From: Nuno Das Neves <nunodasneves@linux.microsoft.com>
To: Greg KH <gregkh@linuxfoundation.org>, Wei Liu <wei.liu@kernel.org>
Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, linux-arm-kernel@lists.infradead.org,
linux-arch@vger.kernel.org, patches@lists.linux.dev,
mikelley@microsoft.com, kys@microsoft.com,
haiyangz@microsoft.com, decui@microsoft.com,
apais@linux.microsoft.com, Tianyu.Lan@microsoft.com,
ssengar@linux.microsoft.com, mukeshrathor@microsoft.com,
stanislav.kinsburskiy@gmail.com, jinankjain@linux.microsoft.com,
vkuznets@redhat.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
will@kernel.org, catalin.marinas@arm.com
Subject: Re: [PATCH v3 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V
Date: Tue, 26 Sep 2023 14:52:36 -0700 [thread overview]
Message-ID: <05119cbc-155d-47c5-ab21-e6a08eba5dc4@linux.microsoft.com> (raw)
In-Reply-To: <2023092646-version-series-a7b5@gregkh>
On 9/26/2023 1:03 AM, Greg KH wrote:
> On Tue, Sep 26, 2023 at 07:00:51AM +0000, Wei Liu wrote:
>> On Tue, Sep 26, 2023 at 08:31:03AM +0200, Greg KH wrote:
>>> On Tue, Sep 26, 2023 at 05:54:34AM +0000, Wei Liu wrote:
>>>> On Tue, Sep 26, 2023 at 06:52:46AM +0200, Greg KH wrote:
>>>>> On Mon, Sep 25, 2023 at 05:07:24PM -0700, Nuno Das Neves wrote:
>>>>>> On 9/23/2023 12:58 AM, Greg KH wrote:
>>>>>>> Also, drivers should never call pr_*() calls, always use the proper
>>>>>>> dev_*() calls instead.
>>>>>>>
>>>>>>
>>>>>> We only use struct device in one place in this driver, I think that is the
>>>>>> only place it makes sense to use dev_*() over pr_*() calls.
>>>>>
>>>>> Then the driver needs to be fixed to use struct device properly so that
>>>>> you do have access to it when you want to print messages. That's a
>>>>> valid reason to pass around your device structure when needed.
>>>>
What is the tangible benefit of using dev_*() over pr_*()? As I said,
our use of struct device is very limited compared to all the places we
may need to log errors.
pr_*() is used by many, many drivers; it seems to be the norm. We can
certainly add a pr_fmt to improve the logging.
>>>> Greg, ACRN and Nitro drivers do not pass around the device structure.
>>>> Instead, they rely on a global struct device. We can follow the same.
>>>
>>> A single global struct device is wrong, please don't do that.
>>>
>>> Don't copy bad design patterns from other drivers, be better :)
>>>
What makes it a bad pattern? It seems to be well-established, and is
also used by KVM which this driver is loosely modeled after:
https://elixir.bootlin.com/linux/v6.5.5/source/virt/kvm/kvm_main.c#L5128
>>
>> If we're working with real devices like network cards or graphics cards
>> I would agree -- it is easy to imagine that we have several cards of the
>> same model in the system -- but in real world there won't be two
>> hypervisor instances running on the same hardware.
>>
>> We can stash the struct device inside some private data fields, but that
>> doesn't change the fact that we're still having one instance of the
>> structure. Is this what you want? Or do you have something else in mind?
>
> You have a real device, it's how userspace interacts with your
> subsystem. Please use that, it is dynamically created and handled and
> is the correct representation here.
>
Are you referring to the struct device we get from calling
misc_register? If not, please be more specific.
How would you suggest we get a reference to that device via e.g. open()
or ioctl() without keeping a global reference to it?
Thanks,
Nuno
next prev parent reply other threads:[~2023-09-26 21:52 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-22 18:38 [PATCH v3 00/15] Introduce /dev/mshv drivers Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 01/15] hyperv-tlfs: Change shared HV_REGISTER_* defines to HV_MSR_* Nuno Das Neves
2023-09-22 18:52 ` Wei Liu
2023-09-22 18:38 ` [PATCH v3 02/15] mshyperv: Introduce hv_get_hypervisor_version function Nuno Das Neves
2023-09-22 18:53 ` Wei Liu
2023-09-22 18:38 ` [PATCH v3 03/15] mshyperv: Introduce numa_node_to_proximity_domain_info Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 04/15] asm-generic/mshyperv: Introduce hv_recommend_using_aeoi() Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 05/15] hyperv: Move hv_connection_id to hyperv-tlfs Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 06/15] hyperv-tlfs: Introduce hv_status_to_string and hv_status_to_errno Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 07/15] Drivers: hv: Move hv_call_deposit_pages and hv_call_create_vp to common code Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 08/15] Drivers: hv: Introduce per-cpu event ring tail Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 09/15] Drivers: hv: Introduce hv_output_arg_exists in hv_common.c Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 10/15] x86: hyperv: Add mshv_handler irq handler and setup function Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 11/15] Drivers: hv: export vmbus_isr, hv_context and hv_post_message Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 12/15] Documentation: Reserve ioctl number for mshv driver Nuno Das Neves
2023-09-22 18:48 ` Wei Liu
2023-09-22 18:38 ` [PATCH v3 13/15] uapi: hyperv: Add mshv driver headers defining hypervisor ABIs Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 14/15] asm-generic: hyperv: Use new Hyper-V headers conditionally Nuno Das Neves
2023-09-22 18:38 ` [PATCH v3 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V Nuno Das Neves
2023-09-22 20:02 ` Wei Liu
2023-09-23 7:56 ` Greg KH
2023-09-23 20:58 ` Wei Liu
2023-09-24 4:48 ` Saurabh Singh Sengar
2023-09-23 7:58 ` Greg KH
2023-09-26 0:07 ` Nuno Das Neves
2023-09-26 4:52 ` Greg KH
2023-09-26 5:54 ` Wei Liu
2023-09-26 6:31 ` Greg KH
2023-09-26 7:00 ` Wei Liu
2023-09-26 8:03 ` Greg KH
2023-09-26 21:52 ` Nuno Das Neves [this message]
2023-09-27 6:01 ` Greg KH
2023-09-27 8:04 ` Wei Liu
2023-09-27 8:33 ` Greg KH
2023-09-28 0:17 ` Nuno Das Neves
2023-09-26 12:33 ` Saurabh Singh Sengar
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