[Patch v2 1/4] Drivers: hv: Allocate interrupt and monitor pages aligned to system page boundary

[Patch v2 1/4] Drivers: hv: Allocate interrupt and monitor pages aligned to system page boundary

[longli]

From: Long Li <longli@microsoft.com>

There are use cases that interrupt and monitor pages are mapped to
user-mode through UIO, they need to be system page aligned. Some Hyper-V
allocation APIs introduced earlier broke those requirements.

Fix those APIs by always allocating Hyper-V page at system page boundaries.

Cc: stable@vger.kernel.org
Fixes: ca48739e59df ("Drivers: hv: vmbus: Move Hyper-V page allocator to arch neutral code")
Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/hv/hv_common.c | 35 ++++++++++-------------------------
 1 file changed, 10 insertions(+), 25 deletions(-)

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index a7d7494feaca..297ccd7d4997 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -106,41 +106,26 @@ void __init hv_common_free(void)
 }
 
 /*
- * Functions for allocating and freeing memory with size and
- * alignment HV_HYP_PAGE_SIZE. These functions are needed because
- * the guest page size may not be the same as the Hyper-V page
- * size. We depend upon kmalloc() aligning power-of-two size
- * allocations to the allocation size boundary, so that the
- * allocated memory appears to Hyper-V as a page of the size
- * it expects.
+ * A Hyper-V page can be used by UIO for mapping to user-space, it should
+ * always be allocated on system page boundaries.
  */
-
 void *hv_alloc_hyperv_page(void)
 {
-	BUILD_BUG_ON(PAGE_SIZE <  HV_HYP_PAGE_SIZE);
-
-	if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
-		return (void *)__get_free_page(GFP_KERNEL);
-	else
-		return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
+	return (void *)__get_free_page(GFP_KERNEL);
 }
 EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
 
 void *hv_alloc_hyperv_zeroed_page(void)
 {
-	if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
-		return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
-	else
-		return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
+	return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
 }
 EXPORT_SYMBOL_GPL(hv_alloc_hyperv_zeroed_page);
 
 void hv_free_hyperv_page(void *addr)
 {
-	if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
-		free_page((unsigned long)addr);
-	else
-		kfree(addr);
+	free_page((unsigned long)addr);
 }
 EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
 
@@ -272,7 +257,7 @@ static void hv_kmsg_dump_unregister(void)
 	atomic_notifier_chain_unregister(&panic_notifier_list,
 					 &hyperv_panic_report_block);
 
-	hv_free_hyperv_page(hv_panic_page);
+	kfree(hv_panic_page);
 	hv_panic_page = NULL;
 }
 
@@ -280,7 +265,7 @@ static void hv_kmsg_dump_register(void)
 {
 	int ret;
 
-	hv_panic_page = hv_alloc_hyperv_zeroed_page();
+	hv_panic_page = kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
 	if (!hv_panic_page) {
 		pr_err("Hyper-V: panic message page memory allocation failed\n");
 		return;
@@ -289,7 +274,7 @@ static void hv_kmsg_dump_register(void)
 	ret = kmsg_dump_register(&hv_kmsg_dumper);
 	if (ret) {
 		pr_err("Hyper-V: kmsg dump register error 0x%x\n", ret);
-		hv_free_hyperv_page(hv_panic_page);
+		kfree(hv_panic_page);
 		hv_panic_page = NULL;
 	}
 }
-- 
2.34.1

RE: [Patch v2 1/4] Drivers: hv: Allocate interrupt and monitor pages aligned to system page boundary

[Michael Kelley]

From: longli@linuxonhyperv.com <longli@linuxonhyperv.com> Sent: Wednesday, April 30, 2025 3:06 PM
> 
> There are use cases that interrupt and monitor pages are mapped to
> user-mode through UIO, they need to be system page aligned. Some Hyper-V

s/UIO, they/UIO, so they/

> allocation APIs introduced earlier broke those requirements.
> 
> Fix those APIs by always allocating Hyper-V page at system page boundaries.

This patch modifies hv_alloc_hyperv_page() and friends. Then Patch 4 of the
series deletes them, including the modifications. It would be less code motion
to do the first part of Patch 4 (i.e., the use of __get_free_page directly in
connection.c) here in Patch 1, and leave hv_alloc_hyperv_page() and friends
unmodified. Continue to make the change to hv_kmsg_dump_register() here
in Patch 1 as well.

Then have Patch 2 simply delete hv_alloc_hyperv_page() and friends
because they are no longer used. The modifications to hv_alloc_hyperv_page()
and friends would not be needed.

Patch 3 and 4 would be the additional changes in uio_hv_generic.c.

