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

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Date:   Mon, 23 Dec 2019 07:59:11 +0000
From:   "Jim,Yan" <jimyan@...du.com>
To:     Jerry Snitselaar <jsnitsel@...hat.com>
CC:     "joro@...tes.org" <joro@...tes.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: 答复: [PATCH] iommu/vt-d: Don't reject nvme host due to scope mismatch

> -----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.

Jim

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