On Thu, Aug 28, 2025 at 05:43:48PM -0700, Nuno Das Neves wrote:
> From: Purna Pavan Chandra Aekkaladevi <paekkalad...@linux.microsoft.com>
>
> Some newer hypervisor APIs are gated by feature bits in the so-called
> "vmm capabilities" partition property. Store the capabilities on
> mshv_root module init, using HVCALL_GET_PARTITION_PROPERTY_EX.
>
> Signed-off-by: Purna Pavan Chandra Aekkaladevi
> <paekkalad...@linux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasne...@linux.microsoft.com>
> ---
> drivers/hv/mshv_root.h | 1 +
> drivers/hv/mshv_root_main.c | 28 ++++++++++++++++++++++++++++
> 2 files changed, 29 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 56ababab57ce..29f61ecc9771 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -2327,6 +2327,28 @@ static int __init mshv_root_partition_init(struct
> device *dev)
> return err;
> }
>
> +static int mshv_init_vmm_caps(struct device *dev)
> +{
> + int ret;
> +
> + memset(&mshv_root.vmm_caps, 0, sizeof(mshv_root.vmm_caps));
> + ret = hv_call_get_partition_property_ex(HV_PARTITION_ID_SELF,
> +
> HV_PARTITION_PROPERTY_VMM_CAPABILITIES,
> + 0, &mshv_root.vmm_caps,
> + sizeof(mshv_root.vmm_caps));
> +
> + /*
> + * HV_PARTITION_PROPERTY_VMM_CAPABILITIES is not supported in
> + * older hyperv. Ignore the -EIO error code.
> + */
> + if (ret && ret != -EIO)
> + return ret;
> +
> + dev_dbg(dev, "vmm_caps=0x%llx\n", mshv_root.vmm_caps.as_uint64[0]);
> +
> + return 0;
> +}
> +
> static int __init mshv_parent_partition_init(void)
> {
> int ret;
> @@ -2377,6 +2399,12 @@ static int __init mshv_parent_partition_init(void)
> if (ret)
> goto remove_cpu_state;
>
> + ret = mshv_init_vmm_caps(dev);
> + if (ret) {
> + dev_err(dev, "Failed to get VMM capabilities\n");
> + goto exit_partition;
Should this really be treated as a failure here? We could still offer
/dev/mshv albeit with potentially limited capabilities.
Thanks,
Anirudh.
> + }
> +
> ret = mshv_irqfd_wq_init();
> if (ret)
> goto exit_partition;
> --
> 2.34.1
>
