Re: [Xen-devel] [PATCH] privcmd: MMAPBATCH: Fix error handling/reporting

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Wed, 2009-05-20 at 15:33 -0400, Jeremy Fitzhardinge wrote:
> Ian Campbell wrote:
> > On error IOCTL_PRIVCMD_MMAPBATCH is expected to set the top nibble of
> > the effected MFN and return 0. Currently it leaves the MFN unmodified
> > and returns the number of failures. Therefore:
> >
> > - reimplement remap_domain_mfn_range() using direct
> >   HYPERVISOR_mmu_update() calls and small batches. The xen_set_domain_pte()
> >   interface does not report errors and since some failures are
> >   expected/normal using the multicall infrastructure is too noisy.
> >   
> The noise is just for debugging; if failure is expected, then maybe we 
> can extend it to be quiet about those cases.

In this specific instance going directly at the mmu_udpate interface is
probably better since the propagation of errors from the multicall
infrastructure is tricky (well, currently non-existent). I don't think
multicalls would buy us anything here anyhow since mmu_update is batched
already.

On Wed, 2009-05-20 at 17:13 -0400, Jeremy Fitzhardinge wrote:
> This breaks compiling xenfs as a module; neither flush_tlb_all or 
> arbitrary_virt_to_machine are exported, I think.

Rather than exporting those I think moving remap_domain_mfn_range() to
core code (with xen_ on the front of the name) and exporting that would
be cleaner. Thoughts?

Ian.



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