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Re: [PATCH 4/8] VT-d: refuse to use IOMMU with reserved CAP.ND value
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 12 Apr 2022 12:35:54 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Paul Durrant <paul@xxxxxxx>
- Delivery-date: Tue, 12 Apr 2022 10:36:06 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 12.04.2022 11:22, Roger Pau Monné wrote:
> On Mon, Apr 11, 2022 at 11:37:28AM +0200, Jan Beulich wrote:
>> The field taking the value 7 (resulting in 18-bit DIDs when using the
>> calculation in cap_ndoms(), when the DID fields are only 16 bits wide)
>> is reserved. Instead of misbehaving in case we would encounter such an
>> IOMMU, refuse to use it.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks.
> I would maybe prefer to get more specific error message rather than
> "IOMMU: unsupported" and a dump of the iommu registers.
Perhaps, but this extends to other properties being checked as well then,
I would say, and hence may want to be the subject of yet another patch.
Jan
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