On Wed, Mar 23, 2022 at 01:31:12PM -0700, Michael Kelley wrote: > PCI pass-thru devices in a Hyper-V VM are represented as a VMBus > device and as a PCI device. The coherence of the VMbus device is > set based on the VMbus node in ACPI, but the PCI device has no > ACPI node and defaults to not hardware coherent. This results > in extra software coherence management overhead on ARM64 when > devices are hardware coherent. > > Fix this by setting up the PCI host bus so that normal > PCI mechanisms will propagate the coherence of the VMbus > device to the PCI device. There's no effect on x86/x64 where > devices are always hardware coherent. > > Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Acked-by: Boqun Feng <boqun.feng@xxxxxxxxx> Regards, Boqun > --- > drivers/pci/controller/pci-hyperv.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c > index ae0bc2f..88b3b56 100644 > --- a/drivers/pci/controller/pci-hyperv.c > +++ b/drivers/pci/controller/pci-hyperv.c > @@ -3404,6 +3404,15 @@ static int hv_pci_probe(struct hv_device *hdev, > hbus->bridge->domain_nr = dom; > #ifdef CONFIG_X86 > hbus->sysdata.domain = dom; > +#elif defined(CONFIG_ARM64) > + /* > + * Set the PCI bus parent to be the corresponding VMbus > + * device. Then the VMbus device will be assigned as the > + * ACPI companion in pcibios_root_bridge_prepare() and > + * pci_dma_configure() will propagate device coherence > + * information to devices created on the bus. > + */ > + hbus->sysdata.parent = hdev->device.parent; > #endif > > hbus->hdev = hdev; > -- > 1.8.3.1 > >
