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Date:   Thu, 9 Sep 2021 11:36:23 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To:     Will Deacon <will@kernel.org>
Cc:     kernel test robot <oliver.sang@intel.com>,
        Claire Chang <tientzu@chromium.org>,
        Christoph Hellwig <hch@lst.de>,
        Stefano Stabellini <sstabellini@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org,
        lkp@intel.com
Subject: Re: [swiotlb]  461021875c: EIP:__dma_direct_alloc_pages
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 <20210909150428.GA10436@willie-the-truck>
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On Thu, Sep 09, 2021 at 04:04:29PM +0100, Will Deacon wrote:
> On Wed, Sep 08, 2021 at 04:52:39PM +0800, kernel test robot wrote:
> > FYI, we noticed the following commit (built with gcc-9):
> > 
> > commit: 461021875c5057b3a408db0aa91b15119064ffa8 ("swiotlb: Add restricted DMA pool initialization")
> > https://git.kernel.org/cgit/linux/kernel/git/konrad/swiotlb.git devel/for-linus-5.14
> > 
> > 
> > in testcase: boot
> > 
> > on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> > 
> > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > 
> > 
> > 
> > If you fix the issue, kindly add following tag
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> > 
> > 
> > [  157.633812][    T1] BUG: kernel NULL pointer dereference, address: 00000046
> > [  157.636589][    T1] #PF: supervisor read access in kernel mode
> > [  157.637641][    T1] #PF: error_code(0x0000) - not-present page
> > [  157.637641][    T1] *pde = 00000000
> > [  157.643000][    T1] Oops: 0000 [#1] SMP
> > [  157.643000][    T1] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W         5.12.0-rc3-00029-g461021875c50 #1
> > [  157.643000][    T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> > [  157.650987][    T1] EIP: __dma_direct_alloc_pages+0xee/0x280
> > [  157.650987][    T1] Code: d2 f6 c1 20 0f 94 c0 0f 95 c2 d3 e0 d3 e2 83 c0 ff 83 d2 ff 39 f0 89 d0 19 f8 0f 92 c0 0f b6 c0 8d 44 40 01 8b 93 c0 02 00 00 <80> 7a 46 00 74 6c 8b 7d ec 89 d8 89 fa e8 c0 34 00 00 89 c6 85 c0
> > [  157.658987][    T1] EAX: 00000004 EBX: c2713884 ECX: 00000018 EDX: 00000000
> > [  157.658987][    T1] ESI: ffffffff EDI: 00000000 EBP: c1c43d2c ESP: c1c43d10
> > [  157.658987][    T1] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010297
> > [  157.666985][    T1] CR0: 80050033 CR2: 00000046 CR3: 1b1da000 CR4: 000406d0
> > [  157.666985][    T1] Call Trace:
> > [  157.666985][    T1]  dma_direct_alloc+0x50/0x180
> > [  157.674977][    T1]  dma_alloc_attrs+0x69/0xc0
> > [  157.674977][    T1]  ide_allocate_dma_engine+0x55/0x80
> 
> This IDE code doesn't exist upstream any more. See b7fb14d3ac63 ("ide: remove
> the legacy ide driver").

Let me kill that branch since we never pushed that to Linus.
> 
> Will