linux-kernel - Re: 答复: [PATCH] iommu/vt-d: Don't reject nvme host due to scope mismatch

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Message-ID: <bbff34ed-1c47-3eed-0bc9-30cfdd3ee90d@linux.intel.com>
Date:   Mon, 23 Dec 2019 21:05:22 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     "Jim,Yan" <jimyan@...du.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>
Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 答复: [PATCH] iommu/vt-d: Don't reject nvme host due to scope mismatch

Hi,

On 2019/12/23 15:59, Jim,Yan wrote:
>> -----邮件原件-----
>> 发件人: Jerry Snitselaar [mailto:jsnitsel@...hat.com]
>> 发送时间: 2019年12月20日 17:23
>> 收件人: Jim,Yan <jimyan@...du.com>
>> 抄送: joro@...tes.org; iommu@...ts.linux-foundation.org;
>> linux-kernel@...r.kernel.org
>> 主题: Re: [PATCH] iommu/vt-d: Don't reject nvme host due to scope mismatch
>>
>> On Fri Dec 20 19, jimyan wrote:
>>> On a system with an Intel PCIe port configured as a nvme host device,
>>> iommu initialization fails with
>>>
>>>     DMAR: Device scope type does not match for 0000:80:00.0
>>>
>>> This is because the DMAR table reports this device as having scope 2
>>> (ACPI_DMAR_SCOPE_TYPE_BRIDGE):
>>>
>>
>> Isn't that a problem to be fixed in the DMAR table then?
>>
>>> but the device has a type 0 PCI header:
>>> 80:00.0 Class 0600: Device 8086:2020 (rev 06)
>>> 00: 86 80 20 20 47 05 10 00 06 00 00 06 10 00 00 00
>>> 10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>> 20: 00 00 00 00 00 00 00 00 00 00 00 00 86 80 00 00
>>> 30: 00 00 00 00 90 00 00 00 00 00 00 00 00 01 00 00
>>>
>>> VT-d works perfectly on this system, so there's no reason to bail out
>>> on initialization due to this apparent scope mismatch. Add the class
>>> 0x600 ("PCI_CLASS_BRIDGE_HOST") as a heuristic for allowing DMAR
>>> initialization for non-bridge PCI devices listed with scope bridge.
>>>
>>> Signed-off-by: jimyan <jimyan@...du.com>
>>> ---
>>> drivers/iommu/dmar.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c index
>>> eecd6a421667..9faf2f0e0237 100644
>>> --- a/drivers/iommu/dmar.c
>>> +++ b/drivers/iommu/dmar.c
>>> @@ -244,6 +244,7 @@ int dmar_insert_dev_scope(struct
>> dmar_pci_notify_info *info,
>>> 		     info->dev->hdr_type != PCI_HEADER_TYPE_NORMAL) ||
>>> 		    (scope->entry_type == ACPI_DMAR_SCOPE_TYPE_BRIDGE &&
>>> 		     (info->dev->hdr_type == PCI_HEADER_TYPE_NORMAL &&
>>> +			  info->dev->class >> 8 != PCI_CLASS_BRIDGE_HOST &&
>>> 		      info->dev->class >> 8 != PCI_CLASS_BRIDGE_OTHER))) {
>>> 			pr_warn("Device scope type does not match for %s\n",
>>> 				pci_name(info->dev));
>>> --
>>> 2.11.0
>>>
>>> _______________________________________________
>>> iommu mailing list
>>> iommu@...ts.linux-foundation.org
>>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>>>
> Actually this patch is similar to the commit: ffb2d1eb88c3("iommu/vt-d: Don't reject NTB devices due to scope mismatch"). Besides, modifying DMAR table need OEM update BIOS. It is hard to implement.
>

For both cases, a quirk flag seems to be more reasonable, so that
unrelated devices will not be impacted.

Best regards,
baolu

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