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Date: Thu, 30 Nov 2023 10:03:02 -0500
From: Stewart Hildebrand <stewart.hildebrand@....com>
To: "Chen, Jiqian" <Jiqian.Chen@....com>,
Stefano Stabellini <sstabellini@...nel.org>
CC: Juergen Gross <jgross@...e.com>,
Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
Thomas Gleixner <tglx@...utronix.de>,
"Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Len Brown <lenb@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Roger Pau Monné <roger.pau@...rix.com>,
"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"Stabellini, Stefano" <stefano.stabellini@....com>,
"Deucher, Alexander" <Alexander.Deucher@....com>,
"Koenig, Christian" <Christian.Koenig@....com>,
"Ragiadakou, Xenia" <Xenia.Ragiadakou@....com>,
"Huang, Honglei1" <Honglei1.Huang@....com>,
"Zhang, Julia" <Julia.Zhang@....com>,
"Huang, Ray" <Ray.Huang@....com>
Subject: Re: [RFC KERNEL PATCH v2 1/3] xen/pci: Add xen_reset_device_state
function
On 11/30/23 02:03, Chen, Jiqian wrote:
>
> On 2023/11/30 11:46, Stefano Stabellini wrote:
>> On Fri, 24 Nov 2023, Jiqian Chen wrote:
>>> When device on dom0 side has been reset, the vpci on Xen side
>>> won't get notification, so that the cached state in vpci is
>>> all out of date with the real device state.
>>> To solve that problem, this patch add a function to clear all
>>> vpci device state when device is reset on dom0 side.
>>>
>>> And call that function in pcistub_init_device. Because when
>>> we use "pci-assignable-add" to assign a passthrough device in
>>> Xen, it will reset passthrough device and the vpci state will
>>> out of date, and then device will fail to restore bar state.
>>>
>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@....com>
>>> Signed-off-by: Huang Rui <ray.huang@....com>
>>> ---
>>> drivers/xen/pci.c | 12 ++++++++++++
>>> drivers/xen/xen-pciback/pci_stub.c | 3 +++
>>> include/xen/interface/physdev.h | 2 ++
>>> include/xen/pci.h | 6 ++++++
>>> 4 files changed, 23 insertions(+)
>>>
>>> diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
>>> index 72d4e3f193af..e9b30bc09139 100644
>>> --- a/drivers/xen/pci.c
>>> +++ b/drivers/xen/pci.c
>>> @@ -177,6 +177,18 @@ static int xen_remove_device(struct device *dev)
>>> return r;
>>> }
>>>
>>> +int xen_reset_device_state(const struct pci_dev *dev)
>>> +{
>>> + struct physdev_pci_device device = {
>>> + .seg = pci_domain_nr(dev->bus),
>>> + .bus = dev->bus->number,
>>> + .devfn = dev->devfn
>>> + };
>>> +
>>> + return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_state_reset, &device);
>>> +}
>>> +EXPORT_SYMBOL_GPL(xen_reset_device_state);
>>> +
>>> static int xen_pci_notifier(struct notifier_block *nb,
>>> unsigned long action, void *data)
>>> {
>>> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
>>> index e34b623e4b41..5a96b6c66c07 100644
>>> --- a/drivers/xen/xen-pciback/pci_stub.c
>>> +++ b/drivers/xen/xen-pciback/pci_stub.c
>>> @@ -421,6 +421,9 @@ static int pcistub_init_device(struct pci_dev *dev)
>>> else {
>>> dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");
>>> __pci_reset_function_locked(dev);
>>> + err = xen_reset_device_state(dev);
>>> + if (err)
>>> + goto config_release;
>>
>> Older versions of Xen won't have the hypercall
>> PHYSDEVOP_pci_device_state_reset implemented. I think we should do
>> something like:
>>
>> if (err && xen_pvh_domain())
>> goto config_release;
>>
>>
>> Or even:
>>
>> if (xen_pvh_domain()) {
>> err = xen_reset_device_state(dev);
>> if (err)
>> goto config_release;
>> }
>>
>> depending on whether we want to call xen_reset_device_state also for PV
>> guests or not. I am assuming we don't want to error out on failure such
>> as -ENOENT for PV guests.
> Yes, only for PVH dom0, I will add the condition in next version. Thank you!
We will want to call xen_reset_device_state() for Arm dom0, too, so checking xen_pvh_domain() alone is not sufficient. I suggest instead to check !xen_pv_domain().
>
>>
>>
>>> pci_restore_state(dev);
>>> }
>>> /* Now disable the device (this also ensures some private device
>>> diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
>>> index a237af867873..231526f80f6c 100644
>>> --- a/include/xen/interface/physdev.h
>>> +++ b/include/xen/interface/physdev.h
>>> @@ -263,6 +263,8 @@ struct physdev_pci_device {
>>> uint8_t devfn;
>>> };
>>>
>>> +#define PHYSDEVOP_pci_device_state_reset 32
>>> +
>>> #define PHYSDEVOP_DBGP_RESET_PREPARE 1
>>> #define PHYSDEVOP_DBGP_RESET_DONE 2
>>>
>>> diff --git a/include/xen/pci.h b/include/xen/pci.h
>>> index b8337cf85fd1..b2e2e856efd6 100644
>>> --- a/include/xen/pci.h
>>> +++ b/include/xen/pci.h
>>> @@ -4,10 +4,16 @@
>>> #define __XEN_PCI_H__
>>>
>>> #if defined(CONFIG_XEN_DOM0)
>>> +int xen_reset_device_state(const struct pci_dev *dev);
>>> int xen_find_device_domain_owner(struct pci_dev *dev);
>>> int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain);
>>> int xen_unregister_device_domain_owner(struct pci_dev *dev);
>>> #else
>>> +static inline int xen_reset_device_state(const struct pci_dev *dev)
>>> +{
>>> + return -1;
>>> +}
>>> +
>>> static inline int xen_find_device_domain_owner(struct pci_dev *dev)
>>> {
>>> return -1;
>>> --
>>> 2.34.1
>>>
>
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