linux-kernel - Re: [PATCH v9 24/27] virt: gunyah: Add proxy-scheduled vCPUs

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Message-ID: <8b03eafd-8d8e-6e80-2b88-0e186f3ab392@linaro.org>
Date:   Tue, 7 Feb 2023 14:43:13 +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>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
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>,
        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 24/27] virt: gunyah: Add proxy-scheduled vCPUs



On 20/01/2023 22:46, Elliot Berman wrote:
> Gunyah allows host virtual machines to schedule guest virtual machines
> and handle their MMIO accesses. vCPUs are presented to the host as a
> Gunyah resource and represented to userspace as a Gunyah VM function.
> 
> Creating the vcpu VM function will create a file descriptor that:
>   - can run an ioctl: GH_VCPU_RUN to schedule the guest vCPU until the
>     next interrupt occurs on the host or when the guest vCPU can no
>     longer be run.
>   - can be mmap'd to share a gh_vcpu_run structure which can look up the
>     reason why GH_VCPU_RUN returned and provide return values for MMIO
>     access.
> 
> 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 |  30 +-
>   arch/arm64/gunyah/gunyah_hypercall.c     |  28 ++
>   drivers/virt/gunyah/Kconfig              |  11 +
>   drivers/virt/gunyah/Makefile             |   2 +
>   drivers/virt/gunyah/gunyah_vcpu.c        | 358 +++++++++++++++++++++++
>   drivers/virt/gunyah/vm_mgr.c             |  25 ++
>   drivers/virt/gunyah/vm_mgr.h             |   1 +
>   include/linux/gunyah.h                   |   7 +
>   include/uapi/linux/gunyah.h              |  30 ++
>   9 files changed, 490 insertions(+), 2 deletions(-)
>   create mode 100644 drivers/virt/gunyah/gunyah_vcpu.c
> 
...


> diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
> index ec8da6fde045..b4afb11f538a 100644
> --- a/include/uapi/linux/gunyah.h
> +++ b/include/uapi/linux/gunyah.h
> @@ -53,9 +53,14 @@ struct gh_vm_dtb_config {
>   #define GUNYAH_FUNCTION_NAME_SIZE		32
>   #define GUNYAH_FUNCTION_MAX_ARG_SIZE		1024
>   
> +struct gh_fn_vcpu_arg {
> +	__u32 vcpu_id;
> +};
> +
>   struct gh_vm_function {
>   	char name[GUNYAH_FUNCTION_NAME_SIZE];
>   	union {
> +		struct gh_device_vcpu_arg vcpu;
>   		char data[GUNYAH_FUNCTION_MAX_ARG_SIZE];
>   	};
>   };
> @@ -63,4 +68,29 @@ struct gh_vm_function {
>   #define GH_VM_ADD_FUNCTION	_IOW(GH_IOCTL_TYPE, 0x4, struct gh_vm_function)
>   #define GH_VM_REMOVE_FUNCTION	_IOW(GH_IOCTL_TYPE, 0x7, struct gh_vm_function)
>   
> +/* for GH_VCPU_RUN, returned by mmap(vcpu_fd, offset=0) */
> +struct gh_vcpu_run {
this looks unused, I dont see any reference to this.

> +	/* in */
> +	__u8 immediate_exit;
> +	__u8 padding1[7];
> +
> +	/* out */
> +#define GH_VM_EXIT_UNKNOWN            0
> +#define GH_VM_EXIT_MMIO               1
> +	__u32 exit_reason;

If this is ment to go in any of the ioctl arguments then this suffers 
same issue of padding.

> +
> +	union {
> +		/* GH_VM_EXIT_MMIO */
> +		struct {
> +			__u64 phys_addr;
> +			__u8  data[8];
> +			__u32 len;
> +			__u8  is_write;
> +		} mmio;
> +	};
> +};
> +
> +#define GH_VCPU_RUN		_IO(GH_IOCTL_TYPE, 0x5)
> +#define GH_VCPU_MMAP_SIZE	_IO(GH_IOCTL_TYPE, 0x6)
> +
>   #endif