From mboxrd@z Thu Jan  1 00:00:00 1970
From: msalter@redhat.com (Mark Salter)
Date: Tue, 04 Feb 2014 21:00:51 -0500
Subject: arm64: kernel panic in paging_init()
In-Reply-To: <34F26939-E85D-44DF-8E38-7B4AA4BF1A61@arm.com>
References: <1391460649.13327.51.camel@deneb.redhat.com>
 <20140204121452.GI30676@arm.com>
 <1391540244.18760.5.camel@deneb.redhat.com>
 <34F26939-E85D-44DF-8E38-7B4AA4BF1A61@arm.com>
Message-ID: <1391565651.18760.6.camel@deneb.redhat.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, 2014-02-04 at 22:39 +0000, Catalin Marinas wrote:
> On 4 Feb 2014, at 18:57, Mark Salter <msalter@redhat.com> wrote:
> > On Tue, 2014-02-04 at 12:14 +0000, Catalin Marinas wrote:
> >> On Mon, Feb 03, 2014 at 08:50:49PM +0000, Mark Salter wrote:
> >>> I'm seeing the following panic in paging init. This is on the foundation
> >>> model with a modified dtb memory node which has a non section-aligned
> >>> bank:
> >>> 	memory at 80000000 {
> >>> 		device_type = "memory";
> >>> 		reg = <0x00000000 0x80000000 0 0x20000000>,
> >>> 		      <0x00000000 0xa0300000 0 0x1fd00000>;
> >>> 	};
> >>> 
> >>> I only see this with 64k pagesize configured. What happens is the
> >>> non section-aligned bank causes alloc_init_pte() to allocate a page
> >>> for the new pte from the end of the first bank (the failing address
> >>> 0xfffffe001fff0000 [0x9fff0000 phys]). This should be a valid page
> >>> since it was mapped during the create_mapping() call for the first
> >>> memory bank. A flush_tlb_all() added to the end of create_mapping()
> >>> makes the panic go away so I think the problem is something stale
> >>> cached before the page with the failing address was mapped.
> >> 
> >> I think it goes like this:
> >> 
> >> head.S maps enough memory to get started but using 64K pages rather than
> >> 512M sections with a single pgd entry and several ptes. This never gets
> >> to the end of the first block (just up to KERNEL_END).
> >> 
> >> create_mapping() realises it can do a 512M section mapping, overriding
> >> the original table pgd entry with a block one. The memblock limit is set
> >> correctly PGDIR_SIZE but create_mapping, when it replaces the table pgd
> >> with a block one doesn't do any TLB invalidation.
> >> 
> >> So I wouldn't do a TLB invalidation all the time but only when the old
> >> pmd was set. Please give the patch below a try, I only compiled it (I'll
> >> add some text afterwards):
> > 
> > Yes, that works. Thanks.
> 
> Can I add your tested-by?

Yes, you may.