Re: [XEN PATCH 4/7] xen: introduce xen,enhanced dom0less property

[Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>]

Hi Stefano,

Stefano Stabellini <sstabellini@kernel.org> writes:

> From: Stefano Stabellini <stefano.stabellini@xilinx.com>
>
> Introduce a new "xen,enhanced" dom0less property to enable/disable PV
> driver interfaces for dom0less guests. Currently only "enabled" and
> "disabled" are supported property values (and empty). Leave the option
> open to implement further possible values in the future (e.g.
> "xenstore" to enable only xenstore.)
>
> This patch only parses the property. Next patches will make use of it.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
> CC: Julien Grall <julien@xen.org>
> CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
> CC: Bertrand Marquis <bertrand.marquis@arm.com>
> ---
>  docs/misc/arm/device-tree/booting.txt | 18 ++++++++++++++++++
>  xen/arch/arm/domain_build.c           |  5 +++++
>  xen/arch/arm/include/asm/kernel.h     |  3 +++
>  3 files changed, 26 insertions(+)
>
> diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt
> index 71895663a4..38c29fb3d8 100644
> --- a/docs/misc/arm/device-tree/booting.txt
> +++ b/docs/misc/arm/device-tree/booting.txt
> @@ -169,6 +169,24 @@ with the following properties:
>      Please note that the SPI used for the virtual pl011 could clash with the
>      physical SPI of a physical device assigned to the guest.
>  
> +- xen,enhanced
> +
> +    A string property. Possible property values are:
> +
> +    - "enabled" (or missing property value)
> +    Xen PV interfaces, including grant-table and xenstore, will be
> +    enabled for the VM.
> +
> +    - "disabled"
> +    Xen PV interfaces are disabled.
> +
> +    If the xen,enhanced property is present with no value, it defaults
> +    to "enabled". If the xen,enhanced property is not present, PV
> +    interfaces are disabled.
> +
> +    In the future other possible property values might be added to
> +    enable only selected interfaces.
> +
>  - nr_spis
>  
>      Optional. A 32-bit integer specifying the number of SPIs (Shared
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 6931c022a2..96a94fa434 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -2963,6 +2963,7 @@ static int __init construct_domU(struct domain *d,
>                                   const struct dt_device_node *node)
>  {
>      struct kernel_info kinfo = {};
> +    const char *enhanced;
>      int rc;
>      u64 mem;
>  
> @@ -2978,6 +2979,10 @@ static int __init construct_domU(struct domain *d,
>  
>      kinfo.vpl011 = dt_property_read_bool(node, "vpl011");
>  
> +    rc = dt_property_read_string(node, "xen,enhanced", &enhanced);
> +    if ( rc == -EILSEQ || (rc == 0 && !strcmp(enhanced, "enabled")) )

Are you sure you need to check for -EILSEQ?

From documentation for dt_property_read_string:

 * Returns 0 on
 * success, -EINVAL if the property does not exist, -ENODATA if property
 * doest not have value, and -EILSEQ if the string is not
 * null-terminated with the length of the property data.


So, for me it looks like you need to check for -ENODATA.

> +        kinfo.enhanced = true;
> +
>      if ( vcpu_create(d, 0) == NULL )
>          return -ENOMEM;
>  
> diff --git a/xen/arch/arm/include/asm/kernel.h b/xen/arch/arm/include/asm/kernel.h
> index 874aa108a7..3275f7fbca 100644
> --- a/xen/arch/arm/include/asm/kernel.h
> +++ b/xen/arch/arm/include/asm/kernel.h
> @@ -36,6 +36,9 @@ struct kernel_info {
>      /* Enable pl011 emulation */
>      bool vpl011;
>  
> +    /* Enable PV drivers */
> +    bool enhanced;

Maybe dom0less_enhanced will be better name?
Or what about dom0? Should it have this option enabled?

> +
>      /* GIC phandle */
>      uint32_t phandle_gic;


-- 
Volodymyr Babchuk at EPAM