Re: [RFC PATCH] vfio/pci: Allow force needs_pm_restore as specified by device:vendor

Colin Xu <Colin.Xu@xxxxxxxxx> · Fri, 27 Nov 2020 11:53:39 +0800

On 11/25/20 11:53 PM, Alex Williamson wrote:
On Wed, 25 Nov 2020 10:18:24 +0800
Colin Xu <colin.xu@xxxxxxxxx> wrote:

Force specific device listed in params pm_restore_ids to follow
device state save/restore as needs_pm_restore.
Some device has NoSoftRst so will skip current state save/restore enabled
by needs_pm_restore. However once the device experienced power state
D3<->D0 transition, either by idle_d3 or the guest driver changes PM_CTL,
the guest driver won't get correct devie state although the configure
space doesn't change.
It sounds like you're describing a device that incorrectly exposes
NoSoftRst when there is in fact some sort of internal reset that
requires reprogramming config space.  What device requires this?  How
is a user to know when this option is required?  It seems like this
would be better handled via a quirk in PCI core that sets a device flag
that the NoSoftRst value is incorrect for the specific affected
devices.  Thanks,

Alex

Thanks for the feedback.

The device found are: Comet Lake PCH Serial IO I2C Controller
[8086:06e8]
[8086:06e9]

Yes you're right, there is no straight way for user to know the device. 
The above device I found is during pass through them to VM. Although 
adding such param may help in certain scenario, it still too 
device-specific but not common in most cases.

I'll try the pci quirk way.

Colin



Cc: Swee Yee Fonn <swee.yee.fonn@xxxxxxxxx>
Signed-off-by: Colin Xu <colin.xu@xxxxxxxxx>
---
  drivers/vfio/pci/vfio_pci.c | 66 ++++++++++++++++++++++++++++++++++++-
  1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index e6190173482c..50a4141c9e1d 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -34,6 +34,15 @@
  #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@xxxxxxxxxx>"
  #define DRIVER_DESC     "VFIO PCI - User Level meta-driver"
  
+#define VFIO_MAX_PM_DEV 32
+struct vfio_pm_devs {
+	struct {
+		unsigned short  vendor;
+		unsigned short  device;
+	} ids[VFIO_MAX_PM_DEV];
+	u32 count;
+};
+
  static char ids[1024] __initdata;
  module_param_string(ids, ids, sizeof(ids), 0);
  MODULE_PARM_DESC(ids, "Initial PCI IDs to add to the vfio driver, format is \"vendor:device[:subvendor[:subdevice[:class[:class_mask]]]]\" and multiple comma separated entries can be specified");
@@ -64,6 +73,10 @@ static bool disable_denylist;
  module_param(disable_denylist, bool, 0444);
  MODULE_PARM_DESC(disable_denylist, "Disable use of device denylist. Disabling the denylist allows binding to devices with known errata that may lead to exploitable stability or security issues when accessed by untrusted users.");
  
+static char pm_restore_ids[1024] __initdata;
+module_param_string(pm_restore_ids, pm_restore_ids, sizeof(pm_restore_ids), 0);
+MODULE_PARM_DESC(pm_restore_ids, "comma separated device in format of \"vendor:device\"");
+
  static inline bool vfio_vga_disabled(void)
  {
  #ifdef CONFIG_VFIO_PCI_VGA
@@ -260,10 +273,50 @@ static bool vfio_pci_nointx(struct pci_dev *pdev)
  	return false;
  }
  
+static struct vfio_pm_devs pm_devs = {0};
+static void __init vfio_pci_fill_pm_ids(void)
+{
+	char *p, *id;
+	int idx = 0;
+
+	/* no ids passed actually */
+	if (pm_restore_ids[0] == '\0')
+		return;
+
+	/* add ids specified in the module parameter */
+	p = pm_restore_ids;
+	while ((id = strsep(&p, ","))) {
+		unsigned int vendor, device = PCI_ANY_ID;
+		int fields;
+
+		if (!strlen(id))
+			continue;
+
+		fields = sscanf(id, "%x:%x", &vendor, &device);
+
+		if (fields != 2) {
+			pr_warn("invalid vendor:device string \"%s\"\n", id);
+			continue;
+		}
+
+		if (idx < VFIO_MAX_PM_DEV) {
+			pm_devs.ids[idx].vendor = vendor;
+			pm_devs.ids[idx].device = device;
+			pm_devs.count++;
+			idx++;
+			pr_info("add [%04x:%04x] for needs_pm_restore\n",
+				vendor, device);
+		} else {
+			pr_warn("Exceed maximum %d, skip adding [%04x:%04x] for needs_pm_restore\n",
+				VFIO_MAX_PM_DEV, vendor, device);
+		}
+	}
+}
+
  static void vfio_pci_probe_power_state(struct vfio_pci_device *vdev)
  {
  	struct pci_dev *pdev = vdev->pdev;
-	u16 pmcsr;
+	u16 pmcsr, idx;
  
  	if (!pdev->pm_cap)
  		return;
@@ -271,6 +324,16 @@ static void vfio_pci_probe_power_state(struct vfio_pci_device *vdev)
  	pci_read_config_word(pdev, pdev->pm_cap + PCI_PM_CTRL, &pmcsr);
  
  	vdev->needs_pm_restore = !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET);
+
+	for (idx = 0; idx < pm_devs.count; idx++) {
+		if (vdev->pdev->vendor == pm_devs.ids[idx].vendor &&
+		    vdev->pdev->device == pm_devs.ids[idx].device) {
+			vdev->needs_pm_restore = true;
+			pr_info("force [%04x:%04x] to needs_pm_restore\n",
+				vdev->pdev->vendor, vdev->pdev->device);
+			break;
+		}
+	}
  }
  
  /*
@@ -2423,6 +2486,7 @@ static int __init vfio_pci_init(void)
  		goto out_driver;
  
  	vfio_pci_fill_ids();
+	vfio_pci_fill_pm_ids();
  
  	if (disable_denylist)
  		pr_warn("device denylist disabled.\n");

--
Best Regards,
Colin Xu







