Re: [PATCH v2 3/3] arm: extend pfn_valid to take into accound freed memory map alignment

From: Tony Lindgren <tony@atomide.com>
To: Mike Rapoport <rppt@linux.ibm.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 14:52:39 +0300	[thread overview]
Message-ID: <YNsJh7trg4up5l26@atomide.com> (raw)
In-Reply-To: <YNr6+wOiR7/Yx9M1@linux.ibm.com>

* Mike Rapoport <rppt@linux.ibm.com> [210629 10:51]:
> 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. 

Yes this allows the system to boot for me :)

I'm still seeing these three prints though:

...
smp: Brought up 1 node, 2 CPUs
SMP: Total of 2 processors activated (3994.41 BogoMIPS).
CPU: All CPU(s) started in SVC mode.
pfn_valid(__pageblock_pfn_to_page+0x14/0xa8): pfn: afe00: is_map: 0 overlaps: 1
pfn_valid(__pageblock_pfn_to_page+0x28/0xa8): pfn: affff: is_map: 0 overlaps: 1
pfn_valid(__pageblock_pfn_to_page+0x38/0xa8): pfn: afe00: is_map: 0 overlaps: 1
devtmpfs: initialized
...

Regards,

Tony

> 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.