[PATCH v2] PCI: vmd: Honor ACPI _OSC on PCIe features

[PATCH v2] PCI: vmd: Honor ACPI _OSC on PCIe features

[Kai-Heng Feng]

When Samsung PCIe Gen4 NVMe is connected to Intel ADL VMD, the
combination causes AER message flood and drags the system performance
down.

The issue doesn't happen when VMD mode is disabled in BIOS, since AER
isn't enabled by acpi_pci_root_create() . When VMD mode is enabled, AER
is enabled regardless of _OSC:
[    0.410076] acpi PNP0A08:00: _OSC: platform does not support [AER]
...
[    1.486704] pcieport 10000:e0:06.0: AER: enabled with IRQ 146

Since VMD is an aperture to regular PCIe root ports, honor ACPI _OSC to
disable PCIe features accordingly to resolve the issue.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215027
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
v2:
 - Use pci_find_host_bridge() instead of open coding.

 drivers/pci/controller/vmd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index a45e8e59d3d48..acf847cb825c0 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -671,6 +671,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 	resource_size_t offset[2] = {0};
 	resource_size_t membar2_offset = 0x2000;
 	struct pci_bus *child;
+	struct pci_host_bridge *root_bridge, *vmd_bridge;
 	int ret;
 
 	/*
@@ -798,6 +799,17 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
 		return -ENODEV;
 	}
 
+	vmd_bridge = to_pci_host_bridge(vmd->bus->bridge);
+
+	root_bridge = pci_find_host_bridge(vmd->dev->bus);
+
+	vmd_bridge->native_pcie_hotplug = root_bridge->native_pcie_hotplug;
+	vmd_bridge->native_shpc_hotplug = root_bridge->native_shpc_hotplug;
+	vmd_bridge->native_aer = root_bridge->native_aer;
+	vmd_bridge->native_pme = root_bridge->native_pme;
+	vmd_bridge->native_ltr = root_bridge->native_ltr;
+	vmd_bridge->native_dpc = root_bridge->native_dpc;
+
 	vmd_attach_resources(vmd);
 	if (vmd->irq_domain)
 		dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
-- 
2.32.0

Re: [PATCH v2] PCI: vmd: Honor ACPI _OSC on PCIe features

[Rafael J. Wysocki]

On Thu, Dec 2, 2021 at 4:05 AM Kai-Heng Feng
<kai.heng.feng@canonical.com> wrote:
>
> When Samsung PCIe Gen4 NVMe is connected to Intel ADL VMD, the
> combination causes AER message flood and drags the system performance
> down.
>
> The issue doesn't happen when VMD mode is disabled in BIOS, since AER
> isn't enabled by acpi_pci_root_create() . When VMD mode is enabled, AER
> is enabled regardless of _OSC:
> [    0.410076] acpi PNP0A08:00: _OSC: platform does not support [AER]
> ...
> [    1.486704] pcieport 10000:e0:06.0: AER: enabled with IRQ 146
>
> Since VMD is an aperture to regular PCIe root ports, honor ACPI _OSC to
> disable PCIe features accordingly to resolve the issue.
>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215027
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> v2:
>  - Use pci_find_host_bridge() instead of open coding.
>
>  drivers/pci/controller/vmd.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index a45e8e59d3d48..acf847cb825c0 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -671,6 +671,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>         resource_size_t offset[2] = {0};
>         resource_size_t membar2_offset = 0x2000;
>         struct pci_bus *child;
> +       struct pci_host_bridge *root_bridge, *vmd_bridge;
>         int ret;
>
>         /*
> @@ -798,6 +799,17 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>                 return -ENODEV;
>         }
>
> +       vmd_bridge = to_pci_host_bridge(vmd->bus->bridge);
> +
> +       root_bridge = pci_find_host_bridge(vmd->dev->bus);
> +
> +       vmd_bridge->native_pcie_hotplug = root_bridge->native_pcie_hotplug;
> +       vmd_bridge->native_shpc_hotplug = root_bridge->native_shpc_hotplug;
> +       vmd_bridge->native_aer = root_bridge->native_aer;
> +       vmd_bridge->native_pme = root_bridge->native_pme;
> +       vmd_bridge->native_ltr = root_bridge->native_ltr;
> +       vmd_bridge->native_dpc = root_bridge->native_dpc;

One more, arguably minor, thing: I would put the above copying into a
separate function and call it here and I would add a comment
explaining why it is done next to it, like

/*
 * Since VMD is an aperture to regular PCIe root ports, only allow it to control
 * features that the OS is allowed to control on the physical PCI bus.
 */
vmd_copy_host_bridge_flags(to_pci_host_bridge(vmd->bus->bridge),
pci_find_host_bridge(vmd->dev->bus));

> +
>         vmd_attach_resources(vmd);
>         if (vmd->irq_domain)
>                 dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
> --
> 2.32.0
>