From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH] KVM: MMU: fix huge page adapted on non-PAE host Date: Mon, 28 May 2012 19:39:26 +0800 Message-ID: <4FC363EE.6060204@linux.vnet.ibm.com> References: <4FC316E3.6080607@linux.vnet.ibm.com> <4FC35A15.6080000@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Avi Kivity Return-path: Received: from e28smtp06.in.ibm.com ([122.248.162.6]:42004 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183Ab2E1NYK (ORCPT ); Mon, 28 May 2012 09:24:10 -0400 Received: from /spool/local by e28smtp06.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 28 May 2012 18:49:10 +0530 In-Reply-To: <4FC35A15.6080000@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 05/28/2012 06:57 PM, Avi Kivity wrote: > On 05/28/2012 09:10 AM, Xiao Guangrong wrote: >> The huge page size is 4M on non-PAE host, but 2M page size is used in >> transparent_hugepage_adjust(), so the page we get after adjust the >> mapping level is not the head page, the BUG_ON() will be triggered >> >> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >> index 72102e0..be3cea4 100644 >> --- a/arch/x86/kvm/mmu.c >> +++ b/arch/x86/kvm/mmu.c >> @@ -2595,8 +2595,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu, >> *gfnp = gfn; >> kvm_release_pfn_clean(pfn); >> pfn &= ~mask; >> - if (!get_page_unless_zero(pfn_to_page(pfn))) >> - BUG(); >> + kvm_get_pfn(pfn); >> *pfnp = pfn; >> } >> } > > Shouldn't we adjust mask instead? > Adjusting mask to map the whole 4M huge page to KVM guest? But it seams 4M page size is not supported on VMX/SVM.