Re: linux-next: powerpc le qemu boot failure after merge of the akpm tree

From: Andrey Konovalov
Date: Thu Jan 31 2019 - 08:50:56 EST

On Thu, Jan 31, 2019 at 8:40 AM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
>
> (added Andrey Konovalov)
>
> On Thu, Jan 31, 2019 at 07:15:26AM +0100, Christophe Leroy wrote:
> >
> > Le 31/01/2019 Ã 07:06, Stephen Rothwell a Ãcrit :
> > >Hi all,
> > >
> > >On Thu, 31 Jan 2019 16:38:54 +1100 Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
> > >>
> > >>[I am guessing that is is something in Andrew's tree that has caused
> > >>this.]
> > >>
> > >>My qemu boot of the powerpc pseries_le_defconfig config failed like this:
> > >>
> > >>htab_hash_mask = 0x1ffff
> > >>-----------------------------------------------------
> > >>numa: NODE_DATA [mem 0x7ffe7000-0x7ffebfff]
> > >>Kernel panic - not syncing: sparse_buffer_init: Failed to allocate 2147483648 bytes align=0x10000 nid=0 from=fffffffffffffff
> > >>CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc4 #2
> > >>Call Trace:
> > >>[c00000000105bbd0] [c000000000b1345c] dump_stack+0xb0/0xf4 (unreliable)
> > >>[c00000000105bc10] [c000000000111120] panic+0x168/0x3b8
> > >>[c00000000105bcb0] [c000000000e701c8] sparse_init_nid+0x178/0x550
> > >>[c00000000105bd70] [c000000000e709b4] sparse_init+0x210/0x238
> > >>[c00000000105bdb0] [c000000000e468f4] initmem_init+0x1e0/0x260
> > >>[c00000000105be80] [c000000000e3b9b0] setup_arch+0x354/0x3d4
> > >>[c00000000105bef0] [c000000000e33afc] start_kernel+0x98/0x648
> > >>[c00000000105bf90] [c00000000000b270] start_here_common+0x1c/0x52c
> > >
> > >A quick bisect leads to this:
> > >
> > >1c3c9328cde027eb875ba4692f0a5d66b0afe862 is the first bad commit
> > >commit 1c3c9328cde027eb875ba4692f0a5d66b0afe862
> > >Author: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > >Date: Thu Jan 31 10:51:32 2019 +1100
> > >
> > > treewide: add checks for the return value of memblock_alloc*()
> > > Add check for the return value of memblock_alloc*() functions and call
> > > panic() in case of error. The panic message repeats the one used by
> > > panicing memblock allocators with adjustment of parameters to include only
> > > relevant ones.
> > >
> > >Which is just adding the panic we hit. So, presumably, the bug is in a
> > >preceding patch :-(
> > >
> > >I have left the kernel not booting for today.
> > >
> >
> > No I think the error is really in that patch, see my other mail.
> >
> > See https://elixir.bootlin.com/linux/v5.0-rc4/source/mm/memblock.c#L1455,
> > memblock_alloc_try_nid_raw() is not supposed to panic, so the last hunk of
> > this patch should be reverted.
> >
> > Found in total three problematic hunks in that patch:
> >
> > @@ -48,6 +53,11 @@ static phys_addr_t __init kasan_alloc_raw_page(int node)
> > void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
> > __pa(MAX_DMA_ADDRESS),
> > MEMBLOCK_ALLOC_KASAN, node);
> > + if (!p)
> > + panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%llx\n",
> > + __func__, PAGE_SIZE, PAGE_SIZE, node,
> > + __pa(MAX_DMA_ADDRESS));
> > +
> > return __pa(p);
> > }
>
> I've looked more closely to the code that uses this function and it does
> not seem to handle allocation error.
> I can replace the panic with WARN(), but I think that panic() here is
> appropriate.
>
> Andrey, can you comment?

+ Andrey Ryabinin

I think panic() there looks appropriate. Added Andrey Ryabinin to take a look.

>
>
> > @@ -211,6 +211,9 @@ static int __init iob_init(struct device_node *dn)
> > iob_l2_base = memblock_alloc_try_nid_raw(1UL << 21, 1UL << 21,
> > MEMBLOCK_LOW_LIMIT, 0x80000000,
> > NUMA_NO_NODE);
> > + if (!iob_l2_base)
> > + panic("%s: Failed to allocate %lu bytes align=0x%lx max_addr=%x\n",
> > + __func__, 1UL << 21, 1UL << 21, 0x80000000);
> >
> > pr_info("IOBMAP L2 allocated at: %p\n", iob_l2_base);
>
> This one is actually fixes my own mistake from one of the previous patches
> that converted memblock_alloc_base() to memblock_alloc_try_nid_raw() without
> adding the panic() (commit 47e382eb08cfa0199c4ea9f9cc73f1b48a3a4b1d
> "powerpc: prefer memblock APIs returning virtual address")
>
> > @@ -425,6 +436,10 @@ static void __init sparse_buffer_init(unsigned long
> > size, int nid)
> > memblock_alloc_try_nid_raw(size, PAGE_SIZE,
> > __pa(MAX_DMA_ADDRESS),
> > MEMBLOCK_ALLOC_ACCESSIBLE, nid);
> > + if (!sparsemap_buf)
> > + panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%lx\n",
> > + __func__, size, PAGE_SIZE, nid, __pa(MAX_DMA_ADDRESS));
> > +
> > sparsemap_buf_end = sparsemap_buf + size;
> > }
>
> This hunk was not needed as sparse can deal with this allocation failure.
>
> Andrew, can you please add the below patch to as a fixup to "treewide: add
> checks for the return value of memblock_alloc*()"?
>
> From 854f54b9d4fe52f477765b905a4b2c421d30f46e Mon Sep 17 00:00:00 2001
> From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Date: Thu, 31 Jan 2019 09:18:50 +0200
> Subject: [PATCH] mm/sparse: don't panic if the allocation in
> sparse_buffer_init fails
>
> Addition of panic if memblock_alloc_try_nid_raw() call in
> sparse_buffer_init() fails was over enthusiastic as the system is perfectly
> capable to deal with that allocation failure.
> Remove the panic().
>
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> ---
> mm/sparse.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 1471f06..c11aba0 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -434,10 +434,6 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
> memblock_alloc_try_nid_raw(size, PAGE_SIZE,
> __pa(MAX_DMA_ADDRESS),
> MEMBLOCK_ALLOC_ACCESSIBLE, nid);
> - if (!sparsemap_buf)
> - panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%lx\n",
> - __func__, size, PAGE_SIZE, nid, __pa(MAX_DMA_ADDRESS));
> -
> sparsemap_buf_end = sparsemap_buf + size;
> }
>
> --
> 2.7.4
>