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

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Date:   Fri, 9 Jun 2023 11:22:34 -0700
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Alex Elder <elder@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Jonathan Corbet <corbet@....net>
CC:     Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        "Konrad Dybcio" <konrad.dybcio@...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>,
        Will Deacon <will@...nel.org>, Andy Gross <agross@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Jassi Brar <jassisinghbrar@...il.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 v13 22/24] virt: gunyah: Add irqfd interface



On 6/5/2023 12:50 PM, Alex Elder wrote:
> 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@...cinc.com>
>> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>
>> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
> 
> I have a minor suggestion.  I think I'd like to look at this
> again, so:
> 
> Acked-by: Alex Elder <elder@...aro.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),            /* ? */
> 

The BIT macro isn't a standard C macro and isn't defined by Linux, so it 
causes compile errors at least for me when I use it in userspace.

>> +};
>> +
>> +/**
>> + * 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.
>