linux-kernel - Re: [PATCH v9 27/27] virt: gunyah: Add ioeventfd

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Date:   Tue, 7 Feb 2023 14:19:54 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Elliot Berman <quic_eberman@...cinc.com>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Alex Elder <elder@...aro.org>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Jonathan Corbet <corbet@....net>
Cc:     Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Sudeep Holla <sudeep.holla@....com>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v9 27/27] virt: gunyah: Add ioeventfd



On 20/01/2023 22:46, Elliot Berman wrote:
> Allow userspace to attach an ioeventfd to an mmio address within the guest.
> 
> Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>
> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>
> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
> ---
>   Documentation/virt/gunyah/vm-manager.rst |  21 +++++
>   drivers/virt/gunyah/Kconfig              |   9 ++
>   drivers/virt/gunyah/Makefile             |   1 +
>   drivers/virt/gunyah/gunyah_ioeventfd.c   | 109 +++++++++++++++++++++++
>   include/uapi/linux/gunyah.h              |  10 +++
>   5 files changed, 150 insertions(+)
>   create mode 100644 drivers/virt/gunyah/gunyah_ioeventfd.c

> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
> index a947f0317ca9..3cc387f0831a 100644
> --- a/include/uapi/linux/gunyah.h
> +++ b/include/uapi/linux/gunyah.h
> @@ -65,11 +65,21 @@ struct gh_fn_irqfd_arg {
>   	__u32 flags;
>   };
>   
> +struct gh_fn_ioeventfd_arg {
> +	__u64 datamatch;
> +	__u64 addr;        /* legal mmio address */
> +	__u32 len;         /* 1, 2, 4, or 8 bytes; or 0 to ignore length */
> +	__s32 fd;
> +#define GH_IOEVENTFD_DATAMATCH		(1UL << 0)
> +	__u32 flags;

This is not naturally aligned, consider adding a reserved __u32 field to 
be able to make this compatible with both 32 and 64 bit machines.

I see few other uapi structures that suffer exact same issue.

--srini

> +};
> +
>   struct gh_vm_function {
>   	char name[GUNYAH_FUNCTION_NAME_SIZE];
>   	union {
>   		struct gh_fn_vcpu_arg vcpu;
>   		struct gh_fn_irqfd_arg irqfd;
> +		struct gh_fn_ioeventfd_arg ioeventfd;
>   		char data[GUNYAH_FUNCTION_MAX_ARG_SIZE];
>   	};
>   };