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From: Mike Rapoport <rppt@linux.ibm.com>
To: Tony Lindgren <tony@atomide.com>
Cc: Mike Rapoport <rppt@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Russell King <linux@armlinux.org.uk>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-omap@vger.kernel.org, regressions@lists.linux.dev
Subject: Re: [PATCH v2 3/3] arm: extend pfn_valid to take into accound freed memory map alignment
Date: Tue, 29 Jun 2021 13:50:35 +0300	[thread overview]
Message-ID: <YNr6+wOiR7/Yx9M1@linux.ibm.com> (raw)
In-Reply-To: <YNrfqtBpKsNj033w@atomide.com>

Hi,

On Tue, Jun 29, 2021 at 11:54:02AM +0300, Tony Lindgren wrote:
> Hi,
> 
> * Mike Rapoport <rppt@linux.ibm.com> [210629 05:33]:
> > On Mon, Jun 28, 2021 at 06:26:26PM +0300, Tony Lindgren wrote:
> > > * Mike Rapoport <rppt@linux.ibm.com> [210628 14:07]:
> > > > Can you please send log with 'memblock=debug' added to the command line?
> > > 
> > > Sure, log now available at:
> > > 
> > > http://muru.com/beagle-x15.txt
> > 
> > Hmm, no clues yet :(
> > 
> > Do you have CONFIG_DEBUG_VM, CONFIG_DEBUG_VM_PGFLAGS and
> > CONFIG_PAGE_POISONING enabled in your config?
> > If not, can you please enable them and see if any of VM_BUG_* triggers?
> 
> OK enabled, and no errors or warnings are triggered.
> 
> > Do you use FLATMEM or SPARSEMEM in your config?
> 
> Looks like make omap2plus_defconfig enables FLATMEM:
> 
> $ grep -e SPARSEMEM -e FLATMEM .config
> CONFIG_ARCH_FLATMEM_ENABLE=y
> CONFIG_ARCH_SPARSEMEM_ENABLE=y
> CONFIG_FLATMEM_MANUAL=y
> # CONFIG_SPARSEMEM_MANUAL is not set
> CONFIG_FLATMEM=y
> 
> > Let's try seeing what PFNs get false results from pfn_valid, maybe this
> > will give a better lead.
> 
> With your patch below, system boots with lots of the following:
> 
> [   13.058654] Freeing unused kernel image (initmem) memory: 1024K
> ...
> [   13.129211] pfn_valid(__sync_icache_dcache+0x2c/0x138): pfn: fffb6: is_map: 1 overlaps: 0
> [   13.137481] pfn_valid(__sync_icache_dcache+0x2c/0x138): pfn: fffb7: is_map: 1 overlaps: 0

...

> Then changing console loglevel to 0 boots system to login prompt. But I'm
> seeing some init processes segfaulting during start-up.

As it seems, the new version of pfn_valid() decides that last pages are not
valid because of the overflow in memblock_overlaps_region(). As the result,
__sync_icache_dcache() skips flushing these pages.

The patch below should fix this. I've left the prints for now, hopefully
they will not appear anymore. 

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 6162a070a410..7ba22d23eca4 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -126,10 +126,16 @@ int pfn_valid(unsigned long pfn)
 {
 	phys_addr_t addr = __pfn_to_phys(pfn);
 	unsigned long pageblock_size = PAGE_SIZE * pageblock_nr_pages;
+	bool overlaps = memblock_overlaps_region(&memblock.memory,
+				     ALIGN_DOWN(addr, pageblock_size),
+				     pageblock_size - 1);
 
 	if (__phys_to_pfn(addr) != pfn)
 		return 0;
 
+	if (memblock_is_map_memory(addr) != overlaps)
+		pr_info("%s(%pS): pfn: %lx: is_map: %d overlaps: %d\n", __func__, (void *)_RET_IP_, pfn, memblock_is_map_memory(addr), overlaps);
+
 	/*
 	 * If address less than pageblock_size bytes away from a present
 	 * memory chunk there still will be a memory map entry for it
@@ -137,7 +143,7 @@ int pfn_valid(unsigned long pfn)
 	 */
 	if (memblock_overlaps_region(&memblock.memory,
 				     ALIGN_DOWN(addr, pageblock_size),
-				     pageblock_size))
+				     pageblock_size - 1))
 		return 1;
 
 	return 0;
 
-- 
Sincerely yours,
Mike.

  reply	other threads:[~2021-06-29 10:51 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-19 14:14 [PATCH v2 0/3] memblock, arm: fixes for freeing of the memory map Mike Rapoport
2021-05-19 14:14 ` [PATCH v2 1/3] memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER Mike Rapoport
2021-05-19 14:14 ` [PATCH v2 2/3] memblock: align freed memory map on pageblock boundaries with SPARSEMEM Mike Rapoport
2021-05-19 14:14 ` [PATCH v2 3/3] arm: extend pfn_valid to take into accound freed memory map alignment Mike Rapoport
2021-06-28 10:20   ` Tony Lindgren
2021-06-28 13:16     ` Mike Rapoport
2021-06-28 15:26       ` Tony Lindgren
2021-06-29  5:33         ` Mike Rapoport
2021-06-29  8:54           ` Tony Lindgren
2021-06-29 10:50             ` Mike Rapoport [this message]
2021-06-29 11:52               ` Tony Lindgren
2021-06-29 12:50                 ` Mike Rapoport
2021-06-29 12:53                   ` Tony Lindgren
2021-06-30  7:20                   ` Mike Rapoport
2021-05-20  6:21 ` [PATCH v2 0/3] memblock, arm: fixes for freeing of the memory map Kefeng Wang

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