IOMMU breakage on arm64 (was: Re: dma-direct: implement complete bus_dma_mask handling)

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Christoph Hellwig <hch@lst.de>, Will Deacon <will.deacon@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Joerg Roedel <joro@8bytes.org>,
	Magnus Damm <magnus.damm@gmail.com>
Cc: Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux IOMMU <iommu@lists.linux-foundation.org>
Subject: IOMMU breakage on arm64 (was: Re: dma-direct: implement complete bus_dma_mask handling)
Date: Tue, 6 Nov 2018 20:44:07 +0100	[thread overview]
Message-ID: <CAMuHMdUosqWTn5yDjGMWrLpWEyZfxtGWYfqmenYVqE8g7HEt7Q@mail.gmail.com> (raw)
In-Reply-To: <git-mailbomb-linux-master-b4ebe6063204da58e48600b810a97c29ae9e5d12@kernel.org>

Hi Christoph et al,

On Tue, Oct 23, 2018 at 1:40 AM Linux Kernel Mailing List
<linux-kernel@vger.kernel.org> wrote:
> Commit:     b4ebe6063204da58e48600b810a97c29ae9e5d12
> Parent:     7d21ee4c719f00896767ce19c4c01a56374c2ced
> Refname:    refs/heads/master
> Web:        https://git.kernel.org/torvalds/c/b4ebe6063204da58e48600b810a97c29ae9e5d12
> Author:     Christoph Hellwig <hch@lst.de>
> AuthorDate: Thu Sep 20 14:04:08 2018 +0200
> Committer:  Christoph Hellwig <hch@lst.de>
> CommitDate: Mon Oct 1 07:28:03 2018 -0700
>
>     dma-direct: implement complete bus_dma_mask handling
>
>     Instead of rejecting devices with a too small bus_dma_mask we can handle
>     by taking the bus dma_mask into account for allocations and bounce
>     buffering decisions.
>
>     Signed-off-by: Christoph Hellwig <hch@lst.de>

I  have bisected the following crash to the above commit:

    ipmmu-vmsa e67b0000.mmu: Cannot accommodate DMA translation for
IOMMU page tables
    sata_rcar ee300000.sata: Unable to initialize IPMMU context
    iommu: Failed to add device ee300000.sata to group 0: -22
    Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000038
    Mem abort info:
      ESR = 0x96000004
      Exception class = DABT (current EL), IL = 32 bits
      SET = 0, FnV = 0
      EA = 0, S1PTW = 0
    Data abort info:
      ISV = 0, ISS = 0x00000004
      CM = 0, WnR = 0
    [0000000000000038] user address but active_mm is swapper
    Internal error: Oops: 96000004 [#1] PREEMPT SMP
    CPU: 2 PID: 51 Comm: kworker/2:1 Not tainted
4.20.0-rc1-arm64-renesas-dirty #74
    Hardware name: Renesas Salvator-X 2nd version board based on
r8a7795 ES2.0+ (DT)
    Workqueue: events deferred_probe_work_func
    pstate: 60000005 (nZCv daif -PAN -UAO)
    pc : ipmmu_domain_free+0x1c/0xa0
    lr : ipmmu_domain_free+0x14/0xa0
    sp : ffff000009c9b990
    x29: ffff000009c9b990 x28: 0000000000000000
    x27: ffff000008dff000 x26: 0000000000000000
    x25: ffff000008dd9000 x24: 0000000000000014
    x23: ffff8006fffdbb20 x22: ffff000008dff000
    x21: ffff8006f898e680 x20: ffff8006f8fa6c00
    x19: ffff8006f8fa6c08 x18: 0000000000000037
    x17: 0000000000000020 x16: ffff000008a8f780
    x15: ffff8006fb096f10 x14: ffff8006f93731c8
    x13: 0000000000000000 x12: ffff8006fb096f10
    x11: ffff8006f9372fe8 x10: ffff000008dff708
    x9 : ffff8006fb096f50 x8 : ffff000008dff708
    x7 : ffff0000089f1858 x6 : 0000000000000000
    x5 : 0000000000000000 x4 : ffff8006f89a3000
    x3 : 00008006f7131000 x2 : ffff8006fb2b5700
    x1 : 0000000000000000 x0 : 0000000000000028
    Process kworker/2:1 (pid: 51, stack limit = 0x(____ptrval____))
    Call trace:
     ipmmu_domain_free+0x1c/0xa0
     iommu_group_release+0x48/0x68
     kobject_put+0x74/0xe8
     kobject_del.part.0+0x3c/0x50
     kobject_put+0x60/0xe8
     iommu_group_get_for_dev+0xa8/0x1f0
     ipmmu_add_device+0x1c/0x40
     of_iommu_configure+0x118/0x190
     of_dma_configure+0xcc/0x1f0
     platform_dma_configure+0x18/0x28
     really_probe+0x94/0x2a8
     driver_probe_device+0x58/0x100
     __device_attach_driver+0x90/0xd0
     bus_for_each_drv+0x64/0xc8
     __device_attach+0xd8/0x130
     device_initial_probe+0x10/0x18
     bus_probe_device+0x98/0xa0
     deferred_probe_work_func+0x74/0xb0
     process_one_work+0x294/0x6f0
     worker_thread+0x238/0x460
     kthread+0x120/0x128
     ret_from_fork+0x10/0x1c
    Code: aa0003f3 97ffeb1a d1002274 f85f8261 (f9401c20)
    ---[ end trace 4c46c7fd7cd07245 ]---

