From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@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 <paekkaladevi@linux.microsoft.com>
Signed-off-by: Nuno Das Neves <nunodasneves@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;
+ }
+
ret = mshv_irqfd_wq_init();
if (ret)
goto exit_partition;
--
2.34.1On Fri, Aug 29, 2025 at 8:44 AM Nuno Das Neves
<nunodasneves@linux.microsoft.com> wrote:
>
> From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@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 <paekkaladevi@linux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> ---
Reviewed-by: Tianyu Lan <tiala@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;
> + }
> +
> ret = mshv_irqfd_wq_init();
> if (ret)
> goto exit_partition;
> --
> 2.34.1
>
>
--
Thanks
Tianyu Lan
On 8/28/2025 5:43 PM, Nuno Das Neves wrote: > From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@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 <paekkaladevi@linux.microsoft.com> > Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com> > --- > drivers/hv/mshv_root.h | 1 + > drivers/hv/mshv_root_main.c | 28 ++++++++++++++++++++++++++++ > 2 files changed, 29 insertions(+) Looks good to me. Reviewed-by: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>
On Thu, Aug 28, 2025 at 05:43:48PM -0700, Nuno Das Neves wrote:
> From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@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 <paekkaladevi@linux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@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
>
On 9/5/2025 12:03 PM, Anirudh Rayabharam wrote:
> On Thu, Aug 28, 2025 at 05:43:48PM -0700, Nuno Das Neves wrote:
>> From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@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 <paekkaladevi@linux.microsoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasneves@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.
>
I agree. It can continue with vmm_caps set to zero, and print an error.
The check for -EIO is meant to achieve something similar but it's kind of
unreliable since so many HV_STATUS's map to EIO. So this idea is better,
thanks.
Nuno
> Thanks,
> Anirudh.
>
>> + }
>> +
>> ret = mshv_irqfd_wq_init();
>> if (ret)
>> goto exit_partition;
>> --
>> 2.34.1
>>
On 8/28/2025 7:43 PM, Nuno Das Neves wrote:
> From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@linux.microsoft.com>
>
> Some newer hypervisor APIs are gated by feature bits in the so-called
> "vmm capabilities" partition property. Store the capabilities on
nit: s/xx/Some hypervisor APIs are gated by feature bits exposed in
"vmm capabilities" partition property./g> mshv_root module init, using
HVCALL_GET_PARTITION_PROPERTY_EX.
>
> Signed-off-by: Purna Pavan Chandra Aekkaladevi <paekkaladevi@linux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@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;
> + }
> +
> ret = mshv_irqfd_wq_init();
> if (ret)
> goto exit_partition;
Reviewed-by: Praveen K Paladugu <prapal@linux.microsoft.com>
--
Regards,
Praveen K Paladugu
On 9/5/2025 8:43 AM, Praveen K Paladugu wrote:
>
>
> On 8/28/2025 7:43 PM, Nuno Das Neves wrote:
>> From: Purna Pavan Chandra Aekkaladevi <paekkaladevi@linux.microsoft.com>
>>
>> Some newer hypervisor APIs are gated by feature bits in the so-called
>> "vmm capabilities" partition property. Store the capabilities on
> nit: s/xx/Some hypervisor APIs are gated by feature bits exposed in
> "vmm capabilities" partition property./g
Thanks, I'll update it for v2
Nuno
>> mshv_root module init, using HVCALL_GET_PARTITION_PROPERTY_EX.
>>>> Signed-off-by: Purna Pavan Chandra Aekkaladevi <paekkaladevi@linux.microsoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasneves@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;
>> + }
>> +
>> ret = mshv_irqfd_wq_init();
>> if (ret)
>> goto exit_partition;
>
> Reviewed-by: Praveen K Paladugu <prapal@linux.microsoft.com>
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