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

[Elliot Berman <quic_eberman@quicinc.com>]

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@quicinc.com>
>>>> ---
>>>>   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
>