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Message-ID: <5e18c60e-9572-5844-b17d-aa55e7ff4709@c-s.fr>
Date: Wed, 19 Dec 2018 07:03:32 +0000
From: Christophe Leroy <christophe.leroy@....fr>
To: Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] powerpc: implement CONFIG_DEBUG_VIRTUAL
On 12/19/2018 06:57 AM, Christophe Leroy wrote:
>
>
> Le 19/12/2018 à 01:26, Michael Ellerman a écrit :
>> Michael Ellerman <mpe@...erman.id.au> writes:
>>> Christophe Leroy <christophe.leroy@....fr> writes:
>>>
>>>> This patch implements CONFIG_DEBUG_VIRTUAL to warn about
>>>> incorrect use of virt_to_phys() and page_to_phys()
>>>
>>> This commit is breaking my p5020ds booting a 32-bit kernel with:
>>>
>>> smp: Bringing up secondary CPUs ...
>>> __ioremap(): phys addr 0x7fef5000 is RAM lr ioremap_coherent
>>> Unable to handle kernel paging request for data at address 0x00000000
>>> Faulting instruction address: 0xc002e950
>>> Oops: Kernel access of bad area, sig: 11 [#1]
>>> BE SMP NR_CPUS=24 CoreNet Generic
>>> Modules linked in:
>>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted
>>> 4.20.0-rc2-gcc-7.0.1-00138-g9a0380d299e9 #148
>>> NIP: c002e950 LR: c002eb20 CTR: 00000001
>>> REGS: e804bd20 TRAP: 0300 Not tainted
>>> (4.20.0-rc2-gcc-7.0.1-00138-g9a0380d299e9)
>>> MSR: 00021002 <CE,ME> CR: 28004222 XER: 00000000
>>> DEAR: 00000000 ESR: 00000000
>>> GPR00: c002eb20 e804bdd0 e8050000 00000000 00021002 00000000
>>> 00000050 00021002
>>> GPR08: 2d3f0000 00000001 00000000 00000004 24000842 00000000
>>> c00026d0 00000000
>>> GPR16: 00000000 00000000 00000000 00000000 00000000 00000000
>>> 00000000 00000001
>>> GPR24: 00029002 7fef5140 30000000 00000000 00000000 00000040
>>> 00000001 00000000
>>> NIP [c002e950] smp_85xx_kick_cpu+0x120/0x410
>>> LR [c002eb20] smp_85xx_kick_cpu+0x2f0/0x410
>>> Call Trace:
>>> [e804bdd0] [c002eb20] smp_85xx_kick_cpu+0x2f0/0x410 (unreliable)
>>> [e804be20] [c0012e38] __cpu_up+0xc8/0x230
>>> [e804be50] [c0040b34] bringup_cpu+0x34/0x110
>>> [e804be70] [c00418a8] cpu_up+0x128/0x250
>>> [e804beb0] [c0b84b14] smp_init+0xc4/0x10c
>>> [e804bee0] [c0b75c1c] kernel_init_freeable+0xc8/0x250
>>> [e804bf20] [c00026e8] kernel_init+0x18/0x120
>>> [e804bf40] [c0011298] ret_from_kernel_thread+0x14/0x1c
>>> Instruction dump:
>>> 7fb3e850 57bdd1be 2e1d0000 41d20250 57bd3032 393dffc0 7e6a9b78
>>> 5529d1be
>>> 39290001 7d2903a6 60000000 60000000 <7c0050ac> 394a0040 4200fff8
>>> 7c0004ac
>>> ---[ end trace edcab2a1dfd5b38c ]---
>>>
>>>
>>> Which is obviously this hunk:
>>>
>>>> diff --git a/arch/powerpc/mm/pgtable_32.c
>>>> b/arch/powerpc/mm/pgtable_32.c
>>>> index 4fc77a99c9bf..68d204a45cd0 100644
>>>> --- a/arch/powerpc/mm/pgtable_32.c
>>>> +++ b/arch/powerpc/mm/pgtable_32.c
>>>> @@ -143,7 +143,7 @@ __ioremap_caller(phys_addr_t addr, unsigned long
>>>> size, pgprot_t prot, void *call
>>>> * Don't allow anybody to remap normal RAM that we're using.
>>>> * mem_init() sets high_memory so only do the check after that.
