Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35;
Received-SPF: Pass (protection.outlook.com: domain of amd.com designates
 165.204.84.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C
Message-ID: <4f21ce4f-7b79-47cb-baad-e31702b8887e@amd.com>
Date:   Sun, 3 Dec 2023 22:45:30 -0500
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [RFC KERNEL PATCH v2 1/3] xen/pci: Add xen_reset_device_state
 function
Content-Language: en-US
To:     "Chen, Jiqian" <Jiqian.Chen@amd.com>,
        Stefano Stabellini <sstabellini@kernel.org>
CC:     Juergen Gross <jgross@suse.com>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= <roger.pau@citrix.com>,
        "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "Stabellini, Stefano" <stefano.stabellini@amd.com>,
        "Deucher, Alexander" <Alexander.Deucher@amd.com>,
        "Koenig, Christian" <Christian.Koenig@amd.com>,
        "Ragiadakou, Xenia" <Xenia.Ragiadakou@amd.com>,
        "Huang, Honglei1" <Honglei1.Huang@amd.com>,
        "Zhang, Julia" <Julia.Zhang@amd.com>,
        "Huang, Ray" <Ray.Huang@amd.com>
References: <20231124103123.3263471-1-Jiqian.Chen@amd.com>
 <20231124103123.3263471-2-Jiqian.Chen@amd.com>
 <alpine.DEB.2.22.394.2311291943260.3533093@ubuntu-linux-20-04-desktop>
 <BL1PR12MB58490EB260D226500141557EE782A@BL1PR12MB5849.namprd12.prod.outlook.com>
 <f78395f3-6588-4bc9-8612-3450a8f44be7@amd.com>
 <BL1PR12MB5849C9BFEBECAF3C5BCBB09DE786A@BL1PR12MB5849.namprd12.prod.outlook.com>
From:   Stewart Hildebrand <stewart.hildebrand@amd.com>
In-Reply-To: <BL1PR12MB5849C9BFEBECAF3C5BCBB09DE786A@BL1PR12MB5849.namprd12.prod.outlook.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Dec 2023 03:45:38.0130
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 99e09e39-a133-4033-c156-08dbf47b7abf
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com]
X-MS-Exchange-CrossTenant-AuthSource: MN1PEPF0000F0E5.namprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7347
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Sun, 03 Dec 2023 19:45:56 -0800 (PST)

On 12/3/23 22:25, Chen, Jiqian wrote:
> Hi Stewart,
> 
> On 2023/11/30 23:03, Stewart Hildebrand wrote:
>> 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@amd.com>
>>>>> Signed-off-by: Huang Rui <ray.huang@amd.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().
> I am not using Arm. But is Arm dom0 not a PVH type dom0?

Apparently not, Arm dom0 appears to be a xen_hvm_domain() from the kernel's perspective.

> 
>>
>>>
>>>>
>>>>
>>>>>  		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
>>>>>
>>>
>