Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932339AbaKSUjl (ORCPT ); Wed, 19 Nov 2014 15:39:41 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:51896 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756316AbaKSUjk (ORCPT ); Wed, 19 Nov 2014 15:39:40 -0500 Date: Wed, 19 Nov 2014 15:39:14 -0500 From: Konrad Rzeszutek Wilk To: Juergen Gross Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, david.vrabel@citrix.com, boris.ostrovsky@oracle.com, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com Subject: Re: [PATCH V3 8/8] xen: Speed up set_phys_to_machine() by using read-only mappings Message-ID: <20141119203914.GC18495@laptop.dumpdata.com> References: <1415684626-18590-1-git-send-email-jgross@suse.com> <1415684626-18590-9-git-send-email-jgross@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415684626-18590-9-git-send-email-jgross@suse.com> User-Agent: Mutt/1.5.23 (2014-03-12) 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 On Tue, Nov 11, 2014 at 06:43:46AM +0100, Juergen Gross wrote: > Instead of checking at each call of set_phys_to_machine() whether a > new p2m page has to be allocated due to writing an entry in a large > invalid or identity area, just map those areas read only and react > to a page fault on write by allocating the new page. > > This change will make the common path with no allocation much > faster as it only requires a single write of the new mfn instead > of walking the address translation tables and checking for the > special cases. > > Suggested-by: David Vrabel > Signed-off-by: Juergen Gross Clever! Reviewed-by: Konrad Rzeszutek Wilk > --- > arch/x86/xen/p2m.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c > index 7df446d..58cf04c 100644 > --- a/arch/x86/xen/p2m.c > +++ b/arch/x86/xen/p2m.c > @@ -70,6 +70,7 @@ > > #include > #include > +#include > > #include > #include > @@ -313,9 +314,9 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m) > paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT); > for (i = 0; i < PTRS_PER_PTE; i++) { > set_pte(p2m_missing_pte + i, > - pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL)); > + pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO)); > set_pte(p2m_identity_pte + i, > - pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL)); > + pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO)); > } > > for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) { > @@ -362,7 +363,7 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m) > p2m_missing : p2m_identity; > ptep = populate_extra_pte((unsigned long)(p2m + pfn)); > set_pte(ptep, > - pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL)); > + pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO)); > continue; > } > > @@ -621,6 +622,9 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) > return true; > } > > + if (likely(!__put_user(mfn, xen_p2m_addr + pfn))) > + return true; > + > ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level); > BUG_ON(!ptep || level != PG_LEVEL_4K); > > @@ -630,9 +634,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) > if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity))) > return mfn == IDENTITY_FRAME(pfn); > > - xen_p2m_addr[pfn] = mfn; > - > - return true; > + return false; > } > > bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) > -- > 2.1.2 > -- 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/