* [PATCH] IOMMU/VT-d: Fix iommu=no-igfx if the IOMMU scope contains phantom device
@ 2023-02-26 0:08 Marek Marczykowski-Górecki
2023-02-27 16:55 ` Jan Beulich
0 siblings, 1 reply; 2+ messages in thread
From: Marek Marczykowski-Górecki @ 2023-02-26 0:08 UTC (permalink / raw
To: xen-devel; +Cc: Marek Marczykowski-Górecki, Kevin Tian
If the scope for IGD's IOMMU contains additional device that doesn't
actually exist, iommu=no-igfx would not disable that IOMMU. In this
particular case (Thinkpad x230) it included
00:02.1, but there is no such device on this platform.
Consider only existing devices for "gfx only" check.
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
I have looked at existence check acpi_parse_one_drhd(), but re-using
that one wouldn't work for two reasons:
- gfx_only logic is very much tied to acpi_parse_dev_scope()
- pci_device_detect() in acpi_parse_one_drhd() is skipped in case of
(implicit or explicit) iommu=force
---
xen/drivers/passthrough/vtd/dmar.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/xen/drivers/passthrough/vtd/dmar.c b/xen/drivers/passthrough/vtd/dmar.c
index 78c8bad1515a..3b5e152901b9 100644
--- a/xen/drivers/passthrough/vtd/dmar.c
+++ b/xen/drivers/passthrough/vtd/dmar.c
@@ -396,6 +396,7 @@ static int __init acpi_parse_dev_scope(
igd_drhd_address = drhd->address;
if ( gfx_only &&
+ pci_device_detect(seg, bus, path->dev, path->fn) &&
pci_conf_read8(PCI_SBDF(seg, bus, path->dev, path->fn),
PCI_CLASS_DEVICE + 1) != 0x03
/* PCI_BASE_CLASS_DISPLAY */ )
--
2.39.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] IOMMU/VT-d: Fix iommu=no-igfx if the IOMMU scope contains phantom device
2023-02-26 0:08 [PATCH] IOMMU/VT-d: Fix iommu=no-igfx if the IOMMU scope contains phantom device Marek Marczykowski-Górecki
@ 2023-02-27 16:55 ` Jan Beulich
0 siblings, 0 replies; 2+ messages in thread
From: Jan Beulich @ 2023-02-27 16:55 UTC (permalink / raw
To: Marek Marczykowski-Górecki; +Cc: Kevin Tian, xen-devel
On 26.02.2023 01:08, Marek Marczykowski-Górecki wrote:
> If the scope for IGD's IOMMU contains additional device that doesn't
> actually exist, iommu=no-igfx would not disable that IOMMU. In this
> particular case (Thinkpad x230) it included
> 00:02.1, but there is no such device on this platform.
> Consider only existing devices for "gfx only" check.
>
Hmm, perhaps
Fixes: 2d7f191b392e ('VT-d: generalize and correct "iommu=no-igfx" handling')
?
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> ---
> I have looked at existence check acpi_parse_one_drhd(), but re-using
> that one wouldn't work for two reasons:
> - gfx_only logic is very much tied to acpi_parse_dev_scope()
I think this one could be dealt with, but ...
> - pci_device_detect() in acpi_parse_one_drhd() is skipped in case of
> (implicit or explicit) iommu=force
... I agree this is a good reason to put the check in acpi_parse_dev_scope().
> --- a/xen/drivers/passthrough/vtd/dmar.c
> +++ b/xen/drivers/passthrough/vtd/dmar.c
> @@ -396,6 +396,7 @@ static int __init acpi_parse_dev_scope(
> igd_drhd_address = drhd->address;
>
> if ( gfx_only &&
> + pci_device_detect(seg, bus, path->dev, path->fn) &&
> pci_conf_read8(PCI_SBDF(seg, bus, path->dev, path->fn),
> PCI_CLASS_DEVICE + 1) != 0x03
> /* PCI_BASE_CLASS_DISPLAY */ )
If we're adding an existence check, then maybe better in the surrounding
if(): Setting igd_drhd_address when there's not really a device at the
designated address isn't very sensible either. (In fact I think I'm going
to alter the inner part of that if() again as well.)
Jan
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-02-26 0:08 [PATCH] IOMMU/VT-d: Fix iommu=no-igfx if the IOMMU scope contains phantom device Marek Marczykowski-Górecki
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