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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] iommu/amd-vi: do not error if device referenced in IVMD is not behind any IOMMU
On Tue, Oct 08, 2024 at 04:01:28PM +0200, Jan Beulich wrote:
> On 08.10.2024 12:47, Roger Pau Monne wrote:
> > IVMD table contains restrictions about memory which must be mandatory
> > assigned
> > to devices (and which permissions it should use), or memory that should be
> > never accessible to devices.
> >
> > Some hardware however contains ranges in IVMD that reference devices
> > outside of
> > the IVHD tables (in other words, devices not behind any IOMMU). Such
> > mismatch
> > will cause Xen to fail in register_range_for_device(), ultimately leading to
> > the IOMMU being disabled, and Xen crashing as x2APIC support might be
> > already
> > enabled and relying on the IOMMU functionality.
>
> I find it hard to believe that on x86 systems with IOMMUs some devices would
> be left uncovered by any IOMMU. Is it possible that IVHD is flawed there? In
> which case we might rightfully refuse to boot? (Can you share e.g. that
> "iommu=debug" output that results from parsing the tables on that system?)
I'm afraid I don't have any of such systems to test myself, however I
have the contents of IVRS:
ACPI Table Header
------------------------------------------------------------------
Signature : IVRS
Length : 0x000001F8
Revision : 0x02
Checksum : 0x06
OEM ID : AMD
OEM Table ID : AmdTable
OEM Revision : 0x00000001
Creator ID : AMD
Creator Revision : 0x00000001
IVinfo : 0x00203043
IVHD
----------------------------------------------------------------
Type : 0x10
Flags : 0xB0
Length : 0x0044
IOMMU Device ID : 0x0002
Capability Offset : 0x0040
IOMMU Base Address : 0x00000000FD200000
Segment Group : 0x0000
IOMMU Info : 0x0000
IOMMU Feature Info : 0x80048F6E
Range
--------------------------------------------------
Type : 0x03
Start of Range : 0x0003
End of Range : 0xFFFE
DTE Setting : 0x00
Alias Range
--------------------------------------------------
Type : 0x43
Start of Range : 0xFF00
End of Range : 0xFFFF
DTE Setting : 0x00
Source Device ID : 0x00A5
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0x00
Source Device ID : 0x00A0
Handle : 0x00
Variety : HPET
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0xD7
Source Device ID : 0x00A0
Handle : 0x21
Variety : IOAPIC
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0x00
Source Device ID : 0x0001
Handle : 0x22
Variety : IOAPIC
IVHD
----------------------------------------------------------------
Type : 0x11
Flags : 0x30
Length : 0x0054
IOMMU Device ID : 0x0002
Capability Offset : 0x0040
IOMMU Base Address : 0x00000000FD200000
Segment Group : 0x0000
IOMMU Info : 0x0000
IOMMU Feature Info : 0x00048000
Range
--------------------------------------------------
Type : 0x03
Start of Range : 0x0003
End of Range : 0xFFFE
DTE Setting : 0x00
Alias Range
--------------------------------------------------
Type : 0x43
Start of Range : 0xFF00
End of Range : 0xFFFF
DTE Setting : 0x00
Source Device ID : 0x00A5
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0x00
Source Device ID : 0x00A0
Handle : 0x00
Variety : HPET
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0xD7
Source Device ID : 0x00A0
Handle : 0x21
Variety : IOAPIC
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0x00
Source Device ID : 0x0001
Handle : 0x22
Variety : IOAPIC
IVMD
----------------------------------------------------------------
Type : 0x22
Flags : 0x08
Length : 0x0020
DeviceID : 0x0000
AuxiliaryData : 0x0FFF
Reserved : 0x0000000000000000
IVMD Start Address : 0x0000000096191000
IVMD Memory Block Length : 0x0000000000000022
IVMD
----------------------------------------------------------------
Type : 0x22
Flags : 0x08
Length : 0x0020
DeviceID : 0x0000
AuxiliaryData : 0x0FFF
Reserved : 0x0000000000000000
IVMD Start Address : 0x0000000097D9E000
IVMD Memory Block Length : 0x0000000000000022
IVMD
----------------------------------------------------------------
Type : 0x22
Flags : 0x08
Length : 0x0020
DeviceID : 0x0000
AuxiliaryData : 0x0FFF
Reserved : 0x0000000000000000
IVMD Start Address : 0x0000000097D9D000
IVMD Memory Block Length : 0x0000000000000022
