David Vrabel <dvra...@cantab.net> wrote: >On 25/10/13 16:03, Konrad Rzeszutek Wilk wrote: >> >> 2). Assume that INVALID_P2M_ENTRY is considered 1-1. That would >require >> auditing of the code and also making sure that any >xen_privcmd_mmap >> calls use the m2p_add_override. > >I'm not sure I understand the concern about the privcmd driver's >foreign >mapping ioctls (MMAPBATCH_V2 and friends) as these all deal with MFNs >directly and don't use the p2m. > >> However there are some >> valid cases in which we need to check for INVALID_P2M_ENTRY - >> balloon driver - that might be relaxed. > >Yes. And this behaviour will be retained. I think we only need to do > >the INVALID_P2M_ENTRY => 1:1 when constructing PTEs so all other >callers >will see INVALID_P2M_ENTRY as before.
You are suggesting not touching the p2m code and instead change the the xen-make-pte to assume that INVALID and IDENTITY should have the same behaviour. Interesting. > > >> However again the P2M code >> and the ABI it places are not for the faint of the heart. > >I have no fear. :-) > >If the above suggestion does work out it will reduce the amount of p2m >code /and/ remove a Xen-specific PTE bit. So I think it is worth >pursuing. > >In the meantime, the following minimal patch is a likely workaround. > >David > >8<------------------------------- >x86/mm: set _PAGE_IOMAP in io_remap_pfn_range(). > >Signed-off-by: David Vrabel <david.vra...@citrix.com> >--- > arch/x86/include/asm/pgtable.h | 3 +++ > 1 file changed, 3 insertions(+) > >diff --git a/arch/x86/include/asm/pgtable.h >b/arch/x86/include/asm/pgtable.h >index 3d19994..d59b22a 100644 >--- a/arch/x86/include/asm/pgtable.h >+++ b/arch/x86/include/asm/pgtable.h >@@ -868,6 +868,9 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t >pte) > return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY); > } > >+#define io_remap_pfn_range(vma, addr, pfn, size, prot) \ >+ remap_pfn_range(vma, addr, pfn, size, (prot) | _PAGE_IOMAP) >+ > #include <asm-generic/pgtable.h> > #endif /* __ASSEMBLY__ */ You are welcome to suggest it to hpa. Last time a similar patch was proposed he was not too thrilled about it. Looking forward to your p2m code surgery! -- 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/
