On 9/18/2025 11:50 AM, Stanislav Kinsburskii wrote:
> On Tue, Sep 16, 2025 at 04:44:20PM -0700, Nuno Das Neves wrote:
>> From: Purna Pavan Chandra Aekkaladevi <paekkalad...@linux.microsoft.com>
>>
>> Some hypervisor APIs are gated by feature bits in the
>> "vmm capabilities" partition property. Store the capabilities on
>> mshv_root module init, using HVCALL_GET_PARTITION_PROPERTY_EX.
>>
>> This is not supported on all hypervisors. In that case, just set the
>> capabilities to 0 and proceed as normal.
>>
>> Signed-off-by: Purna Pavan Chandra Aekkaladevi
>> <paekkalad...@linux.microsoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasne...@linux.microsoft.com>
>> Reviewed-by: Praveen K Paladugu <pra...@linux.microsoft.com>
>> Reviewed-by: Easwar Hariharan <easwar.hariha...@linux.microsoft.com>
>> Reviewed-by: Tianyu Lan <ti...@microsoft.com>
>> ---
>> drivers/hv/mshv_root.h | 1 +
>> drivers/hv/mshv_root_main.c | 22 ++++++++++++++++++++++
>> 2 files changed, 23 insertions(+)
>>
>> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
>> index 4aeb03bea6b6..0cb1e2589fe1 100644
>> --- a/drivers/hv/mshv_root.h
>> +++ b/drivers/hv/mshv_root.h
>> @@ -178,6 +178,7 @@ struct mshv_root {
>> struct hv_synic_pages __percpu *synic_pages;
>> spinlock_t pt_ht_lock;
>> DECLARE_HASHTABLE(pt_htable, MSHV_PARTITIONS_HASH_BITS);
>> + struct hv_partition_property_vmm_capabilities vmm_caps;
>> };
>>
>> /*
>> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
>> index 24df47726363..f7738cefbdf3 100644
>> --- a/drivers/hv/mshv_root_main.c
>> +++ b/drivers/hv/mshv_root_main.c
>> @@ -2201,6 +2201,26 @@ static int __init mshv_root_partition_init(struct
>> device *dev)
>> return err;
>> }
>>
>> +static void mshv_init_vmm_caps(struct device *dev)
>> +{
>> + int ret;
>
> nit: this is void function so ret looks redundant.
>
True, it's not needed.
>> +
>> + memset(&mshv_root.vmm_caps, 0, sizeof(mshv_root.vmm_caps));
>
> Zeroying is redundant as mshv_root is a statci variable.
>
Good point.
>> + ret = hv_call_get_partition_property_ex(HV_PARTITION_ID_SELF,
>> +
>> HV_PARTITION_PROPERTY_VMM_CAPABILITIES,
>> + 0, &mshv_root.vmm_caps,
>
> Also, we align "slow" hypercalls by PAGE_SIZE. Why is it fine to not do
> it here?
>
I guess you're referring to the output argument of the hypercall?
Check the previous patch to see how hv_call_get_partition_property_ex()
is implemented. It uses the per-cpu input/output args as normal, which
are HV_HYP_PAGE_SIZE in size, and page-aligned.
> Thanks,
> Stanislav
>
>> + sizeof(mshv_root.vmm_caps));
>> +
>> + /*
>> + * HVCALL_GET_PARTITION_PROPERTY_EX or
>> HV_PARTITION_PROPERTY_VMM_CAPABILITIES
>> + * may not be supported. Leave them as 0 in that case.
>> + */
>> + if (ret)
>> + dev_warn(dev, "Unable to get VMM capabilities\n");
>> +
>> + dev_dbg(dev, "vmm_caps=0x%llx\n", mshv_root.vmm_caps.as_uint64[0]);
>> +}
>> +
>> static int __init mshv_parent_partition_init(void)
>> {
>> int ret;
>> @@ -2253,6 +2273,8 @@ static int __init mshv_parent_partition_init(void)
>> if (ret)
>> goto remove_cpu_state;
>>
>> + mshv_init_vmm_caps(dev);
>> +
>> ret = mshv_irqfd_wq_init();
>> if (ret)
>> goto exit_partition;
>> --
>> 2.34.1
>>
