From: Elliot Berman <quic_eberman@quicinc.com>
To: Alex Elder <elder@linaro.org>,
Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>,
Jonathan Corbet <corbet@lwn.net>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>
Cc: Murali Nalajala <quic_mnalajal@quicinc.com>,
Trilok Soni <quic_tsoni@quicinc.com>,
Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
Carl van Schaik <quic_cvanscha@quicinc.com>,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
Bjorn Andersson <andersson@kernel.org>,
"Konrad Dybcio" <konrad.dybcio@linaro.org>,
Arnd Bergmann <arnd@arndb.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Bagas Sanjaya <bagasdotme@gmail.com>,
Andy Gross <agross@kernel.org>,
Jassi Brar <jassisinghbrar@gmail.com>,
<linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-doc@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v11 22/26] virt: gunyah: Add proxy-scheduled vCPUs
Date: Tue, 18 Apr 2023 10:18:12 -0700 [thread overview]
Message-ID: <6d7ddd2c-526c-a131-1012-c09032579824@quicinc.com> (raw)
In-Reply-To: <274ad221-f397-b634-5742-fe6c9cb18843@quicinc.com>
On 4/17/2023 3:41 PM, Elliot Berman wrote:
>
>
> On 3/31/2023 7:27 AM, Alex Elder wrote:
>> On 3/3/23 7:06 PM, Elliot Berman wrote:
>
> [snip]
>
>>> diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
>>> index caeb3b3a3e9a..e52265fa5715 100644
>>> --- a/include/uapi/linux/gunyah.h
>>> +++ b/include/uapi/linux/gunyah.h
>>> @@ -62,8 +62,32 @@ struct gh_vm_dtb_config {
>>> #define GH_VM_START _IO(GH_IOCTL_TYPE, 0x3)
>>> +/**
>>> + * GH_FN_VCPU - create a vCPU instance to control a vCPU
>>> + *
>>> + * gh_fn_desc is filled with &struct gh_fn_vcpu_arg
>>> + *
>>> + * The vcpu type will register with the VM Manager to expect to control
>>> + * vCPU number `vcpu_id`. It returns a file descriptor allowing
>>> interaction with
>>> + * the vCPU. See the Gunyah vCPU API description sections for
>>> interacting with
>>> + * the Gunyah vCPU file descriptors.
>>> + *
>>> + * Return: file descriptor to manipulate the vcpu. See GH_VCPU_* ioctls
>>> + */
>>> +#define GH_FN_VCPU 1
>>
>> I think you should define GH_VN_VCPU, GN_FN_IRQFD, and GN_FN_IOEVENTFD
>> in an enumerated type. Each has a type associated with it, and you can
>> add the explanation for the function in the kernel-doc comments above
>> thosse type definitions.
>>
>
> I'd like to enumify the GH_FN_* macros, but one challenge I'm facing is
> that it breaks the module alias implementation in patch 19.
>
> MODULE_ALIAS("ghfunc:"__stringify(_type))
>
> When the GH_FN_* are regular preprocessor macros backed by an integer,
> the preprocessor will make the module alias ghfunc:0 (or ghfunc:1, etc).
> This works well because I can do
>
> request_module("ghfunc:%d", type);
>
> If the function hasn't been registered and then gunyah_vcpu.ko gets
> loaded automatically.
>
> With enum, compiler knows the value of GH_FN_VCPU and preprocessor will
> make the module alias like ghfunc:GH_FN_VCPU.
>
I still like the idea of having enum for documentation and clarity. I
noticed that nfnetlink.h saw the same problem for NFNL_SUBSYS_*.
Is this compromise terrible and I should give up on the enum?
enum gh_fn_type {
/* _GH_FN_* macro required for MODULE_ALIAS, otherwise __stringify() trick
* won't work anymore */
#define _GH_FN_VCPU 1
GH_FN_VCPU = _GH_FN_VCPU,
#define _GH_FN_IRQFD 2
GH_FN_IRQFD = _GH_FN_IRQFD,
#define _GH_FN_IOEVENTFD 3
GH_FN_IOEVENTFD = _GH_FN_IOEVENTFD,
};
> [snip]
>
>>> +
>>> +/*
>>> + * Gunyah presently sends max 4 bytes of exit_reason.
>>> + * If that changes, this macro can be safely increased without breaking
>>> + * userspace so long as struct gh_vcpu_run < PAGE_SIZE.
>>
>> Is PAGE_SIZE allowed to be anything other than 4096 bytes? Do you
>> expect this driver to work properly if the page size were configured
>> to be 16384 bytes? In other words, is this a Gunyah constant, or
>> is it *really* the page size configured for Linux?
>>
>
> Our implementations are only doing 4096 bytes. I expect the driver to
> work properly when using 16k pages. This really is a Linux page. It's a
> reflection of the alloc_page in gh_vcpu_bind().
>
> The exit reason is copied from hypervisor into field accessible by
> userspace directly. Gunyah makes the exit reason size dynamic -- there's
> no architectural limitation preventing the exit reason from being a
> string or some lengthy data.
>
> As I was writing this response, I realized that I should be able to make
> this a zero-length array and ensure that reason[] doesn't overflow
> PAGE_SIZE...
>
> The comment was trying to explain that Linux itself imposes a limitation
> on the maximum exit reason size. If we need to support longer exit
> reason, we're OK to do so long as the total size doesn't overrun
> PAGE_SIZE. There aren't any plans to need longer exit reasons than the 8
> bytes mentioned today.
