Re: [PATCH 6/6] mshv: Introduce new hypercall to map stats page for L1VH partitions

[Nuno Das Neves <nunodasneves@linux.microsoft.com>]

On 9/5/2025 12:50 PM, Easwar Hariharan wrote:
> On 8/28/2025 5:43 PM, Nuno Das Neves wrote:
>> From: Jinank Jain <jinankjain@linux.microsoft.com>
>>
>> Introduce HVCALL_MAP_STATS_PAGE2 which provides a map location (GPFN)
>> to map the stats to. This hypercall is required for L1VH partitions,
>> depending on the hypervisor version. This uses the same check as the
>> state page map location; mshv_use_overlay_gpfn().
>>
>> Add mshv_map_vp_state_page() helpers to use this new hypercall or the
>> old one depending on availability.
>>
>> For unmapping, the original HVCALL_UNMAP_STATS_PAGE works for both
>> cases.
>>
>> Signed-off-by: Jinank Jain <jinankjain@linux.microsoft.com>
>> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
>> ---
>>  drivers/hv/mshv_root.h         | 10 ++--
>>  drivers/hv/mshv_root_hv_call.c | 92 ++++++++++++++++++++++++++++++++--
>>  drivers/hv/mshv_root_main.c    | 25 +++++----
>>  include/hyperv/hvgdk_mini.h    |  1 +
>>  include/hyperv/hvhdk_mini.h    |  7 +++
>>  5 files changed, 115 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
>> index d7c9520ef788..d16a020ae0ee 100644
>> --- a/drivers/hv/mshv_root.h
>> +++ b/drivers/hv/mshv_root.h
>> @@ -297,11 +297,11 @@ int hv_call_connect_port(u64 port_partition_id, union hv_port_id port_id,
>>  int hv_call_disconnect_port(u64 connection_partition_id,
>>  			    union hv_connection_id connection_id);
>>  int hv_call_notify_port_ring_empty(u32 sint_index);
>> -int hv_call_map_stat_page(enum hv_stats_object_type type,
>> -			  const union hv_stats_object_identity *identity,
>> -			  void **addr);
>> -int hv_call_unmap_stat_page(enum hv_stats_object_type type,
>> -			    const union hv_stats_object_identity *identity);
>> +int hv_map_stats_page(enum hv_stats_object_type type,
>> +		      const union hv_stats_object_identity *identity,
>> +		      void **addr);
>> +int hv_unmap_stats_page(enum hv_stats_object_type type, void *page_addr,
>> +			const union hv_stats_object_identity *identity);
>>  int hv_call_modify_spa_host_access(u64 partition_id, struct page **pages,
>>  				   u64 page_struct_count, u32 host_access,
>>  				   u32 flags, u8 acquire);
>> diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
>> index 1882cc90f2f5..44013751cfc1 100644
>> --- a/drivers/hv/mshv_root_hv_call.c
>> +++ b/drivers/hv/mshv_root_hv_call.c
>> @@ -804,6 +804,45 @@ hv_call_notify_port_ring_empty(u32 sint_index)
>>  	return hv_result_to_errno(status);
>>  }
>>  
>> +static int
>> +hv_call_map_stats_page2(enum hv_stats_object_type type,
> 
> Again, one line please. Also below.
> 
Ack

>> +			const union hv_stats_object_identity *identity,
>> +			u64 map_location)
>> +{
>> +	unsigned long flags;
>> +	struct hv_input_map_stats_page2 *input;
>> +	u64 status;
>> +	int ret;
>> +
>> +	if (!map_location || !mshv_use_overlay_gpfn())
>> +		return -EINVAL;
>> +
>> +	do {
>> +		local_irq_save(flags);
>> +		input = *this_cpu_ptr(hyperv_pcpu_input_arg);
>> +
>> +		memset(input, 0, sizeof(*input));
>> +		input->type = type;
>> +		input->identity = *identity;
>> +		input->map_location = map_location;
>> +
>> +		status = hv_do_hypercall(HVCALL_MAP_STATS_PAGE2, input, NULL);
>> +
>> +		local_irq_restore(flags);
>> +		if (hv_result(status) != HV_STATUS_INSUFFICIENT_MEMORY) {
>> +			if (hv_result_success(status))
>> +				break;
>> +			hv_status_debug(status, "\n");
>> +			return hv_result_to_errno(status);
>> +		}
>> +
>> +		ret = hv_call_deposit_pages(NUMA_NO_NODE,
>> +					    hv_current_partition_id, 1);
>> +	} while (!ret);
>> +
>> +	return ret;
>> +}
>> +
>>  static int
>>  hv_stats_get_area_type(enum hv_stats_object_type type,
>>  		       const union hv_stats_object_identity *identity)
>> @@ -822,9 +861,10 @@ hv_stats_get_area_type(enum hv_stats_object_type type,
>>  	return -EINVAL;
>>  }
>>  
>> -int hv_call_map_stat_page(enum hv_stats_object_type type,
>> -			  const union hv_stats_object_identity *identity,
>> -			  void **addr)
>> +static int
>> +hv_call_map_stats_page(enum hv_stats_object_type type,
>> +		       const union hv_stats_object_identity *identity,
>> +		       void **addr)
> 
> ...
> 
ack