Michael

> 
> Cc: stable@vger.kernel.org
> Fixes: ca48739e59df ("Drivers: hv: vmbus: Move Hyper-V page allocator to arch neutral code")
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  drivers/hv/hv_common.c | 35 ++++++++++-------------------------
>  1 file changed, 10 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index a7d7494feaca..297ccd7d4997 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -106,41 +106,26 @@ void __init hv_common_free(void)
>  }
> 
>  /*
> - * Functions for allocating and freeing memory with size and
> - * alignment HV_HYP_PAGE_SIZE. These functions are needed because
> - * the guest page size may not be the same as the Hyper-V page
> - * size. We depend upon kmalloc() aligning power-of-two size
> - * allocations to the allocation size boundary, so that the
> - * allocated memory appears to Hyper-V as a page of the size
> - * it expects.
> + * A Hyper-V page can be used by UIO for mapping to user-space, it should
> + * always be allocated on system page boundaries.
>   */
> -
>  void *hv_alloc_hyperv_page(void)
>  {
> -	BUILD_BUG_ON(PAGE_SIZE <  HV_HYP_PAGE_SIZE);
> -
> -	if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
> -		return (void *)__get_free_page(GFP_KERNEL);
> -	else
> -		return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
> +	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
> +	return (void *)__get_free_page(GFP_KERNEL);
>  }
>  EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
> 
>  void *hv_alloc_hyperv_zeroed_page(void)
>  {
> -	if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
> -		return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
> -	else
> -		return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
> +	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
> +	return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
>  }
>  EXPORT_SYMBOL_GPL(hv_alloc_hyperv_zeroed_page);
> 
>  void hv_free_hyperv_page(void *addr)
>  {
> -	if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
> -		free_page((unsigned long)addr);
> -	else
> -		kfree(addr);
> +	free_page((unsigned long)addr);
>  }
>  EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
> 
> @@ -272,7 +257,7 @@ static void hv_kmsg_dump_unregister(void)
>  	atomic_notifier_chain_unregister(&panic_notifier_list,
>  					 &hyperv_panic_report_block);
> 
> -	hv_free_hyperv_page(hv_panic_page);
> +	kfree(hv_panic_page);
>  	hv_panic_page = NULL;
>  }
> 
> @@ -280,7 +265,7 @@ static void hv_kmsg_dump_register(void)
>  {
>  	int ret;
> 
> -	hv_panic_page = hv_alloc_hyperv_zeroed_page();
> +	hv_panic_page = kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
>  	if (!hv_panic_page) {
>  		pr_err("Hyper-V: panic message page memory allocation failed\n");
>  		return;
> @@ -289,7 +274,7 @@ static void hv_kmsg_dump_register(void)
>  	ret = kmsg_dump_register(&hv_kmsg_dumper);
>  	if (ret) {
>  		pr_err("Hyper-V: kmsg dump register error 0x%x\n", ret);
> -		hv_free_hyperv_page(hv_panic_page);
> +		kfree(hv_panic_page);
>  		hv_panic_page = NULL;
>  	}
>  }
> --
> 2.34.1
> 

RE: [Patch v2 1/4] Drivers: hv: Allocate interrupt and monitor pages aligned to system page boundary

[Long Li]

> -----Original Message-----
> From: Michael Kelley <mhklinux@outlook.com>
> Sent: Wednesday, April 30, 2025 6:56 PM
> To: longli@linuxonhyperv.com; KY Srinivasan <kys@microsoft.com>; Haiyang
> Zhang <haiyangz@microsoft.com>; Wei Liu <wei.liu@kernel.org>; Dexuan Cui
> <decui@microsoft.com>; Greg Kroah-Hartman
> <gregkh@linuxfoundation.org>; linux-hyperv@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Cc: Long Li <longli@microsoft.com>; stable@vger.kernel.org
> Subject: [EXTERNAL] RE: [Patch v2 1/4] Drivers: hv: Allocate interrupt and
> monitor pages aligned to system page boundary
> 
> From: longli@linuxonhyperv.com <longli@linuxonhyperv.com> Sent:
> Wednesday, April 30, 2025 3:06 PM
> >
> > There are use cases that interrupt and monitor pages are mapped to
> > user-mode through UIO, they need to be system page aligned. Some
> > Hyper-V
> 
> s/UIO, they/UIO, so they/
> 
> > allocation APIs introduced earlier broke those requirements.
> >
> > Fix those APIs by always allocating Hyper-V page at system page boundaries.
> 
> This patch modifies hv_alloc_hyperv_page() and friends. Then Patch 4 of the
> series deletes them, including the modifications. It would be less code motion
> to do the first part of Patch 4 (i.e., the use of __get_free_page directly in
> connection.c) here in Patch 1, and leave hv_alloc_hyperv_page() and friends
> unmodified. Continue to make the change to hv_kmsg_dump_register() here
> in Patch 1 as well.
> 
> Then have Patch 2 simply delete hv_alloc_hyperv_page() and friends because
> they are no longer used. The modifications to hv_alloc_hyperv_page() and
> friends would not be needed.
> 
> Patch 3 and 4 would be the additional changes in uio_hv_generic.c.
> 
> Michael

I have sent v3 of the patch series.

Long

[Patch v2 2/4] uio_hv_generic: Use correct size for interrupt and monitor pages

[longli]

From: Long Li <longli@microsoft.com>

Interrupt and monitor pages should be in Hyper-V page size (4k bytes).
This can be different to the system page size.

This size is read and used by the user-mode program to determine the
mapped data region. An example of such user-mode program is the VMBUS
driver in DPDK.

