Re: Dom0 kernel panic when porting xen to new arm soc

[Julien Grall <julien.grall@citrix.com>]

On 20/06/15 15:47, Peng Fan wrote:
> On 6/20/2015 10:08 PM, Peng Fan wrote:
>> Hi Julien,
>>
>> On 6/20/2015 6:19 PM, Julien Grall wrote:
>>> Hi,
>>>
>>> On 19/06/2015 14:22, Peng Fan wrote:
>>>> diff --git a/kernel/timer.c b/kernel/timer.c
>>>> index 38f0d40..4a025cc 100644
>>>> --- a/kernel/timer.c
>>>> +++ b/kernel/timer.c
>>>> @@ -1175,6 +1175,10 @@ static inline void __run_timers(struct tvec_base
>>>> *base)
>>>>
>>>>                          base->running_timer = timer;
>>>>                          detach_expired_timer(timer, base);
>>>> +                       if (!fn) {
>>>> +                               printk("fn is null why????\n"); ---->
>>>> This log only shows once. Not sure why fn is null and only once.
>>>> +                               continue;
>>>> +                       }
>>>>
>>>>                          if (irqsafe) {
>>>>                                  spin_unlock(&base->lock);
>>>
>>> By any chance, does your board has a another timer (i.e other than the
>>> generic timer)?
>>
>> Yeah. There is a another timer whose rating is lower that generic timer.
>>>
>>> I would also track down to see who is adding this timer.
>>>
>>>> But after apply the above kernel patch, Dom0 Linux can handle shell
>>>> input.
>>>> Just have another question, How can Dom0 handle DMA for arm.
>>>
>>> When Xen is allocating the RAM bank for DOM0 we use a direct mapping
>>> (i.e the Physical Address = Intermediate Address for the RAM). So DOM0
>>> can perform DMA as on baremetal.
>> Thanks. Current, without using rootfs in sd card, my Dom0 kernel can
>> boot using ramfs. But if with sdhc which use ADMA, Dom0 kernel will
>> panic. Below is the log:
>>
>> sdhci: Secure Digital Host Controller Interface driver
>> sdhci: Copyright(c) Pierre Ossman
>> sdhci-pltfm: SDHCI platform and OF driver helper
>> Unable to handle kernel NULL pointer dereference at virtual address 00000000
>> pgd = 80004000
>> [00000000] *pgd=00000000
>> Internal error: Oops: 5 [#1] PREEMPT SMP ARM
>> Modules linked in:
>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.14.38-02383-g5ccf32b-dirty #22
>> task: 84074000 ti: 84078000 task.ti: 84078000
>> PC is at bitmap_clear+0xc0/0xdc
>> LR is at bitmap_clear+0x54/0xdc
>> pc : [<8029deb8>]    lr : [<8029de4c>]    psr: 20000193
>> sp : 84079d80  ip : 00000001  fp : 00000000
>> r10: 00077fff  r9 : 00000404  r8 : 00000001
>> r7 : 00000001  r6 : 00000001  r5 : 00000000  r4 : ffffffff
>> r3 : 00000001  r2 : 00000001  r1 : 20000193  r0 : 00000015
>> Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
>> Control: 10c53c7d  Table: 8800406a  DAC: 00000015
>> Process swapper/0 (pid: 1, stack limit = 0x84078238)
>> Stack: (0x84079d80 to 0x8407a000)
>> 9d80: 80000113 00000000 87efa000 81109918 00001000 800197f8 84128558
>> 00080008
>> 9da0: 84079dec 000000d0 84bfeac0 84126c10 84126c10 ffffffff 00000404
>> ffffffff
>> 9dc0: 00000000 00000402 00000000 00000000 84126c10 80310ba8 ffffffff
>> 00000000
>> 9de0: 00000000 00000524 84078000 00000000 00000000 ffffffff ffffffff
>> 84bfeac0
>> 9e00: 84bfe800 8000b407 07eb0000 8116e0f8 00000000 804ee81c ffffffff
>> ffffffff
>> 9e20: 00000000 84126c10 84c92010 84bfeac0 00000000 84126c10 84126c00
>> 84bfeac0
>> 9e40: 84078030 804f08e4 804f03d8 84126c10 fffffdfb 8115401c 8115401c
>> 00000000
>> 9e60: 0000010f 80362330 803622ec 84126c10 811c8098 00000000 8115401c
>> 80360b1c
>> 9e80: 84126c10 8115401c 84126c44 00000000 80de1888 80360d28 00000000
>> 8115401c
>> 9ea0: 80360c9c 8035f10c 8406965c 84123634 8115401c 84c8bf80 8112f3c8
>> 803602bc
>> 9ec0: 80d08314 8115401c 00000006 8115401c 00000006 8116e080 8116e080
>> 8036130c
>> 9ee0: 00000000 80e00f78 00000006 800088dc 8400f900 80c94fe0 840bd480
