Re: [PATCH v3] powerpc: implement CONFIG_DEBUG_VIRTUAL

[Christophe Leroy]

Le 19/12/2018 Ã 01:26, Michael Ellerman a ÃcritÂ:
> Michael Ellerman <mpe@xxxxxxxxxxxxxx> writes:
> > Christophe Leroy <christophe.leroy@xxxxxx> 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.

Christophe

> cheers