From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: [PATCH 2/2] KVM: Use pci_store/load_saved_state() around VM device usage Date: Fri, 15 Apr 2011 14:13:50 -0600 Message-ID: <1302898430.3110.31.camel@x201> References: <20110415194220.2838.10750.stgit@s20.home> <20110415195439.2838.58928.stgit@s20.home> <4DA8A493.8000509@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: linux-pci@vger.kernel.org, kvm@vger.kernel.org, avi@redhat.com, jbarnes@virtuousgeek.org To: Jan Kiszka Return-path: In-Reply-To: <4DA8A493.8000509@web.de> Sender: linux-pci-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, 2011-04-15 at 22:03 +0200, Jan Kiszka wrote: > On 2011-04-15 21:54, Alex Williamson wrote: > > Store the device saved state so that we can reload the device back > > to the original state when it's unassigned. This has the benefit > > that the state survives across pci_reset_function() calls via > > the PCI sysfs reset interface while the VM is using the device. > > > > Signed-off-by: Alex Williamson > > --- > > > > include/linux/kvm_host.h | 1 + > > virt/kvm/assigned-dev.c | 8 +++++--- > > 2 files changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index ab42855..d8a1d18 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -513,6 +513,7 @@ struct kvm_assigned_dev_kernel { > > struct kvm *kvm; > > spinlock_t intx_lock; > > char irq_name[32]; > > + void *pci_saved_state; > > }; > > > > struct kvm_irq_mask_notifier { > > diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c > > index ae72ae6..66c6ccd 100644 > > --- a/virt/kvm/assigned-dev.c > > +++ b/virt/kvm/assigned-dev.c > > @@ -197,7 +197,9 @@ static void kvm_free_assigned_device(struct kvm *kvm, > > { > > kvm_free_assigned_irq(kvm, assigned_dev); > > > > - __pci_reset_function(assigned_dev->dev); > > + pci_reset_function(assigned_dev->dev); > > + pci_load_and_free_saved_state(assigned_dev->dev, > > + &assigned_dev->pci_saved_state); > > pci_restore_state(assigned_dev->dev); > > > > pci_release_regions(assigned_dev->dev); > > @@ -516,7 +518,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm, > > > > pci_reset_function(dev); > > pci_save_state(dev); > > - > > + match->pci_saved_state = pci_store_saved_state(dev); > > match->assigned_dev_id = assigned_dev->assigned_dev_id; > > match->host_segnr = assigned_dev->segnr; > > match->host_busnr = assigned_dev->busnr; > > @@ -546,7 +548,7 @@ out: > > mutex_unlock(&kvm->lock); > > return r; > > out_list_del: > > - pci_restore_state(dev); > > + pci_load_and_free_saved_state(dev, &match->pci_saved_state); > > Don't you need to keep the balance, ie. load_and_free, then restore? I don't see that pci_save_state() does anything more than buffer the hardware device state into save areas in struct pci_dev. So by not doing a restore, we are leaving that valid, but I don't really see how that hurts anything. The only reason we even really need to call pci_load_and_free_saved_state() here is to free the buffer Thanks, Alex > > list_del(&match->list); > > pci_release_regions(dev); > > out_disable: > > > > Thanks for addressing the issue! > > Jan >