On Wed, 22 Nov 2017 12:46:45 +0200 Marcel Apfelbaum <mar...@redhat.com> wrote:
> Hi Ladi, > > On 20/11/2017 16:22, Ladi Prosek wrote: > > msix_mask_all() is supposed to invoke the release vector notifier if the > > state of the > > respective vector changed from unmasked or masked. > > You mean from unmasked "to" masked right? > > The way it's currently called from > > msix_reset(), though, may result in calling the release notifier even if > > the vector > > is already masked. > > > > 1) msix_reset() clears out the msix_cap field and the msix_table. > > 2) msix_mask_all() runs with was_masked=false for all vectors because of > > 1), which > > results in calling the release notifier on all vectors. > > 3) if msix_reset() is subsequently called again, it goes through the same > > steps and > > calls the release notifier on all vectors again. > > > > As far as I can see in the code you are right.(very reset will trigger the > release notifiers > again) > > > This commit moves msix_mask_all() up so it runs before the device state is > > lost. > > OK > > > And > > it adds a call to msix_update_function_masked() so that the device > > remembers that > > MSI-X is masked. > > > > msix_update_function_masked checks the msix is enabled or masked-off. > You are building on the fact the msix will not be enabled to set > "msix_function_masked" to "true", right? > (I just want to be sure I understand the patch) > > > This is likely a low impact issue, found while debugging an already broken > > device. It > > is however easy to fix and the expectation that the use and release > > notifier invocations > > are always balanced is very natural. > > > > I would leave it (maybe) out of 2.11 because it may expose other bugs > and we are after rc2 already. > > Adding Alex Williamson to see it does not affect device assignment, > other than that the patch looks OK to me. I flip flopped around here because vfio_msix_vector_release() doesn't care if it gets called more than once for the same vector, but then I looked at the ordering of vfio_pci_reset() vs msix_reset(). vfio will never leave vfio_pci_reset() with MSI-X enabled, we unset our notifiers , release and unuse any in-use vectors, and leave with only INTx enabled (if supported). So I don't think the patch below has any effect whatsoever for vfio, and probably shouldn't for most devices as resetting back to a state of MSI-X disabled ought to be standard procedure... but maybe other devices rely on msix_reset() for this. Thanks, Alex > > Signed-off-by: Ladi Prosek <lpro...@redhat.com> > > --- > > hw/pci/msix.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/hw/pci/msix.c b/hw/pci/msix.c > > index c944c02135..34656de9b0 100644 > > --- a/hw/pci/msix.c > > +++ b/hw/pci/msix.c > > @@ -500,11 +500,12 @@ void msix_reset(PCIDevice *dev) > > return; > > } > > msix_clear_all_vectors(dev); > > + msix_mask_all(dev, dev->msix_entries_nr); > > dev->config[dev->msix_cap + MSIX_CONTROL_OFFSET] &= > > ~dev->wmask[dev->msix_cap + MSIX_CONTROL_OFFSET]; > > memset(dev->msix_table, 0, dev->msix_entries_nr * > > PCI_MSIX_ENTRY_SIZE); > > memset(dev->msix_pba, 0, QEMU_ALIGN_UP(dev->msix_entries_nr, 64) / 8); > > - msix_mask_all(dev, dev->msix_entries_nr); > > + msix_update_function_masked(dev); > > } > > > > /* PCI spec suggests that devices make it possible for software to > > configure > > >