>>>> */
>>>> - if (slab_is_available() && (p < virt_to_phys(high_memory)) &&
>>>> + if (slab_is_available() && virt_addr_valid(p) &&
>>>> page_is_ram(__phys_to_pfn(p))) {
>>>> printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
>>>> (unsigned long long)p, __builtin_return_address(0));
>>>
>>>
>>> I'll try and come up with a fix tomorrow.
>>
>> Actually I think that change is just wrong. virt_addr_valid() takes a
>> virtual address, but p is a physical address.
>>
>> So I'll drop this hunk for now, which makes the patch a no-op when
>> DEBUG_VIRTUAL is n which is probably the way it should be.
>
> The hunk is obviously wrong for sure. Anyway there's a problem, most
> likely high_memory is not a valid virtual address, so without this hunk
> I get the following warning at every ioremap():
>
> [ 0.000000] WARNING: CPU: 0 PID: 0 at
> ./arch/powerpc/include/asm/io.h:809 __ioremap_caller+0x9c/0x180
> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
> 4.20.0-rc6-s3k-dev-00677-g9c98dcab6203-dirty #615
> [ 0.000000] NIP: c000fcd0 LR: c000fc64 CTR: 00000000
> [ 0.000000] REGS: c073de50 TRAP: 0700 Not tainted
> (4.20.0-rc6-s3k-dev-00677-g9c98dcab6203-dirty)
> [ 0.000000] MSR: 00021032 <ME,IR,DR,RI> CR: 28944422 XER: 0000f940
> [ 0.000000]
> [ 0.000000] GPR00: c000fe04 c073df00 c06e1450 00000001 00004023
> c073df38 c0018f50 00000001
> [ 0.000000] GPR08: 00002000 08000000 00002000 00000000 88944224
> 00600000 00000000 07ff9580
> [ 0.000000] GPR16: 00000000 07ffb94c 00000000 00000000 00000000
> 00000000 00000000 00000000
> [ 0.000000] GPR24: 00000000 c0760000 0000019f ff000000 ff000000
> c000fe04 00004000 c0018f50
> [ 0.000000] NIP [c000fcd0] __ioremap_caller+0x9c/0x180
> [ 0.000000] LR [c000fc64] __ioremap_caller+0x30/0x180
> [ 0.000000] Call Trace:
> [ 0.000000] [c073df00] [c02fc23c] of_address_to_resource+0x114/0x154
> (unreliable)
> [ 0.000000] [c073df30] [c000fe04] ioremap_wt+0x20/0x30
> [ 0.000000] [c073df40] [c0018f50] mpc8xx_pic_init+0x70/0xf8
> [ 0.000000] [c073df80] [c0655b84] mpc8xx_pics_init+0x10/0x6c
> [ 0.000000] [c073df90] [c0675080] cmpc885_pics_init+0x14/0x118
> [ 0.000000] [c073dfa0] [c0652eb0] init_IRQ+0x24/0x38
> [ 0.000000] [c073dfb0] [c0650b10] start_kernel+0x2a8/0x3d4
> [ 0.000000] [c073dff0] [c0002258] start_here+0x44/0x98
> [ 0.000000] Instruction dump:
> [ 0.000000] 419e00b8 7f83e378 480013fd 7c7d1b79 41820030 576304be
> 7c63ea14 80010034
> [ 0.000000] bb410018 7c0803a6 38210030 4e800020 <0fe00000> 7f9c4840
> 409cffc4 480000a8
> [ 0.000000] random: get_random_bytes called from
> print_oops_end_marker+0x60/0x84 with crng_init=0
> [ 0.000000] ---[ end trace 25d7f28ce013ad37 ]---
>
> I'll try and come with solution during the day.
In fact the solution is the following:
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 4fc77a99c9bf..60401af2bc8f 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -143,7 +143,7 @@ __ioremap_caller(phys_addr_t addr, unsigned long
size, pgprot_t prot, void *call
* Don't allow anybody to remap normal RAM that we're using.
* mem_init() sets high_memory so only do the check after that.
*/
- if (slab_is_available() && (p < virt_to_phys(high_memory)) &&
+ if (slab_is_available() && (p <= virt_to_phys(high_memory - 1)) &&
page_is_ram(__phys_to_pfn(p))) {
printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
(unsigned long long)p, __builtin_return_address(0));
I'll send an updated patch in a few minutes.
Christophe
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