Re: [PATCH v4] PCI: vmd: Clean up domain before enumeration

["Patel, Nirmal" <nirmal.patel@linux.intel.com>]

On 10/25/2021 11:29 AM, Nirmal Patel wrote:
> During VT-d pass-through, the VMD driver occasionally fails to
> enumerate underlying NVMe devices when repetitive reboots are
> performed in the guest OS. The issue can be resolved by resetting
> VMD root ports for proper enumeration and triggering secondary bus
> reset which will also propagate reset through downstream bridges.
>
> Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
> Reviewed-by: Jon Derrick <jonathan.derrick@linux.dev>
> ---
> v3->v4: Using pci_reset_bus function for secondary bus reset instead of
>         manually triggering secondary bus reset, addressing review
>         comments of v3.
> v2->v3: Combining two functions into one, Remove redundant definations
>         and Formatting fixes
>
>  drivers/pci/controller/vmd.c | 37 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index a5987e52700e..79f8b86ee45b 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -498,6 +498,40 @@ static inline void vmd_acpi_begin(void) { }
>  static inline void vmd_acpi_end(void) { }
>  #endif /* CONFIG_ACPI */
>  
> +static void vmd_domain_reset(struct vmd_dev *vmd)
> +{
> +	u16 bus, max_buses = resource_size(&vmd->resources[0]);
> +	u8 dev, functions, fn, hdr_type;
> +	char __iomem *base;
> +
> +	for (bus = 0; bus < max_buses; bus++) {
> +		for (dev = 0; dev < 32; dev++) {
> +			base = vmd->cfgbar + PCIE_ECAM_OFFSET(bus,
> +						PCI_DEVFN(dev, 0), 0);
> +
> +			hdr_type = readb(base + PCI_HEADER_TYPE) &
> +					 PCI_HEADER_TYPE_MASK;
> +
> +			functions = !!(hdr_type & 0x80) ? 8 : 1;
> +			for (fn = 0; fn < functions; fn++) {
> +				base = vmd->cfgbar + PCIE_ECAM_OFFSET(bus,
> +						PCI_DEVFN(dev, fn), 0);
> +
> +				hdr_type = readb(base + PCI_HEADER_TYPE) &
> +						PCI_HEADER_TYPE_MASK;
> +
> +				if (hdr_type != PCI_HEADER_TYPE_BRIDGE ||
> +				    (readw(base + PCI_CLASS_DEVICE) !=
> +				     PCI_CLASS_BRIDGE_PCI))
> +					continue;
> +
> +				memset_io(base + PCI_IO_BASE, 0,
> +					  PCI_ROM_ADDRESS1 - PCI_IO_BASE);
> +			}
> +		}
> +	}
> +}
> +
>  static void vmd_attach_resources(struct vmd_dev *vmd)
>  {
>  	vmd->dev->resource[VMD_MEMBAR1].child = &vmd->resources[1];
> @@ -801,6 +835,9 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>  	vmd_acpi_begin();
>  
>  	pci_scan_child_bus(vmd->bus);
> +	vmd_domain_reset(vmd);
> +	list_for_each_entry(child, &vmd->bus->children, node)
> +		pci_reset_bus(child->self);
>  	pci_assign_unassigned_bus_resources(vmd->bus);
>  
>  	/*

Hi Lorenzo,
Please let me know if you are okay with these changes. Thanks.