Re: [Xen-devel] [PATCH v3 2/7] docs: Improve documentation and parsing for iommu=

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.01.19 at 10:00, <andrew.cooper3@xxxxxxxxxx> wrote:
>[...]
> +The functionality in an IOMMU commonly falls into two orthogonal categories:
>  
> -> Default: `false`
> -
> ->> Don't continue booting unless IOMMU support is found and can be 
> initialized
> ->> successfully.
> +1.  DMA remapping which uses a pagetable-like hierarchical structure and maps
> +    I/O Virtual Addresses (DFNs - Device Frame Numbers in Xen's terminology)
> +    to System Physical Addresses (MFNs - Machine Frame Numbers in Xen's
> +    terminology).
>  
> -> `intremap`
> +2.  Interrupt Remapping, which controls incoming Message Signalled Interrupt
> +    requests, including their routing to specific CPUs.
>  
> -> Default: `true`
> +IOMMU functionality can be used either to provide a translation which the

Instead of the "either" here, would it be better to use ...

> +hardware device driver isn't aware of (e.g. PCI Passthrough and a native
> +driver inside the guest) or to enforce fine-grained control over the memory

... "and/or" here?

> +and interrupts which a device is attempting to access.
>[...]
> +The following options are specific to Intel VT-d hardware:
>  
> -> Default: `false`
> +*   The `snoop` boolean controls the Snoop Control sub-feature, and is
> +    active by default on compatible hardware.
>  
> ->> Causes DRHD entries without any PCI discoverable devices under them to be
> ->> ignored (normally IOMMU setup fails if any of the devices listed by a DRHD
> ->> entry aren't PCI discoverable).
> +    An incomming DMA request may specify _Snooped_ (query the CPU caches

incoming ?

Apart from these
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



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