Re: [XEN PATCH v2 1/5] xen: introduce xen,enhanced dom0less property

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 13 Jan 2022, Bertrand Marquis wrote:
> Hi Stefano,
> 
> > On 13 Jan 2022, at 00:58, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> > 
> > From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> > 
> > 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.)
> 
> You should also say here that you set this option to true in the code for dom0
> and that the option is only for DomUs.

Good point!
 

> > This patch only parses the property. Next patches will make use of it.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> > CC: Julien Grall <julien@xxxxxxx>
> > CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> > CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> 
> With the previous added in commit message:
> Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Thank you!


> Cheers
> Bertrand
> 
> > ---
> > Changes in v2:
> > - rename kinfo.enhanced to kinfo.dom0less_enhanced
> > - set kinfo.dom0less_enhanced to true for dom0
> > - handle -ENODATA in addition to -EILSEQ
> > ---
> > docs/misc/arm/device-tree/booting.txt | 18 ++++++++++++++++++
> > xen/arch/arm/domain_build.c           |  8 ++++++++
> > xen/arch/arm/include/asm/kernel.h     |  3 +++
> > 3 files changed, 29 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..9144d6c0b6 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 *dom0less_enhanced;
> >     int rc;
> >     u64 mem;
> > 
> > @@ -2978,6 +2979,12 @@ static int __init construct_domU(struct domain *d,
> > 
> >     kinfo.vpl011 = dt_property_read_bool(node, "vpl011");
> > 
> > +    rc = dt_property_read_string(node, "xen,enhanced", &dom0less_enhanced);
> > +    if ( rc == -EILSEQ ||
> > +         rc == -ENODATA ||
> > +         (rc == 0 && !strcmp(dom0less_enhanced, "enabled")) )
> > +        kinfo.dom0less_enhanced = true;
> > +
> >     if ( vcpu_create(d, 0) == NULL )
> >         return -ENOMEM;
> > 
> > @@ -3095,6 +3102,7 @@ static int __init construct_dom0(struct domain *d)
> > 
> >     kinfo.unassigned_mem = dom0_mem;
> >     kinfo.d = d;
> > +    kinfo.dom0less_enhanced = true;
> > 
> >     rc = kernel_probe(&kinfo, NULL);
> >     if ( rc < 0 )
> > diff --git a/xen/arch/arm/include/asm/kernel.h 
> > b/xen/arch/arm/include/asm/kernel.h
> > index 874aa108a7..c4dc039b54 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 dom0less_enhanced;
> > +
> >     /* GIC phandle */
> >     uint32_t phandle_gic;
> > 
> > -- 
> > 2.25.1
> > 
>