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

[Colin Xu]

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