Reproducing on v4.20-rc1 requires CONFIG_IPMMU_VMSA=y, and whitelisting
SATA for IOMMU use (https://patchwork.kernel.org/patch/10544059/).
For older versions you also have to backport commit 3a0832d093693ede ("arm64:
dts: renesas: salvator-xs: enable SATA").

Actually there are two issues at hand:

1) drivers/iommu/io-pgtable-arm.c:__arm_lpae_alloc_pages() allocates
   memory (above 4 GiB) and maps it for DMA use, but it is rejected due
   to:

       dma_map_single(dev, pages, size, DMA_TO_DEVICE) != virt_to_phys(pages)

> --- a/include/linux/dma-direct.h
> +++ b/include/linux/dma-direct.h
> @@ -27,7 +27,8 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
>         if (!dev->dma_mask)
>                 return false;
>
> -       return addr + size - 1 <= *dev->dma_mask;
> +       return addr + size - 1 <=
> +               min_not_zero(*dev->dma_mask, dev->bus_dma_mask);

       *dev->dma_mask = 0xffffffffff (40-bit)
       dev->bus_dma_mask = 0xffffffff (32-bit)

   Hence before, we had (in __arm_lpae_alloc_pages()):

       arm-lpae io-pgtable: pages = ffff8006f88f3000
       arm-lpae io-pgtable: dma = 0x00000007388f3000
       arm-lpae io-pgtable: virt_to_phys(pages) = 0x00000007388f3000

   After this change, we have:

       arm-lpae io-pgtable: pages = ffff8006f882b000
       arm-lpae io-pgtable: dma = 0x0000000074009000
       arm-lpae io-pgtable: virt_to_phys(pages) = 0x000000073882b000

   And SATA runs without using the IOMMU.

2) The Renesas IPMMU driver doesn't handle the above failure well,
   leading to a NULL pointer dereference.
   This can be fixed using the (gmail-whitespace-damaged) patch below:

--- a/drivers/iommu/ipmmu-vmsa.c
+++ b/drivers/iommu/ipmmu-vmsa.c
@@ -635,7 +635,8 @@ static void ipmmu_domain_free(struct iommu_domain
*io_domain)
         * been detached.
         */
        iommu_put_dma_cookie(io_domain);
-       ipmmu_domain_destroy_context(domain);
+       if (domain->mmu)
+               ipmmu_domain_destroy_context(domain);
        free_io_pgtable_ops(domain->iop);
        kfree(domain);
 }

   I expect drivers/iommu/arm-smmu-v3.c and drivers/iommu/arm-smmu.c
   need similar fixes.
   I didn't check all drivers, but e.g. drivers/iommu/amd_iommu.c has
a similar check.

Does the IOMMU work on other arm64 platforms in v4.20-rc1?

Thanks for your comments!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
