Re: [PATCH v13 22/24] virt: gunyah: Add irqfd interface

From: Alex Elder <elder@linaro.org>
To: Elliot Berman <quic_eberman@quicinc.com>,
	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
	Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>,
	Jonathan Corbet <corbet@lwn.net>
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>,
	Will Deacon <will@kernel.org>, Andy Gross <agross@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	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 v13 22/24] virt: gunyah: Add irqfd interface
Date: Mon, 5 Jun 2023 14:50:32 -0500	[thread overview]
Message-ID: <1c386f4e-e2dd-eb79-9117-9b19877f2ccc@linaro.org> (raw)
In-Reply-To: <20230509204801.2824351-23-quic_eberman@quicinc.com>

On 5/9/23 3:47 PM, Elliot Berman wrote:
> Enable support for creating irqfds which can raise an interrupt on a
> Gunyah virtual machine. irqfds are exposed to userspace as a Gunyah VM
> function with the name "irqfd". If the VM devicetree is not configured
> to create a doorbell with the corresponding label, userspace will still
> be able to assert the eventfd but no interrupt will be raised on the
> guest.
> 
> Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>

I have a minor suggestion.  I think I'd like to look at this
again, so:

Acked-by: Alex Elder <elder@linaro.org>

> ---
>   Documentation/virt/gunyah/vm-manager.rst |   2 +-
>   drivers/virt/gunyah/Kconfig              |   9 ++
>   drivers/virt/gunyah/Makefile             |   1 +
>   drivers/virt/gunyah/gunyah_irqfd.c       | 180 +++++++++++++++++++++++
>   include/uapi/linux/gunyah.h              |  35 +++++
>   5 files changed, 226 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/virt/gunyah/gunyah_irqfd.c
> 

. . .

> @@ -99,6 +102,38 @@ struct gh_fn_vcpu_arg {
>   	__u32 id;
>   };
>   
> +/**
> + * enum gh_irqfd_flags - flags for use in gh_fn_irqfd_arg
> + * @GH_IRQFD_FLAGS_LEVEL: make the interrupt operate like a level triggered
> + *                        interrupt on guest side. Triggering IRQFD before
> + *                        guest handles the interrupt causes interrupt to
> + *                        stay asserted.
> + */
> +enum gh_irqfd_flags {
> +	GH_IRQFD_FLAGS_LEVEL		= 1UL << 0,

	BIT(0),			/* ? */

> +};
> +
> +/**
> + * struct gh_fn_irqfd_arg - Arguments to create an irqfd function.
> + *
> + * Create this function with &GH_VM_ADD_FUNCTION using type &GH_FN_IRQFD.
> + *
> + * Allows setting an eventfd to directly trigger a guest interrupt.
> + * irqfd.fd specifies the file descriptor to use as the eventfd.
> + * irqfd.label corresponds to the doorbell label used in the guest VM's devicetree.
> + *
> + * @fd: an eventfd which when written to will raise a doorbell
> + * @label: Label of the doorbell created on the guest VM
> + * @flags: see &enum gh_irqfd_flags
> + * @padding: padding bytes
> + */
> +struct gh_fn_irqfd_arg {
> +	__u32 fd;
> +	__u32 label;
> +	__u32 flags;
> +	__u32 padding;
> +};
> +
>   /**
>    * struct gh_fn_desc - Arguments to create a VM function
>    * @type: Type of the function. See &enum gh_fn_type.