[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] new hypercall implementation question
> On 07/23/09 07:31, Dan Magenheimer wrote: > > Is it safe to pass three guest virtual addresses via a hypercall > > to Xen and expect Xen to safely copy data (two scalars and one > > array of pagesize-bytes... not necessarily aligned on a page > > boundary) back to the guest, or do I need to do something fancy > > to avoid weird corner cases, e.g. to ensure restartabililty > > in case of guest page fault? > > > > This is a privileged-only hypercall used only as part of > > save/restore/live-migrate (for tmem) if that is relevant. > > > > For x86 its OK to pass kernel vaddrs to Xen and have it interpret them > with the current pagetable. There should be no pagefaults, or rather, > the hypercall will fail with EFAULT. > > I think ia64 has problems with anything other than physical addresses > being passed, and has to do all that handle stuff to convert. Thanks for the reply. After sending, I remembered that the "proper" way to do this in Xen tools is to bracket the hypercall with lock_pages/unlock_pages for any vaddr passed to the hypercall. I hope that's not too horribly expensive. Thanks, Dan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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