Re: [PATCH v8 06/28] virt: gunyah: Identify hypervisor version

[Elliot Berman <quic_eberman@xxxxxxxxxxx>]

On 1/17/2023 11:21 AM, Alex Elder wrote:
> On 1/10/23 11:56 AM, Elliot Berman wrote:
> > On 1/9/2023 1:34 PM, Alex Elder wrote:
> > > On 12/19/22 4:58 PM, Elliot Berman wrote:
> > > > Export the version of Gunyah which is reported via the hyp_identify
> > > > hypercall. Increments of the major API version indicate possibly
> > > > backwards incompatible changes.
> > > >
> > > > Export the hypervisor identity so that Gunyah drivers can act according
> > > > to the major API version.
> > > >
> > > > Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> > > > ---
> > > >   drivers/virt/Makefile        |  1 +
> > > >   drivers/virt/gunyah/Makefile |  1 +
> > > >   drivers/virt/gunyah/gunyah.c | 46 
> > > > ++++++++++++++++++++++++++++++++++++
> > > >   include/linux/gunyah.h       |  6 +++++
> > > >   4 files changed, 54 insertions(+)
> > > >   create mode 100644 drivers/virt/gunyah/Makefile
> > > >   create mode 100644 drivers/virt/gunyah/gunyah.c
> > > >
> > > > diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> > > > index 093674e05c40..92b7e5311548 100644
> > > > --- a/drivers/virt/Makefile
> > > > +++ b/drivers/virt/Makefile
> > > > @@ -11,3 +11,4 @@ obj-$(CONFIG_NITRO_ENCLAVES)    += nitro_enclaves/
> > > >   obj-$(CONFIG_ACRN_HSM)        += acrn/
> > > >   obj-$(CONFIG_EFI_SECRET)    += coco/efi_secret/
> > > >   obj-$(CONFIG_SEV_GUEST)       += coco/sev-guest/
> > > > +obj-y                += gunyah/
> > > > diff --git a/drivers/virt/gunyah/Makefile 
> > > > b/drivers/virt/gunyah/Makefile
> > > > new file mode 100644
> > > > index 000000000000..2ac4ee64b89d
> > > > --- /dev/null
> > > > +++ b/drivers/virt/gunyah/Makefile
> > > > @@ -0,0 +1 @@
> > > > +obj-$(CONFIG_GUNYAH) += gunyah.o
> > > > diff --git a/drivers/virt/gunyah/gunyah.c 
> > > > b/drivers/virt/gunyah/gunyah.c
> > > > new file mode 100644
> > > > index 000000000000..c34c9046fc08
> > > > --- /dev/null
> > > > +++ b/drivers/virt/gunyah/gunyah.c
> > > > @@ -0,0 +1,46 @@
> > > > +// SPDX-License-Identifier: GPL-2.0-only
> > > > +/*
> > > > + * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights 
> > > > reserved.
> > > > + */
> > > > +
> > > > +#define pr_fmt(fmt) "gunyah: " fmt
> > > > +
> > > > +#include <linux/gunyah.h>
> > > > +#include <linux/init.h>
> > > > +#include <linux/module.h>
> > > > +#include <linux/printk.h>
> > > > +
> > > > +struct gh_hypercall_hyp_identify_resp gunyah_api;
> > > > +EXPORT_SYMBOL_GPL(gunyah_api);
> > > > +
> > > > +static const uint32_t gunyah_known_uuids[][4] = {
> > > > +    {0x19bd54bd, 0x0b37571b, 0x946f609b, 0x54539de6}, /*QC_HYP 
> > > > (Qualcomm's build) */
> > > > +    {0x673d5f14, 0x9265ce36, 0xa4535fdb, 0xc1d58fcd}, /*GUNYAH 
> > > > (open source build) */
> > > > +};
> > > > +
> > > > +static int __init gunyah_init(void)
> > > > +{
> > > > +    u32 uid[4];
> > > > +    int i;
> > > > +
> > > > +    gh_hypercall_get_uid(uid);
> > > > +
> > > > +    for (i = 0; i < ARRAY_SIZE(gunyah_known_uuids); i++)
> > > > +        if (!memcmp(uid, gunyah_known_uuids[i], sizeof(uid)))
> > > > +            break;
> > > > +
> > > > +    if (i == ARRAY_SIZE(gunyah_known_uuids))
> > > > +        return -ENODEV;
> > > > +
> > > > +    gh_hypercall_hyp_identify(&gunyah_api);
> > > > +
> > > > +    pr_info("Running under Gunyah hypervisor %llx/v%u\n",
> > > > +        FIELD_GET(GH_API_INFO_VARIANT_MASK, gunyah_api.api_info),
> > > > +        gh_api_version());
> > > > +
> > > > +    return 0;
> > > > +}
> > > > +arch_initcall(gunyah_init);
> > > > +
> > > > +MODULE_LICENSE("GPL");
> > > > +MODULE_DESCRIPTION("Gunyah Hypervisor Driver");
> > > > diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> > > > index 2765d2b40198..166156f69df9 100644
> > > > --- a/include/linux/gunyah.h
> > > > +++ b/include/linux/gunyah.h
> > > > @@ -92,6 +92,12 @@ struct gh_hypercall_hyp_identify_resp {
> > > >       u64 api_info;
> > > >       u64 flags[3];
> > > >   };
> > > > +extern struct gh_hypercall_hyp_identify_resp gunyah_api;
> > >
> > > Must this global variable be exposed?  Can't you hide it--as
> > > well as its interpretation--inside "gunyah.c"?
> > >  >> +
> > > > +static inline u16 gh_api_version(void)
> > > > +{
> > > > +    return FIELD_GET(GH_API_INFO_API_VERSION_MASK, 
> > > > gunyah_api.api_info);
> > > > +}
> > >
> > > If you don't make the above function inline, can you hide the
> > > definition of gunyah_api?
> >
> > This seems like a good idea to me. I'm thinking to have the following 
> > functions:
> >
> > enum gh_api_feature {
> >      GH_API_FEATURE_DOORBELL,
> >      GH_API_FEATURE_MSGQUEUE,
> >      GH_API_FEATURE_VIC,
> >      GH_API_FEATURE_VPM,
> >      GH_API_FEATURE_VCPU,
> >      GH_API_FEATURE_MEMEXTENT,
> >      GH_API_FEATURE_TRACE_CTRL,
> > };
>
> My point wasn't necessarily to expose all of that.  Already
> "gunyah.h" defines the bit positions in which these things
> are recorded in the identify response.  My main point was
> about (not) exposing that global variable.
>
> I support your suggestion of abstracting the feature
> interface that way, but I suggest waiting until it's
> actually needed before you add it.  I don't see any
> code that uses GH_IDENTIFY_PARTITION_CSPACE (and the
> rest) currently.

Sure, I will do that.
> Oh, and interestingly enough I see GH_API_INFO_BIG_ENDIAN
> defined in the API info...
>
>                      -Alex
>
> > u16 gh_api_version(void);
> > bool gh_api_has_feature(enum gh_api_feature feature);
> >
> > Thanks,
> > Elliot