[intel-platform-dev] IO Virtual Address management questions.

[Baolu Lu]

Hi Mark,

In addition to these questions, can I add another one?

We need function interfaces to allocate/free the iommu pages. The page
size is 4k. Can the following steps work? If so, what are the
functions in each step?

1. allocate a physical page
2. lock this page
3. map this page to virtual address

Can you give me some reference code in the kernel source tree?

Thanks

On Nov 14, 2007 8:44 AM, Raj, Ashok <ashok.raj at intel.com> wrote:
> Hi Mark
>
> Here goes the second question about iova management. Basically iam
> looking for 2 things
>
> 1. A way to carve out ranges that cannot be allocated.
> 2. A way to clone the iova areana for each new domain I allocate.
>
> Seems like I can use the same for other domain allocation code, looks
> like I can use it generically even as a bitvec allocator. Say I have 256
> domains, I could just use this with granularity of 1, just like how the
> dtrace code is using it?
>
> More details below.
>
> IO Virtual Address space management.
> ------------------------------------
> 1. We need a method to allocate io virtual address (IOVA). Solaris
> already has
>    support for this via vmem_create(), vmem_alloc() and vmem_free().
>
>    We need to create holes in the address space for the following items.
>
>    - Remove APIC address range 0xfee00000 - 0xfeefffff
>    - Remove certain 1-1 ranges, such as RMRR's from an address map
>    - Remove any mem ranges that exist under p2p side to avoid peer to
> peer
>    pci side effects. It would be simple to just remove them from the
> address
>    range.
>
>    What is the best way to punch holes in the vmem arena. I see two ways
>    but not sure if there is a better way.
>
>    If there is a new api like vmem_del(vmem_t *, void *addr, size_t
> size)
>
>    And is there a way to clone the areana created? we would need to do
> this
>    each time we create a iova for each domain to manage. It might be
> easy if
>    i had an iova areana with holes, and just clone them for each new
> domain
>    i create.
>
>    it would be great if vmem could do the splicing. Without something
> like this
>
>    - We could add and create the areana leaving holes with multiple
> vmem_add()
>    calls.
>
>
>    - Just create a large address space, and use vmem_xalloc() to
> allocate and
>    remove these holes. Performance is not a problem since this is
> startup time
>    not speed path.
>
>    say
>
>         since we will only map at page granurality its enough if we
>         account just page numbers.
>
>         iova_area = vmem_create(name, 1, BTOP(UINT64_MAX), 1, NULL,
> NULL, NULL,
>                     0, VM_SLEEP | VMC_IDENTIFIER);
>
>         but to cut out the un-allocatable holes say for e.g
>
>         vmem_xalloc(iova_area, 0xff, 1, 0, 0xfee00, 0xfeeff, VM_SLEEP);
>
> Cheers,
> ashok raj
> - Open Source Technology Center
>
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