>> 80735184
>> 9f00: 00000000 8116e080 0000150c 8012d430 00000000 811105b0 60000113
>> 00000001
>> 9f20: 87ffc576 8075ca38 0000010f 8004b0f0 80d66884 00000006 87ffc583
>> 00000006
>> 9f40: 811105a0 80e00f78 00000006 8116e080 8116e080 80da150c 0000010f
>> 80df4154
>> 9f60: 80df4148 80da1c4c 00000006 00000006 80da150c 9355553c 84079f9c
>> 80731338
>> 9f80: 00000000 00000000 80727254 00000000 00000000 00000000 00000000
>> 00000000
>> 9fa0: 00000000 8072725c 00000000 8000ecf8 00000000 00000000 00000000
>> 00000000
>> 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>> 00000000
>> 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 9355553c
>> 9355553c
>> [<8029deb8>] (bitmap_clear) from [<800197f8>]
>> (__arm_dma_free.isra.18+0xe4/0x228)
>> [<800197f8>] (__arm_dma_free.isra.18) from [<80310ba8>]
>> (xen_swiotlb_free_coherent+0xfc/0x140)
>> [<80310ba8>] (xen_swiotlb_free_coherent) from [<804ee81c>]
>> (sdhci_add_host+0xb34/0xe64)
>> [<804ee81c>] (sdhci_add_host) from [<804f08e4>]
>> (sdhci_esdhc_imx_probe+0x50c/0x808)
>> [<804f08e4>] (sdhci_esdhc_imx_probe) from [<80362330>]
>> (platform_drv_probe+0x44/0xa4)
>> [<80362330>] (platform_drv_probe) from [<80360b1c>]
>> (driver_probe_device+0x120/0x25c)
>> [<80360b1c>] (driver_probe_device) from [<80360d28>]
>> (__driver_attach+0x8c/0x90)
>> [<80360d28>] (__driver_attach) from [<8035f10c>]
>> (bus_for_each_dev+0x60/0x94)
>> [<8035f10c>] (bus_for_each_dev) from [<803602bc>]
>> (bus_add_driver+0x148/0x1f0)
>> [<803602bc>] (bus_add_driver) from [<8036130c>] (driver_register+0x78/0xf8)
>> [<8036130c>] (driver_register) from [<800088dc>]
>> (do_one_initcall+0xf8/0x144)
>> [<800088dc>] (do_one_initcall) from [<80da1c4c>]
>> (kernel_init_freeable+0x138/0x1d8)
>> [<80da1c4c>] (kernel_init_freeable) from [<8072725c>] (kernel_init+0x8/0xf0)
>> [<8072725c>] (kernel_init) from [<8000ecf8>] (ret_from_fork+0x14/0x3c)
>> Code: 10866003 1206601f 10633006 11e02312 (e5953000)
>> ---[ end trace f6f103bb73cc0503 ]---
>> note: swapper/0[1] exited with preempt_count 1
>> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>>
>> The piece code is at here:
>> if (host->flags & SDHCI_USE_ADMA) {
>>          /*
>>           * We need to allocate descriptors for all sg entries
>>           * (128) and potentially one alignment transfer for
>>           * each of those entries.
>>           */
>>          host->adma_desc = dma_alloc_coherent(mmc_dev(host->mmc),
>>                                               ADMA_SIZE, &host->adma_addr,
>>                                               GFP_KERNEL);
>>          host->align_buffer = kmalloc(128 * 4, GFP_KERNEL);
>>          printk("%p %p\n", host->adma_desc, host->align_buffer); --->
>> Here host->adma_desc is NULL
>>          if (!host->adma_desc || !host->align_buffer) {
>>                  dma_free_coherent(mmc_dev(host->mmc), ADMA_SIZE,
>> -->Trigger panic
>>                                    host->adma_desc, host->adma_addr);
>>                  kfree(host->align_buffer);
>>
>> So dma_alloc_coherent failed, dma_free_coherent-->bitmap_clear trigger
>> Dom0 panic. 128M memory is for Dom0, dma_alloc_coherent should not fail.
>> Do you have any suggestions?
>>

Adding Stefano as he worked on DMA/swiotlb for ARM.

> Another problem comes to me, with 128M for Dom0, Dom0 can printk msg to
> serial, but with "dom0_mem=1024M", I see nothing from serial for Dom0.

Well, the RAM bank will surely be different between the 2 configurations.

The DOM0 may have crashed before the console has effectively setup for
multiple reason.
Can you try this hacky patch [1], it will print everything using the Xen
console.

[1] http://lists.xen.org/archives/html/xen-devel/2014-10/msg03436.html

Regards,

-- 
Julien Grall