[PATCH 1/2] hv_sock: fix ARM64 support

[PATCH 1/2] hv_sock: fix ARM64 support

[Hamza Mahfooz]

VMBUS ring buffers must be page aligned. Therefore, the current value of
24K presents a challenge on ARM64 kernels (with 64K pages). So, use
VMBUS_RING_SIZE() to ensure they are always aligned and large enough to
hold all of the relevant data.

Cc: stable@kernel.vger.org
Fixes: 77ffe33363c0 ("hv_sock: use HV_HYP_PAGE_SIZE for Hyper-V communication")
Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
---
 net/vmw_vsock/hyperv_transport.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index 069386a74557..40f09b23efa3 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -375,10 +375,10 @@ static void hvs_open_connection(struct vmbus_channel *chan)
 	} else {
 		sndbuf = max_t(int, sk->sk_sndbuf, RINGBUFFER_HVS_SND_SIZE);
 		sndbuf = min_t(int, sndbuf, RINGBUFFER_HVS_MAX_SIZE);
-		sndbuf = ALIGN(sndbuf, HV_HYP_PAGE_SIZE);
+		sndbuf = VMBUS_RING_SIZE(sndbuf);
 		rcvbuf = max_t(int, sk->sk_rcvbuf, RINGBUFFER_HVS_RCV_SIZE);
 		rcvbuf = min_t(int, rcvbuf, RINGBUFFER_HVS_MAX_SIZE);
-		rcvbuf = ALIGN(rcvbuf, HV_HYP_PAGE_SIZE);
+		rcvbuf = VMBUS_RING_SIZE(rcvbuf);
 	}
 
 	chan->max_pkt_size = HVS_MAX_PKT_SIZE;
-- 
2.54.0

[PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()

[Hamza Mahfooz]

VMBUS ring buffers must be page aligned. So, use VMBUS_RING_SIZE() to
ensure they are always aligned and large enough to hold all of the
relevant data.

Cc: stable@kernel.vger.org
Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic video device")
Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
---
 drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
index 051ecc526832..753d97bff76f 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
@@ -10,7 +10,7 @@
 
 #include "hyperv_drm.h"
 
-#define VMBUS_RING_BUFSIZE (256 * 1024)
+#define VMBUS_RING_BUFSIZE VMBUS_RING_SIZE(256 * 1024)
 #define VMBUS_VSP_TIMEOUT (10 * HZ)
 
 #define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
-- 
2.54.0

RE: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()

[Saurabh Singh Sengar]

> Subject: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()
> 
> VMBUS ring buffers must be page aligned. So, use VMBUS_RING_SIZE() to
> ensure they are always aligned and large enough to hold all of the relevant
> data.
> 
> Cc: stable@kernel.vger.org
> Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic video
> device")
> Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> ---
>  drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> index 051ecc526832..753d97bff76f 100644
> --- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> +++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> @@ -10,7 +10,7 @@
> 
>  #include "hyperv_drm.h"
> 
> -#define VMBUS_RING_BUFSIZE (256 * 1024)
> +#define VMBUS_RING_BUFSIZE VMBUS_RING_SIZE(256 * 1024)
>  #define VMBUS_VSP_TIMEOUT (10 * HZ)
> 
>  #define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
> --
> 2.54.0

Although this lgtm, but this may change the behaviour on ARM64 systems with page size > 4K ?
Have we tested it ?

Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>

Re: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()

[Hamza Mahfooz]

On Sun, