linux-kernel - Re: [PATCH 3/5 v2] iommu/vt-d: Do deferred attachment in iommu_need

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Date:   Tue, 18 Feb 2020 19:54:52 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     David Woodhouse <dwmw2@...radead.org>, jroedel@...e.de,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5 v2] iommu/vt-d: Do deferred attachment in
 iommu_need_mapping()

Hi Joerg,

On 2020/2/18 17:28, Joerg Roedel wrote:
> Hi Baolu,
> 
> On Tue, Feb 18, 2020 at 10:38:14AM +0800, Lu Baolu wrote:
>>> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
>>> index 42cdcce1602e..32f43695a22b 100644
>>> --- a/drivers/iommu/intel-iommu.c
>>> +++ b/drivers/iommu/intel-iommu.c
>>> @@ -2541,9 +2541,6 @@ static void do_deferred_attach(struct device *dev)
>>>    static struct dmar_domain *deferred_attach_domain(struct device *dev)
>>>    {
>>> -	if (unlikely(attach_deferred(dev)))
>>> -		do_deferred_attach(dev);
>>> -
>>
>> This should also be moved to the call place of deferred_attach_domain()
>> in bounce_map_single().
>>
>> bounce_map_single() assumes that devices always use DMA domain, so it
>> doesn't call iommu_need_mapping(). We could do_deferred_attach() there
>> manually.
> 
> Good point, thanks for your review. Updated patch below.
> 

Looks good to me now. For all patches in this series,

Acked-by: Lu Baolu <baolu.lu@...ux.intel.com>

Best regards,
baolu

>  From 3a5b8a66d288d86ac1fd45092e7d96f842d0cccf Mon Sep 17 00:00:00 2001
> From: Joerg Roedel <jroedel@...e.de>
> Date: Mon, 17 Feb 2020 17:20:59 +0100
> Subject: [PATCH 3/5] iommu/vt-d: Do deferred attachment in
>   iommu_need_mapping()
> 
> The attachment of deferred devices needs to happen before the check
> whether the device is identity mapped or not. Otherwise the check will
> return wrong results, cause warnings boot failures in kdump kernels, like
> 
> 	WARNING: CPU: 0 PID: 318 at ../drivers/iommu/intel-iommu.c:592 domain_get_iommu+0x61/0x70
> 
> 	[...]
> 
> 	 Call Trace:
> 	  __intel_map_single+0x55/0x190
> 	  intel_alloc_coherent+0xac/0x110
> 	  dmam_alloc_attrs+0x50/0xa0
> 	  ahci_port_start+0xfb/0x1f0 [libahci]
> 	  ata_host_start.part.39+0x104/0x1e0 [libata]
> 
> With the earlier check the kdump boot succeeds and a crashdump is written.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>   drivers/iommu/intel-iommu.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 42cdcce1602e..723f615c6e84 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -2541,9 +2541,6 @@ static void do_deferred_attach(struct device *dev)
>   
>   static struct dmar_domain *deferred_attach_domain(struct device *dev)
>   {
> -	if (unlikely(attach_deferred(dev)))
> -		do_deferred_attach(dev);
> -
>   	return find_domain(dev);
>   }
>   
> @@ -3595,6 +3592,9 @@ static bool iommu_need_mapping(struct device *dev)
>   	if (iommu_dummy(dev))
>   		return false;
>   
> +	if (unlikely(attach_deferred(dev)))
> +		do_deferred_attach(dev);
> +
>   	ret = identity_mapping(dev);
>   	if (ret) {
>   		u64 dma_mask = *dev->dma_mask;
> @@ -3958,7 +3958,11 @@ bounce_map_single(struct device *dev, phys_addr_t paddr, size_t size,
>   	int prot = 0;
>   	int ret;
>   
> +	if (unlikely(attach_deferred(dev)))
> +		do_deferred_attach(dev);
> +
>   	domain = deferred_attach_domain(dev);
> +
>   	if (WARN_ON(dir == DMA_NONE || !domain))
>   		return DMA_MAPPING_ERROR;
>   
>