Cc: stable@vger.kernel.org
Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus")
Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/uio/uio_hv_generic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 1b19b5647495..08385b04c4ab 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -287,13 +287,13 @@ hv_uio_probe(struct hv_device *dev,
 	pdata->info.mem[INT_PAGE_MAP].name = "int_page";
 	pdata->info.mem[INT_PAGE_MAP].addr
 		= (uintptr_t)vmbus_connection.int_page;
-	pdata->info.mem[INT_PAGE_MAP].size = PAGE_SIZE;
+	pdata->info.mem[INT_PAGE_MAP].size = HV_HYP_PAGE_SIZE;
 	pdata->info.mem[INT_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
 
 	pdata->info.mem[MON_PAGE_MAP].name = "monitor_page";
 	pdata->info.mem[MON_PAGE_MAP].addr
 		= (uintptr_t)vmbus_connection.monitor_pages[1];
-	pdata->info.mem[MON_PAGE_MAP].size = PAGE_SIZE;
+	pdata->info.mem[MON_PAGE_MAP].size = HV_HYP_PAGE_SIZE;
 	pdata->info.mem[MON_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
 
 	if (channel->device_id == HV_NIC) {
-- 
2.34.1

RE: [Patch v2 2/4] uio_hv_generic: Use correct size for interrupt and monitor pages

[Michael Kelley]

From: longli@linuxonhyperv.com <longli@linuxonhyperv.com> Sent: Wednesday, April 30, 2025 3:06 PM
> 
> Interrupt and monitor pages should be in Hyper-V page size (4k bytes).
> This can be different to the system page size.

s/different to/different from/

> 
> This size is read and used by the user-mode program to determine the
> mapped data region. An example of such user-mode program is the VMBUS

s/VMBUS/VMBus/

> driver in DPDK.
> 
> Cc: stable@vger.kernel.org
> Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus")
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  drivers/uio/uio_hv_generic.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index 1b19b5647495..08385b04c4ab 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -287,13 +287,13 @@ hv_uio_probe(struct hv_device *dev,
>  	pdata->info.mem[INT_PAGE_MAP].name = "int_page";
>  	pdata->info.mem[INT_PAGE_MAP].addr
>  		= (uintptr_t)vmbus_connection.int_page;
> -	pdata->info.mem[INT_PAGE_MAP].size = PAGE_SIZE;
> +	pdata->info.mem[INT_PAGE_MAP].size = HV_HYP_PAGE_SIZE;
>  	pdata->info.mem[INT_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
> 
>  	pdata->info.mem[MON_PAGE_MAP].name = "monitor_page";
>  	pdata->info.mem[MON_PAGE_MAP].addr
>  		= (uintptr_t)vmbus_connection.monitor_pages[1];
> -	pdata->info.mem[MON_PAGE_MAP].size = PAGE_SIZE;
> +	pdata->info.mem[MON_PAGE_MAP].size = HV_HYP_PAGE_SIZE;
>  	pdata->info.mem[MON_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
> 
>  	if (channel->device_id == HV_NIC) {
> --
> 2.34.1
> 

[Patch v2 3/4] uio_hv_generic: Adjust ring size according to system page alignment

[longli]

From: Long Li <longli@microsoft.com>

Following the ring header, the ring data should align to system page
boundary. Adjust the size if necessary.

Cc: stable@vger.kernel.org
Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus")
Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/uio/uio_hv_generic.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 08385b04c4ab..dfc5f0e1a254 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -256,6 +256,12 @@ hv_uio_probe(struct hv_device *dev,
 	if (!ring_size)
 		ring_size = SZ_2M;
 
+	/*
+	 * Adjust ring size if necessary to have the ring data region page
+	 * aligned
+	 */
+	ring_size = VMBUS_RING_SIZE(ring_size);
+
 	pdata = devm_kzalloc(&dev->device, sizeof(*pdata), GFP_KERNEL);
 	if (!pdata)
 		return -ENOMEM;
-- 
2.34.1

RE: [Patch v2 3/4] uio_hv_generic: Adjust ring size according to system page alignment

[Michael Kelley]

From: longli@linuxonhyperv.com <longli@linuxonhyperv.com> Sent: Wednesday, April 30, 2025 3:06 PM
> 
> Following the ring header, the ring data should align to system page
> boundary. Adjust the size if necessary.
> 
> Cc: stable@vger.kernel.org
> Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus")
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  drivers/uio/uio_hv_generic.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index 08385b04c4ab..dfc5f0e1a254 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -256,6 +256,12 @@ hv_uio_probe(struct hv_device *dev,
>  	if (!ring_size)
>  		ring_size = SZ_2M;
> 
> +	/*
> +	 * Adjust ring size if necessary to have the ring data region page
> +	 * aligned
> +	 */
> +	ring_size = VMBUS_RING_SIZE(ring_size);
> +
>  	pdata = devm_kzalloc(&dev->device, sizeof(*pdata), GFP_KERNEL);
>  	if (!pdata)
>  		return -ENOMEM;
> --
> 2.34.1
> 

Reviewed-by: Michael Kelley <mhklinux@outlook.com>