From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Date: Wed, 06 Jun 2012 12:28:59 +0000 Subject: Re: [PATCH] KVM: PPC: Book3S HV: Drop locks around call to kvmppc_pin_guest_page Message-Id: <4FCF4D0B.9040309@redhat.com> List-Id: References: <20120601102024.GB11714@pale.ozlabs.ibm.com> In-Reply-To: <20120601102024.GB11714@pale.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Paul Mackerras Cc: Alexander Graf , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org On 06/01/2012 01:20 PM, Paul Mackerras wrote: > At the moment we call kvmppc_pin_guest_page() in kvmppc_update_vpa() > with two spinlocks held: the vcore lock and the vcpu->vpa_update_lock. > This is not good, since kvmppc_pin_guest_page() calls down_read() and > get_user_pages_fast(), both of which can sleep. This bug was introduced > in 2e25aa5f ("KVM: PPC: Book3S HV: Make virtual processor area > registration more robust"). > > This arranges to drop those spinlocks before calling > kvmppc_pin_guest_page() and re-take them afterwards. Dropping the > vcore lock in kvmppc_run_core() means we have to set the vcore_state > field to VCORE_RUNNING before we drop the lock, so that other vcpus > won't try to run this vcore. > > Signed-off-by: Paul Mackerras > --- > Since this bug is in Linus' tree, and it can cause a scheduling while > atomic bug message, can we send this to Linus for inclusion in 3.5, > after review of course? > Sure, Alex? -- error compiling committee.c: too many arguments to function