On 07/11/14 14:11, Juergen Gross wrote: > On 11/07/2014 02:54 PM, David Vrabel wrote: >> On 06/11/14 05:47, Juergen Gross wrote: >> [...] >>> @@ -526,23 +411,83 @@ unsigned long get_phys_to_machine(unsigned long >>> pfn) >>> return IDENTITY_FRAME(pfn); >>> } >>> >>> - topidx = p2m_top_index(pfn); >>> - mididx = p2m_mid_index(pfn); >>> - idx = p2m_index(pfn); >>> + ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level); >>> + BUG_ON(!ptep || level != PG_LEVEL_4K); >>> >>> /* >>> * The INVALID_P2M_ENTRY is filled in both p2m_*identity >>> * and in p2m_*missing, so returning the INVALID_P2M_ENTRY >>> * would be wrong. >>> */ >>> - if (p2m_top[topidx][mididx] == p2m_identity) >>> + if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity))) >>> return IDENTITY_FRAME(pfn); >>> >>> - return p2m_top[topidx][mididx][idx]; >>> + return xen_p2m_addr[pfn]; >> >> You should test xen_p2m_addr[pfn] == INVALID_P2M_ENTRY before checking >> if it's an identity entry. This should skip the more expensive >> lookup_address() in the common case. > > I do. The check is in __pfn_to_mfn(). get_phys_to_machine() is called in > this case only.
So you do. I missed that. >>> bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) >> >> I think you should map p2m_missing and p2m_identity as read-only and do >> the new page allocation on a write fault. >> >> set_phys_to_machine() is used every grant map and unmap and in the >> common case (already allocated array page) it must be a fast and simple: >> >> xen_p2m_addr[pfn] = mfn; > > Nice idea. I'll try it. You probably want to try this with a custom exception fixup (or abuse put_user()). David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
