From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: VMX: Fix repeatly allocate of apic access page Date: Tue, 06 Nov 2007 11:23:00 +0200 Message-ID: <47303274.5070405@qumranet.com> References: <200711061100.35700.sheng.yang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Sheng Yang Return-path: In-Reply-To: <200711061100.35700.sheng.yang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Sheng Yang wrote: > From 05164d73994a88ae130a086b592cd127c15a617f Mon Sep 17 00:00:00 2001 > From: Sheng Yang > Date: Tue, 6 Nov 2007 11:37:44 +0800 > Subject: [PATCH] KVM: VMX: Fix repeatly allocate of apic access page > > For SMP guest, alloc_apic_access_page() would be called more than once. > So only the last one works, causing SMP guest can't benifit from FlexPriority. > > This patch fixed this issue. > > Signed-off-by: Sheng Yang > --- > drivers/kvm/vmx.c | 14 ++++++++++---- > 1 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c > index 42e7fad..6670e2b 100644 > --- a/drivers/kvm/vmx.c > +++ b/drivers/kvm/vmx.c > @@ -1463,18 +1463,24 @@ static void seg_setup(int seg) > static int alloc_apic_access_page(struct kvm *kvm) > { > struct kvm_userspace_memory_region kvm_userspace_mem; > - int r; > + int r = 0; > > - r = -EFAULT; > + mutex_lock(&kvm->lock); > + if (kvm->apic_access_page) > + goto out; > + mutex_unlock(&kvm->lock); > Still racy. I two threads create a vcpu at the same time, they can both reach this point simultaneously. I suggest having a __kvm_set_memory_region() that does not take kvm->lock, and call that instead, so the whole thing can be done within a single lock. > kvm_userspace_mem.slot = APIC_ACCESS_PAGE_PRIVATE_MEMSLOT; > kvm_userspace_mem.flags = 0; > kvm_userspace_mem.guest_phys_addr = 0xfee00000ULL; > kvm_userspace_mem.memory_size = PAGE_SIZE; > r = kvm_set_memory_region(kvm, &kvm_userspace_mem, 0); > if (r) > - return r; > + goto out; > + mutex_lock(&kvm->lock); > kvm->apic_access_page = gfn_to_page(kvm, 0xfee00); > - return 0; > +out: > + mutex_unlock(&kvm->lock); > + return r; > } > > -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/