>>  {
>>  	unsigned long flags;
>>  	struct hv_input_map_stats_page *input;
>> @@ -880,8 +920,37 @@ int hv_call_map_stat_page(enum hv_stats_object_type type,
>>  	return ret;
>>  }
>>  
>> -int hv_call_unmap_stat_page(enum hv_stats_object_type type,
>> -			    const union hv_stats_object_identity *identity)
>> +int hv_map_stats_page(enum hv_stats_object_type type,
>> +		      const union hv_stats_object_identity *identity,
>> +		      void **addr)
>> +{
>> +	int ret;
>> +	struct page *allocated_page = NULL;
>> +
>> +	if (!addr)
>> +		return -EINVAL;
>> +
>> +	if (mshv_use_overlay_gpfn()) {
>> +		allocated_page = alloc_page(GFP_KERNEL);
>> +		if (!allocated_page)
>> +			return -ENOMEM;
>> +
>> +		ret = hv_call_map_stats_page2(type, identity,
>> +					      page_to_pfn(allocated_page));
>> +		*addr = page_address(allocated_page);
>> +	} else {
>> +		ret = hv_call_map_stats_page(type, identity, addr);
>> +	}
>> +
>> +	if (ret && allocated_page)
>> +		__free_page(allocated_page);
>> +
>> +	return ret;
>> +}
>> +
>> +static int
>> +hv_call_unmap_stats_page(enum hv_stats_object_type type,
> 
> ...
> 
ack

>> +			 const union hv_stats_object_identity *identity)
>>  {
>>  	unsigned long flags;
>>  	struct hv_input_unmap_stats_page *input;
>> @@ -900,6 +969,19 @@ int hv_call_unmap_stat_page(enum hv_stats_object_type type,
>>  	return hv_result_to_errno(status);
>>  }
>>  
>> +int hv_unmap_stats_page(enum hv_stats_object_type type, void *page_addr,
>> +			const union hv_stats_object_identity *identity)
>> +{
>> +	int ret;
>> +
>> +	ret = hv_call_unmap_stats_page(type, identity);
>> +
>> +	if (mshv_use_overlay_gpfn() && page_addr)
>> +		__free_page(virt_to_page(page_addr));
>> +
>> +	return ret;
>> +}
>> +
>>  int hv_call_modify_spa_host_access(u64 partition_id, struct page **pages,
>>  				   u64 page_struct_count, u32 host_access,
>>  				   u32 flags, u8 acquire)
>> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
>> index f91880cc9e29..1699423cc524 100644
>> --- a/drivers/hv/mshv_root_main.c
>> +++ b/drivers/hv/mshv_root_main.c
>> @@ -894,7 +894,8 @@ mshv_vp_release(struct inode *inode, struct file *filp)
>>  	return 0;
>>  }
>>  
>> -static void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index)
>> +static void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index,
>> +				void *stats_pages[])
>>  {
>>  	union hv_stats_object_identity identity = {
>>  		.vp.partition_id = partition_id,
>> @@ -902,10 +903,13 @@ static void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index)
>>  	};
>>  
>>  	identity.vp.stats_area_type = HV_STATS_AREA_SELF;
>> -	hv_call_unmap_stat_page(HV_STATS_OBJECT_VP, &identity);
>> +	hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
>> +
>> +	if (stats_pages[HV_STATS_AREA_PARENT] == stats_pages[HV_STATS_AREA_SELF])
>> +		return;
>>  
>>  	identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
>> -	hv_call_unmap_stat_page(HV_STATS_OBJECT_VP, &identity);
>> +	hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
>>  }
>>  
>>  static int mshv_vp_stats_map(u64 partition_id, u32 vp_index,
>> @@ -918,14 +922,14 @@ static int mshv_vp_stats_map(u64 partition_id, u32 vp_index,
>>  	int err;
>>  
>>  	identity.vp.stats_area_type = HV_STATS_AREA_SELF;
>> -	err = hv_call_map_stat_page(HV_STATS_OBJECT_VP, &identity,
>> -				    &stats_pages[HV_STATS_AREA_SELF]);
>> +	err = hv_map_stats_page(HV_STATS_OBJECT_VP, &identity,
>> +				&stats_pages[HV_STATS_AREA_SELF]);
> 
> Shouldn't this be in the previous patch where the other hv_call_map_stat_page() calls were
> converted, same below?
> 
The previous patch converts hv_call_(un)map_vp_state_page to hv_(un)map_vp_state_page, i.e.
"state" not "stats".

>>  	if (err)
>>  		return err;
>>  
>>  	identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
>> -	err = hv_call_map_stat_page(HV_STATS_OBJECT_VP, &identity,
>> -				    &stats_pages[HV_STATS_AREA_PARENT]);
>> +	err = hv_map_stats_page(HV_STATS_OBJECT_VP, &identity,
>> +				&stats_pages[HV_STATS_AREA_PARENT]);
> 
> ...
> 
>>  	if (err)
>>  		goto unmap_self;
>>  
>> @@ -936,7 +940,7 @@ static int mshv_vp_stats_map(u64 partition_id, u32 vp_index,
>>  
>>  unmap_self:
>>  	identity.vp.stats_area_type = HV_STATS_AREA_SELF;
>> -	hv_call_unmap_stat_page(HV_STATS_OBJECT_VP, &identity);
>> +	hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
>>  	return err;
>>  }
>>
> 
> <snip>