From: Baolu Lu <baolu.lu@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: baolu.lu@linux.intel.com, Vasant Hegde <vasant.hegde@amd.com>,
Matt Fagnani <matt.fagnani@bell.net>,
Thorsten Leemhuis <regressions@leemhuis.info>,
Joerg Roedel <jroedel@suse.de>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
LKML <linux-kernel@vger.kernel.org>,
"regressions@lists.linux.dev" <regressions@lists.linux.dev>,
Linux PCI <linux-pci@vger.kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [regression, bisected, pci/iommu] Bug 216865 - Black screen when amdgpu started during 6.2-rc1 boot with AMD IOMMU enabled
Date: Tue, 10 Jan 2023 13:28:31 +0800 [thread overview]
Message-ID: <ae78b813-34f2-da61-e6c6-f4985c5b6641@linux.intel.com> (raw)
In-Reply-To: <Y7wZ+SvT455HS2b6@nvidia.com>
On 2023/1/9 21:43, Jason Gunthorpe wrote:
> On Sat, Jan 07, 2023 at 10:44:46AM +0800, Baolu Lu wrote:
>> On 1/6/2023 10:14 PM, Jason Gunthorpe wrote:
>>> On Thu, Jan 05, 2023 at 03:57:28PM +0530, Vasant Hegde wrote:
>>>> Matt,
>>>>
>>>> On 1/5/2023 6:39 AM, Matt Fagnani wrote:
>>>>> I built 6.2-rc2 with the patch applied. The same black screen problem happened
>>>>> with 6.2-rc2 with the patch. I tried to use early kdump with 6.2-rc2 with the
>>>>> patch twice by panicking the kernel with sysrq+alt+c after the black screen
>>>>> happened. The system rebooted after about 10-20 seconds both times, but no kdump
>>>>> and dmesg files were saved in /var/crash. I'm attaching the lspci -vvv output as
>>>>> requested.
>>>>>
>>>>
>>>> Thanks for testing. As mentioned earlier I was not expecting this patch to fix
>>>> the black screen issue. It should fix kernel warnings and IOMMU page fault
>>>> related call traces. By any chance do you have the kernel boot logs?
>>>>
>>>>
>>>> @Baolu,
>>>> Looking into lspci output, it doesn't list ACS feature for Graphics card. So
>>>> with your fix it didn't enable PASID and hence it failed to boot.
>>>
>>> The ACS checks being done are feature of the path not the end point or
>>> root port.
>>>
>>> If we are expecting ACS on the end port then it is just a bug in how
>>> the test was written.. The test should be a NOP because there are no
>>> switches in this topology.
>>>
>>> Looking at it, this seems to just be because pci_enable_pasid is
>>> calling pci_acs_path_enabled wrong, the only other user is here:
>>>
>>> for (bus = pdev->bus; !pci_is_root_bus(bus); bus = bus->parent) {
>>> if (!bus->self)
>>> continue;
>>>
>>> if (pci_acs_path_enabled(bus->self, NULL, REQ_ACS_FLAGS))
>>> break;
>>>
>>> pdev = bus->self;
>>>
>>> group = iommu_group_get(&pdev->dev);
>>> if (group)
>>> return group;
>>> }
>>>
>>> And notice it is calling it on pdev->bus not on pdev itself which
>>> naturally excludes the end point from the ACS validation.
>>>
>>> So try something like:
>>>
>>> if (!pci_acs_path_enabled(pdev->bus->self, NULL, PCI_ACS_RR | PCI_ACS_UF))
>>>
>>> (and probably need to check for null ?)
>>
>> Yeah! This really is a misuse of pci_acs_path_enabled().
>>
>> But if @pdev is an endpoint of a multiple function device, perhaps we
>> still need to check acs on it?
>
> Ah, I don't know anything about what this means from a spec
> perspective.
>
> Certainly if a function can internalize MMIO and loop it back to
> another function then it surely is not OK for PASID either, nor should
> those functions be in different iommu groups.
>
> So, either this never happens for some spec reason, or the test in the
> iommu code forming groups is incorrect.
The pci_device_group() path handles this like below:
/*
* For multifunction devices which are not isolated from each other, find
* all the other non-isolated functions and look for existing groups. For
* each function, we also need to look for aliases to or from other devices
* that may already have a group.
*/
static struct iommu_group *get_pci_function_alias_group(struct pci_dev
*pdev,
unsigned long
*devfns)
{
struct pci_dev *tmp = NULL;
struct iommu_group *group;
if (!pdev->multifunction || pci_acs_enabled(pdev, REQ_ACS_FLAGS))
return NULL;
It seems that all devices of an MFD shares a single iommu group if
there lacks ACS control.
--
Best regards,
baolu
next prev parent reply other threads:[~2023-01-10 5:28 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-30 8:18 [regression, bisected, pci/iommu] Bug 216865 - Black screen when amdgpu started during 6.2-rc1 boot with AMD IOMMU enabled Thorsten Leemhuis
2023-01-03 10:30 ` Joerg Roedel
2023-01-03 19:06 ` Matt Fagnani
[not found] ` <5aa0e698-f715-0481-36e5-46505024ebc1@bell.net>
2023-01-04 6:54 ` Baolu Lu
2023-01-04 15:50 ` Vasant Hegde
2023-01-05 1:09 ` Matt Fagnani
2023-01-05 10:27 ` Vasant Hegde
2023-01-05 10:37 ` Baolu Lu
2023-01-05 10:46 ` Vasant Hegde
2023-01-05 14:46 ` Deucher, Alexander
2023-01-05 15:27 ` Felix Kuehling
2023-01-06 5:48 ` Baolu Lu
2023-02-15 15:39 ` Bjorn Helgaas
2023-02-16 0:35 ` Felix Kuehling
2023-02-16 0:44 ` Jason Gunthorpe
2023-02-16 5:37 ` Vasant Hegde
2023-02-16 14:55 ` Felix Kuehling
2023-02-16 14:53 ` Felix Kuehling
2023-02-16 5:25 ` Vasant Hegde
2023-02-16 18:59 ` Matt Fagnani
2023-02-16 19:59 ` Felix Kuehling
2023-02-17 5:36 ` Vasant Hegde
2023-02-17 5:23 ` Vasant Hegde
2023-01-05 19:51 ` Matt Fagnani
2023-01-06 7:28 ` Matt Fagnani
2023-01-10 16:08 ` Vasant Hegde
2023-01-10 16:12 ` Vasant Hegde
2023-01-06 14:14 ` Jason Gunthorpe
2023-01-07 2:44 ` Baolu Lu
2023-01-09 13:43 ` Jason Gunthorpe
2023-01-10 5:28 ` Baolu Lu [this message]
2023-01-10 5:48 ` Baolu Lu
2023-01-10 8:06 ` Matt Fagnani
[not found] ` <bb3d5d1a-c222-9270-60fa-7d0b74bebd1a@linux.intel.com>
2023-01-10 22:12 ` Matt Fagnani
2023-01-10 13:25 ` Jason Gunthorpe
2023-01-10 13:45 ` Christian König
2023-01-10 13:51 ` Jason Gunthorpe
2023-01-10 13:56 ` Christian König
2023-01-10 20:51 ` Matt Fagnani
2023-01-11 8:35 ` Christian König
2023-01-10 15:05 ` Felix Kuehling
2023-01-10 15:19 ` Jason Gunthorpe
2023-01-10 15:21 ` Felix Kuehling
2023-01-11 3:16 ` Baolu Lu
2023-01-11 13:08 ` Jason Gunthorpe
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