From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754743AbcEXXHA (ORCPT ); Tue, 24 May 2016 19:07:00 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:36204 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751411AbcEXXG7 (ORCPT ); Tue, 24 May 2016 19:06:59 -0400 Date: Tue, 24 May 2016 23:06:55 +0000 From: Wei Yang To: Wei Yang Cc: joro@8bytes.org, dwmw2@infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iommu/vt-d: reduce extra first level entry in iommu->domains Message-ID: <20160524230655.GA28550@vultr.guest> Reply-To: Wei Yang References: <1463798511-4015-1-git-send-email-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1463798511-4015-1-git-send-email-richard.weiyang@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Joerg Not sure whether you think this calculation is correct. If I missed something for this " + 1" in your formula, I am glad to hear your explanation. So that I could learn something from you :-) Have a good day~ On Sat, May 21, 2016 at 02:41:51AM +0000, Wei Yang wrote: >In commit <8bf478163e69> ("iommu/vt-d: Split up iommu->domains array"), it >it splits iommu->domains in two levels. Each first level contains 256 >entries of second level. In case of the ndomains is exact a multiple of >256, it would have one more extra first level entry for current >implementation. > >This patch refines this calculation to reduce the extra first level entry. > >Signed-off-by: Wei Yang >--- > drivers/iommu/intel-iommu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > >diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c >index e3061d3..2204ca4 100644 >--- a/drivers/iommu/intel-iommu.c >+++ b/drivers/iommu/intel-iommu.c >@@ -1634,7 +1634,7 @@ static int iommu_init_domains(struct intel_iommu *iommu) > return -ENOMEM; > } > >- size = ((ndomains >> 8) + 1) * sizeof(struct dmar_domain **); >+ size = (ALIGN(ndomains, 256) >> 8) * sizeof(struct dmar_domain **); > iommu->domains = kzalloc(size, GFP_KERNEL); > > if (iommu->domains) { >@@ -1699,7 +1699,7 @@ static void disable_dmar_iommu(struct intel_iommu *iommu) > static void free_dmar_iommu(struct intel_iommu *iommu) > { > if ((iommu->domains) && (iommu->domain_ids)) { >- int elems = (cap_ndoms(iommu->cap) >> 8) + 1; >+ int elems = ALIGN(cap_ndoms(iommu->cap), 256) >> 8; > int i; > > for (i = 0; i < elems; i++) >-- >1.7.9.5 -- Wei Yang Help you, Help me