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 15:53:31 +0800
From:	Yijing Wang <wangyijing@...wei.com>
To:	Jiang Liu <jiang.liu@...ux.intel.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 15:00, 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).


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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>>
> 
> .
> 


-- 
Thanks!
Yijing

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