Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752354Ab3JYXje (ORCPT ); Fri, 25 Oct 2013 19:39:34 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:20556 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753272Ab3JYXjd convert rfc822-to-8bit (ORCPT ); Fri, 25 Oct 2013 19:39:33 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <526AF79A.3050002@cantab.net> References: <1382713401-4882-1-git-send-email-konrad.wilk@oracle.com> <526AF79A.3050002@cantab.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset=UTF-8 Subject: Re: [Xen-devel] [PATCH v1] Set 1-1 P2M for PCI BARs and MCFG regions - if needed. From: Konrad Rzeszutek Wilk Date: Fri, 25 Oct 2013 19:39:05 -0400 To: David Vrabel CC: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, Santosh.Jodh@citrix.com, JBeulich@suse.com, boris.ostrovsky@oracle.com, david.vrabel@citrix.com, mukesh.rathor@oracle.com, xhejtman@ics.muni.cz, yuval.shaia@oracle.com Message-ID: X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2493 Lines: 74 David Vrabel 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 >--- > 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 > #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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/