Re: [Xen-ia64-devel] [PATCH] [RFC] [TAKE3] P2M/VP (incomplete) patches

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Hi.

On Fri, Mar 24, 2006 at 11:11:38PM +0800, Tian, Kevin wrote:
>       A quality writing and good work by far. Due to memory model as the 
> most critical/basic component, your work is actually extended to cover 
> many areas as the issues posted below. :-) Maybe you have to make a 
> priority list, and see whether some core components can be split into 
> self-contained parts with major cleanup efforts paid for them first.

Here is the categorized and prioritized list of issues.
These priority is for short/middle term(1-3 months).
Although others might think differently with these priority,
I hope this list helps.


* Issues directly related to the P2M/VP patches.
The following issues are directly related the P2M/VP patches.
Perhaps performance tuning/benchmarking can be done in parallel.

- High  discussion on grant table API clean up/performance tuning
- High  grant table API clean up
        This must be after the discussion.
- High  ballon driver
        XENMEM_populate_physmap, XENMEM_decrease_reservation,
        XENMEM_increase_reservation
- High  SMP
        Currently nosmp option to xen/IA64 is needed.
        This will be addressed after grant table API clean up.
        This must be before grant table performance tuning
- High  performance tuning related to grant table.
        - micro benchmark?
          Is there already suitable benchmarks or should it be developed?
- High  performance tuning unrelated to grant table.
- Med   grant table mapped page reference count and domain destruction
        This should be after grant table API clean up and performance tuning.
        If a domain is destroyed when it maps a foreign domain's page
        via grant table, its page reference count will be leaked.
        Page freeing code is needed.
- Low   xen_start_info->{console_mfn, store_mfn}
        These are defined as machine frame number. However on Xen/IA64 with
        P2M/VP model, these should be pseudo physical frame number.
        So they should be gmfn instead of mfn.
- Low   IOCTL_PRIVCMD_MMAP, IOCTL_PRIVCMD_MMAPBATCH
        re-implement xen/IA64 implementation using PageForeign() and
        its families.
- Low   blktap


* Issues which can be worked independently of P2M/VP model.
The following issues are unrelated the P2M/VP patches or
depends on the stabilized part of P2M/VP patches
so that they can be worked independently of the P2M/VP model patches.

** Platform support
- Low   HP ZX1
  High for HP(?)
        Some modification is necessary for
        linux/arch/ia64/hp/common/sba_iommu.c.
- Low   SGI Altix
  High for SGI(?)
        There are many custom drivers under linux/arch/ia64/sn directory.
        They also need modifications.
- Low   ski simulator
        simscsi, simeth are broken. dom0 can't boot.

** Testing
- Low   AGP
        AGP should work, but I haven't tested it.
- Low   virtualized driver
        Only vbd and vnif are tested.
        Other virtual devices except balloon and blktap should work.
- Low   transparent para-virtualization
        Some of xen/IA64 developers value transparent para-virtualization.
        "if (running_on_xen) { }" is be used, but it isn't tested.
        Or is it worthwhile to define a kind of switch which is determined at
        boot up time ?
- Low   Stability test, benchmark
        This might be too early to begin.

** Bug fixes and misc
- High  copy_to_guest(), copy_from_guest()
        They are broken.
        Their copy may success or may result in EFAULT depending on tlb cache
        state.
        Fortunately xen/PPC port already solved similar problems.
        Discussion is needed.
- Low   panic_domain()
        This function is called when a domain behaves a way xen can't handle
        well.
        A domain should be stopped, but xen should continue to run.
        But the current implementation results in BUG() in xen or drops to
        debugger so that xen itself stops.
- Low   SUBARCH
- Low   dltb miss handler optimization
- Low   itlb miss handler fix
        fix dom0 startup environment to remove alt itlb miss which occurs
        at dom0 boot time.


* My plan
high priority
- discussion on grant table API clean up / performance tuning
- getting balloon driver to work

- grant table API clean up
- SMP
- performance tuning related to grant table

- performance tuning unrelated to grant table.
- stability/testing/benchmark
- merge effort
low priority


-- 
yamahata

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