From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 01/10] KVM: SVM: Don't use kmap_atomic in nested_svm_map Date: Thu, 18 Feb 2010 15:40:56 +0200 Message-ID: <4B7D4368.6020903@redhat.com> References: <1266493115-28386-1-git-send-email-joerg.roedel@amd.com> <1266493115-28386-2-git-send-email-joerg.roedel@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org To: Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:40061 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754324Ab0BRNlI (ORCPT ); Thu, 18 Feb 2010 08:41:08 -0500 In-Reply-To: <1266493115-28386-2-git-send-email-joerg.roedel@amd.com> Sender: kvm-owner@vger.kernel.org List-ID: On 02/18/2010 01:38 PM, Joerg Roedel wrote: > Use of kmap_atomic disables preemption but if we run in > shadow-shadow mode the vmrun emulation executes kvm_set_cr3 > which might sleep or fault. So use kmap instead for > nested_svm_map. > > > > -static void nested_svm_unmap(void *addr, enum km_type idx) > +static void nested_svm_unmap(void *addr) > { > struct page *page; > > @@ -1443,7 +1443,7 @@ static void nested_svm_unmap(void *addr, enum km_type idx) > > page = kmap_atomic_to_page(addr); > > - kunmap_atomic(addr, idx); > + kunmap(addr); > kvm_release_page_dirty(page); > } > kunmap() takes a struct page *, not the virtual address (a consistent source of bugs). kmap() is generally an unloved interface, it is slow and possibly deadlock prone, but it's better than sleeping in atomic context. If you can hack your way around it, that is preferred. -- error compiling committee.c: too many arguments to function