On Wed, 2 Nov 2022 18:42:21 -0500 Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > [+cc Alex, Myron] > > On Mon, Oct 31, 2022 at 02:45:01PM -0700, francisco.munoz.ruiz@xxxxxxxxxxxxxxx wrote: > > From: Francisco Munoz <francisco.munoz.ruiz@xxxxxxxxxxxxxxx> > > > > The reset was never applied in the current implementation because Intel > > Bridges owned by VMD are parentless. Internally, pci_reset_bus applies > > a reset to the parent of the pci device supplied as argument, but in this > > case it failed because there wasn't a parent. > > > > In more detail, this change allows the VMD driver to enumerate NVMe devices > > in pass-through configurations when host reboots are performed. Commit id > > “6aab5622296b990024ee67dd7efa7d143e7558d0” attempted to fix this, but > > later we discovered that the code inside pci_reset_bus wasn’t triggering > > secondary bus resets. Therefore, we updated the parameters passed to > > it, and now NVMe SSDs attached to VMD bridges are properly enumerated in > > VT-d pass-through scenarios. > > Did you mean "guest reboots" above? If the *host* reboots, I assume > everybody (host and guests) starts over, so a reset wouldn't really > apply. > > Is the scenario that the VMD device is passed through to a guest, and > the guest OS is running vmd_probe() and vmd_enable_domain()? > > I thought VFIO already had something to reset devices between guests. > But maybe this is different because from the point of view of VFIO, > the pass-through happens only once, and during that single session, > the guest OS reboots several times, so you want vmd_probe() to reset > the downstream devices? > > Should this have a Fixes: tag for 6aab5622296b? > > s/pci/PCI/ above in English text. > > Also add "()" after function names. > > Use the typical 12-char SHA1 + subject citation, e.g., 6aab5622296b > ("PCI: vmd: Clean up domain before enumeration"). > > > Signed-off-by: Francisco Munoz <francisco.munoz.ruiz@xxxxxxxxxxxxxxx> > > Reviewed-by: Nirmal Patel <nirmal.patel@xxxxxxxxxxxxxxx> > > --- > > drivers/pci/controller/vmd.c | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c > > index e06e9f4fc50f..34d6ba675440 100644 > > --- a/drivers/pci/controller/vmd.c > > +++ b/drivers/pci/controller/vmd.c > > @@ -859,8 +859,16 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features) > > > > pci_scan_child_bus(vmd->bus); > > vmd_domain_reset(vmd); > > - list_for_each_entry(child, &vmd->bus->children, node) > > - pci_reset_bus(child->self); > > + > > + list_for_each_entry(child, &vmd->bus->children, node) { > > + if (!list_empty(&child->devices)) { > > + pci_reset_bus(list_first_entry(&child->devices, > > + struct pci_dev, > > + bus_list)); Do you want to test the return value here to avoid another case of not actually doing what we expect it to do? WARN_ON perhaps? Thanks, Alex > > + break; > > + } > > + } > > + > > pci_assign_unassigned_bus_resources(vmd->bus); > > > > /* > > -- > > 2.25.1 > > > > Hi Bjorn, > > > > I updated the commit message with more details. Hopefully, this will > > clarify its purpose. > > > > Thanks, > > Francisco. >