>
> Thanks,
> Elliot
next prev parent reply other threads:[~2023-04-18 17:18 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-04 1:06 [PATCH v11 00/26] Drivers for gunyah hypervisor Elliot Berman
2023-03-04 1:06 ` [PATCH v11 01/26] docs: gunyah: Introduce Gunyah Hypervisor Elliot Berman
2023-03-04 1:06 ` [PATCH v11 02/26] dt-bindings: Add binding for gunyah hypervisor Elliot Berman
2023-03-04 1:06 ` [PATCH v11 03/26] gunyah: Common types and error codes for Gunyah hypercalls Elliot Berman
2023-03-21 14:23 ` Srinivas Kandagatla
2023-03-31 14:24 ` Alex Elder
2023-04-03 19:44 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 04/26] virt: gunyah: Add hypercalls to identify Gunyah Elliot Berman
2023-03-21 14:22 ` Srinivas Kandagatla
2023-03-31 14:24 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 05/26] virt: gunyah: Identify hypervisor version Elliot Berman
2023-03-21 15:48 ` Srinivas Kandagatla
2023-03-31 14:24 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 06/26] virt: gunyah: msgq: Add hypercalls to send and receive messages Elliot Berman
2023-03-21 15:49 ` Srinivas Kandagatla
2023-03-31 14:25 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 07/26] mailbox: Add Gunyah message queue mailbox Elliot Berman
2023-03-21 14:22 ` Srinivas Kandagatla
2023-03-31 14:25 ` Alex Elder
2023-04-03 20:15 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 08/26] gunyah: rsc_mgr: Add resource manager RPC core Elliot Berman
2023-03-31 14:25 ` Alex Elder
2023-04-03 20:34 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 09/26] gunyah: rsc_mgr: Add VM lifecycle RPC Elliot Berman
2023-03-31 14:25 ` Alex Elder
2023-04-03 21:09 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 10/26] gunyah: vm_mgr: Introduce basic VM Manager Elliot Berman
2023-03-21 14:23 ` Srinivas Kandagatla
2023-03-31 14:25 ` Alex Elder
2023-04-11 20:48 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 11/26] gunyah: rsc_mgr: Add RPC for sharing memory Elliot Berman
2023-03-31 14:26 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 12/26] gunyah: vm_mgr: Add/remove user memory regions Elliot Berman
2023-03-24 18:37 ` Will Deacon
2023-04-11 20:34 ` Elliot Berman
2023-04-11 21:19 ` Will Deacon
2023-04-12 20:48 ` Elliot Berman
2023-04-13 9:54 ` Will Deacon
2023-03-31 14:26 ` Alex Elder
2023-04-11 21:04 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 13/26] gunyah: vm_mgr: Add ioctls to support basic non-proxy VM boot Elliot Berman
2023-03-21 14:24 ` Srinivas Kandagatla
2023-04-11 21:07 ` Elliot Berman
2023-04-11 21:09 ` Alex Elder
2023-03-31 14:26 ` Alex Elder
2023-04-11 21:16 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 14/26] samples: Add sample userspace Gunyah VM Manager Elliot Berman
2023-03-31 14:26 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 15/26] gunyah: rsc_mgr: Add platform ops on mem_lend/mem_reclaim Elliot Berman
2023-03-21 14:23 ` Srinivas Kandagatla
2023-03-22 19:17 ` Elliot Berman
2023-03-31 14:26 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 16/26] firmware: qcom_scm: Register Gunyah platform ops Elliot Berman
2023-03-21 14:24 ` Srinivas Kandagatla
2023-03-21 18:40 ` Elliot Berman
2023-03-21 20:19 ` Srinivas Kandagatla
2023-03-04 1:06 ` [PATCH v11 17/26] docs: gunyah: Document Gunyah VM Manager Elliot Berman
2023-03-04 1:06 ` [PATCH v11 18/26] virt: gunyah: Translate gh_rm_hyp_resource into gunyah_resource Elliot Berman
2023-03-31 14:26 ` Alex Elder
2023-04-18 0:25 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 19/26] gunyah: vm_mgr: Add framework to add VM Functions Elliot Berman
2023-03-31 14:26 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 20/26] virt: gunyah: Add resource tickets Elliot Berman
2023-03-31 14:27 ` Alex Elder
2023-04-17 22:57 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 21/26] virt: gunyah: Add IO handlers Elliot Berman
2023-03-31 14:27 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 22/26] virt: gunyah: Add proxy-scheduled vCPUs Elliot Berman
2023-03-31 14:27 ` Alex Elder
2023-04-17 22:41 ` Elliot Berman
2023-04-18 12:46 ` Alex Elder
2023-04-18 17:18 ` Elliot Berman [this message]
2023-04-18 17:31 ` Alex Elder
2023-04-18 18:35 ` Elliot Berman
2023-03-04 1:06 ` [PATCH v11 23/26] virt: gunyah: Add hypercalls for sending doorbell Elliot Berman
2023-03-31 14:27 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 24/26] virt: gunyah: Add irqfd interface Elliot Berman
2023-03-31 14:27 ` Alex Elder
2023-04-17 22:55 ` Elliot Berman
2023-04-18 12:55 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 25/26] virt: gunyah: Add ioeventfd Elliot Berman
2023-03-31 14:27 ` Alex Elder
2023-03-04 1:06 ` [PATCH v11 26/26] MAINTAINERS: Add Gunyah hypervisor drivers section Elliot Berman
2023-03-31 14:24 ` [PATCH v11 00/26] Drivers for gunyah hypervisor Alex Elder
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