From 706cc9d2a4cb9b03217e15b0bb3d117f4d5109ee Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Wed, 2 Feb 2011 18:32:59 +0000 Subject: [PATCH] xen/m2p: Check whether the MFN has IDENTITY_FRAME bit set.. If there is no proper PFN value in the M2P for the MFN (so we get 0xFFFFF.. or 0x55555, or 0x0), we should consult the M2P override to see if there is an entry for this. [Note: we also consult the M2P override if the MFN is past our machine_to_phys size]. We consult the P2M with the PFN. In case the returned MFN is one of the special values: 0xFFF.., 0x5555 (which signify that the MFN can be either "missing" or it belongs to DOMID_IO) or the p2m(m2p(mfn)) != mfn, we check the M2P override. If we fail the M2P override check, we reset the PFN value to INVALID_P2M_ENTRY. Next we try to find the MFN in the P2M using the MFN value (not the PFN value) and if found, we know that this MFN is an identity value and return it as so. Otherwise we have exhausted all the posibilities and we return the PFN, which at this stage can either be a real PFN value found in the machine_to_phys.. array, or INVALID_P2M_ENTRY value. [v1: Added Review-by tag] Reviewed-by: Ian Campbell Signed-off-by: Konrad Rzeszutek Wilk --- arch/x86/include/asm/xen/page.h | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h index 19570706049..c61934fbf22 100644 --- a/arch/x86/include/asm/xen/page.h +++ b/arch/x86/include/asm/xen/page.h @@ -81,6 +81,7 @@ static inline int phys_to_machine_mapping_valid(unsigned long pfn) static inline unsigned long mfn_to_pfn(unsigned long mfn) { unsigned long pfn; + int ret = 0; if (xen_feature(XENFEAT_auto_translated_physmap)) return mfn; @@ -95,15 +96,29 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn) * In such cases it doesn't matter what we return (we return garbage), * but we must handle the fault without crashing! */ - __get_user(pfn, &machine_to_phys_mapping[mfn]); + ret = __get_user(pfn, &machine_to_phys_mapping[mfn]); try_override: - /* - * If this appears to be a foreign mfn (because the pfn - * doesn't map back to the mfn), then check the local override - * table to see if there's a better pfn to use. + /* ret might be < 0 if there are no entries in the m2p for mfn */ + if (ret < 0) + pfn = ~0; + else if (get_phys_to_machine(pfn) != mfn) + /* + * If this appears to be a foreign mfn (because the pfn + * doesn't map back to the mfn), then check the local override + * table to see if there's a better pfn to use. + * + * m2p_find_override_pfn returns ~0 if it doesn't find anything. + */ + pfn = m2p_find_override_pfn(mfn, ~0); + + /* + * pfn is ~0 if there are no entries in the m2p for mfn or if the + * entry doesn't map back to the mfn and m2p_override doesn't have a + * valid entry for it. */ - if (get_phys_to_machine(pfn) != mfn) - pfn = m2p_find_override_pfn(mfn, pfn); + if (pfn == ~0 && + get_phys_to_machine(mfn) == IDENTITY_FRAME(mfn)) + pfn = mfn; return pfn; } -- 2.41.0