IVHD
----------------------------------------------------------------
Type : 0x40
Flags : 0x30
Length : 0x00D0
IOMMU Device ID : 0x0002
Capability Offset : 0x0040
IOMMU Base Address : 0x00000000FD200000
Segment Group : 0x0000
IOMMU Info : 0x0000
IOMMU Feature Info : 0x00048000
Range
--------------------------------------------------
Type : 0x03
Start of Range : 0x0003
End of Range : 0xFFFE
DTE Setting : 0x00
Alias Range
--------------------------------------------------
Type : 0x43
Start of Range : 0xFF00
End of Range : 0xFFFF
DTE Setting : 0x00
Source Device ID : 0x00A5
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0x00
Source Device ID : 0x00A0
Handle : 0x00
Variety : HPET
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0xD7
Source Device ID : 0x00A0
Handle : 0x21
Variety : IOAPIC
Special Device
--------------------------------------------------
Type : 0x48
Device ID : 0x0000
DTE Setting : 0x00
Source Device ID : 0x0001
Handle : 0x22
Variety : IOAPIC
Variable Length ACPI HID Device
--------------------------------------------------
Type : 0xF0
Device ID : 0x00A5
DTE Setting : 0x40
Hardware ID : AMDI0020
Extended DTE Setting :
Unique ID Format : 2
Unique ID Length : 9
Unique ID : \_SB.FUR0
Variable Length ACPI HID Device
--------------------------------------------------
Type : 0xF0
Device ID : 0x00A5
DTE Setting : 0x40
Hardware ID : AMDI0020
Extended DTE Setting :
Unique ID Format : 2
Unique ID Length : 9
Unique ID : \_SB.FUR1
Variable Length ACPI HID Device
--------------------------------------------------
Type : 0xF0
Device ID : 0x00A5
DTE Setting : 0x40
Hardware ID : AMDI0020
Extended DTE Setting :
Unique ID Format : 2
Unique ID Length : 9
Unique ID : \_SB.FUR2
Variable Length ACPI HID Device
--------------------------------------------------
Type : 0xF0
Device ID : 0x00A5
DTE Setting : 0x40
Hardware ID : AMDI0020
Extended DTE Setting :
Unique ID Format : 2
Unique ID Length : 9
Unique ID : \_SB.FUR3
FWIW, I've checked on one of the AMD server systems we have on the
lab, and the IVHD entries are fairly similar to the ones here, as
neither the PCI Host Bridge, nor the IOMMU are covered by any IVHD
block. That system however doesn't have any IVMD blocks.
> > Relax IVMD parsing: allow IVMD blocks to reference devices not assigned to
> > any
> > IOMMU. It's impossible for Xen to fulfill the requirement in the IVMD
> > block if
> > the device is not behind any IOMMU, but it's no worse than booting without
> > IOMMU support, and thus not parsing ACPI IVRS in the first place.
> >
> > Reported-by: Willi Junga <xenproject@xxxxxx>
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > ---
> > xen/drivers/passthrough/amd/iommu_acpi.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/xen/drivers/passthrough/amd/iommu_acpi.c
> > b/xen/drivers/passthrough/amd/iommu_acpi.c
> > index 3f5508eba049..c416120326c9 100644
> > --- a/xen/drivers/passthrough/amd/iommu_acpi.c
> > +++ b/xen/drivers/passthrough/amd/iommu_acpi.c
> > @@ -248,8 +248,9 @@ static int __init register_range_for_device(
> > iommu = find_iommu_for_device(seg, bdf);
> > if ( !iommu )
> > {
> > - AMD_IOMMU_ERROR("IVMD: no IOMMU for Dev_Id %#x\n", bdf);
> > - return -ENODEV;
> > + AMD_IOMMU_WARN("IVMD: no IOMMU for device %pp - ignoring
> > constrain\n",
>
> I'm not a native speaker, but "constrain" to me can only be a verb (with
> "constraint" being the noun). IOW as worded I'm afraid I can't make sense
> of the message.
Indeed, sorry for the typo.
> > + &PCI_SBDF(seg, bdf));
> > + return 0;
> > }
> > req = ivrs_mappings[bdf].dte_requestor_id;
> >
>
> Down from here in parse_ivmd_device_iommu() is somewhat similar code.
> Wouldn't that need adjusting similarly then? Or else shouldn't the
> adjustment above be accompanied by a comment clarifying that the
> behavior is just because of observations on certain hardware?
Hm, I think that one is bogus and should be removed, according to my
copy of the AMD-Vi spec (48882—Rev 3.08-PUB—Oct 2023), the IVMD type
can only be:
20h=all peripherals
21h=specified peripheral
22h=peripheral range
So type 23h (ACPI_IVRS_TYPE_MEMORY_IOMMU) is not a valid type for the
IVMD blocks.
Thanks, Roger.
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