
working on real G4 hardware. It has no real value for any other function.

Thanks for the help,

Larry

Re: RESEND: Re: Problem booting a PowerBook G4 Aluminum after commit cd08f109 with CONFIG_VMAP_STACK=y

[Christophe Leroy]

Le 15/02/2020 à 03:42, Larry Finger a écrit :
> Christophe,
> 
> On 2/14/20 1:35 PM, Christophe Leroy wrote:
>> --- a/arch/powerpc/kernel/head_32.S
>> +++ b/arch/powerpc/kernel/head_32.S
>> @@ -270,6 +270,9 @@ __secondary_hold_acknowledge:
>>    * pointer when we take an exception from supervisor mode.)
>>    *    -- paulus.
>>    */
>> +#ifdef CONFIG_PPC_CHRP
>> +1:    b    machine_check_in_rtas
>> +#endif
>>       . = 0x200
>>       DO_KVM  0x200
>>   MachineCheck:
>> @@ -290,12 +293,9 @@ MachineCheck:
>>   7:    EXCEPTION_PROLOG_2
>>       addi    r3,r1,STACK_FRAME_OVERHEAD
>>   #ifdef CONFIG_PPC_CHRP
>> -    bne    cr1,1f
>> +    bne    cr1,1b
>>   #endif
>>       EXC_XFER_STD(0x200, machine_check_exception)
>> -#ifdef CONFIG_PPC_CHRP
>> -1:    b    machine_check_in_rtas
>> -#endif

I'll need to make it a bit different because it shoehorns into your 
config but won't fit if CONFIG_KVM_BOOK3S_32 is added.

>>
>>   /* Data access exception. */
>>       . = 0x300
> 
> With the above changes and all the other patches applied, the machine 
> finally boots. It is so bloody slow that it takes a long time to do 
> anything, but you finally got all the places that needed patches. I 
> really lost track of how many bugs were fixed in the process, but I can 
> now put that old box aside until time for v5.7.0-rc1. As you can tell, 
> it only gets used to verify that PPC32 is working on real G4 hardware. 
> It has no real value for any other function.

Yes, I don't have a G4 myself but this is so much nested with other 
stuff for the powerpc 83xx than we can't avoid the changes impacting the 
G4 and other hash-MMU based PPC32 allthough the changes I'm doing are 
not targetted at those platform at first. And as the 83xx is a 603 core, 
it is non-hash so all hash related things can't be verified. Plus all 
those small parts like power saving, RTAS, etc... which are more specific.
And checking with all possible options is also not easy.

VMAP-STACK was really a challenging functionnality, I'm happy it made 
its way to mainline though.

> 
> Thanks for the help,

Thanks to you for testing and for your patience.

Christophe