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

[Elliot Berman]

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,
};

u16 gh_api_version(void);
bool gh_api_has_feature(enum gh_api_feature feature);

Thanks,
Elliot