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Reply-To: Colin.Xu@intel.com
Subject: Re: [RFC PATCH] vfio/pci: Allow force needs_pm_restore as specified
 by device:vendor
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Fonn, Swee Yee" <swee.yee.fonn@intel.com>
References: <20201125021824.27411-1-colin.xu@intel.com>
 <20201125085312.63510f9f@w520.home>
From:   Colin Xu <Colin.Xu@intel.com>
Message-ID: <7e7a83ca-8530-1afa-4b85-2ef76fb99a5c@intel.com>
Date:   Fri, 27 Nov 2020 11:53:39 +0800
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On 11/25/20 11:53 PM, Alex Williamson wrote:
> On Wed, 25 Nov 2020 10:18:24 +0800
> Colin Xu <colin.xu@intel.com> 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@intel.com>
>> Signed-off-by: Colin Xu <colin.xu@intel.com>
>> ---
>>   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@redhat.com>"
>>   #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