linux-kernel - Re: [Patch Part3 V5 5/8] iommu/vt-d: Enhance intel_irq_remapping driver to support DMAR unit hotplug

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Date:	Tue, 16 Sep 2014 16:13:47 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Yijing Wang <wangyijing@...wei.com>,
	Joerg Roedel <joro@...tes.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Vinod Koul <vinod.koul@...el.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
CC:	Ashok Raj <ashok.raj@...el.com>, Tony Luck <tony.luck@...el.com>,
	iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
	linux-hotplug@...r.kernel.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org
Subject: Re: [Patch Part3 V5 5/8] iommu/vt-d: Enhance intel_irq_remapping
 driver to support DMAR unit hotplug



On 2014/9/16 15:53, Yijing Wang wrote:
> On 2014/9/16 15:00, Jiang Liu wrote:
>> On 2014/9/15 10:20, Yijing Wang wrote:
>>>> +static void ir_remove_ioapic_hpet_scope(struct intel_iommu *iommu)
>>>> +{
>>>> +	int i;
>>>>  
>>>> -			ir_parse_one_hpet_scope(scope, iommu);
>>>> -		}
>>>> -		start += scope->length;
>>>> -	}
>>>> +	for (i = 0; i < MAX_HPET_TBS; i++)
>>>> +		if (ir_hpet[i].iommu == iommu)
>>>> +			ir_hpet[i].iommu = NULL;
>>>
>>> Hi Gerry, why not reset whole ir_hpe and ir_ioapic data struct?
>> Hi Yijing,
>> 	Thanks for review. Zero is legal for id, bus and devfn in
>> struct ioapic_scope and struct hpet_scope. So we use domain field
>> as a flag to mark entry valid or invalid and only reset iommu field.
> 
> Hi Gerry, use iommu field as a flag to mark entry valid may be not safe enough,
> I found map_hpet_to_ir() and map_ioapic_to_ir() still only check the id field to return the valid iommu.
> 
> What about this case:
> E.g. ir_hpet[2].id = N, ir_hpet[2].iommu = NULL, ir_hpet[4].id = N, ir_hpet[4].iommu = iommu;
> 
> ir_hpet[2] maybe released yet, and the hpet now has been saved in ir_hpet[4], but map_hpet_to_irq()
> will return the wrong iommu(NULL).
Hi Yijing,
Good catch, I will enhance map_hpet_to_ir() and map_ioapic_to_ir().
Regards!
Gerry
> 
> 
> static struct intel_iommu *map_hpet_to_ir(u8 hpet_id)
> {
> 	int i;
> 
> 	for (i = 0; i < MAX_HPET_TBS; i++)
> 		if (ir_hpet[i].id == hpet_id)
> 			return ir_hpet[i].iommu;
> 	return NULL;
> }
> 
>>
>> Regards!
>> Gerry
>>>
>>>
>>>
>>>>  
>>>> -	return 0;
>>>> +	for (i = 0; i < MAX_IO_APICS; i++)
>>>> +		if (ir_ioapic[i].iommu == iommu)
>>>> +			ir_ioapic[i].iommu = NULL;
>>>>  }
>>>>  
>>>
>>> --
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>>
>> .
>>
> 
> 
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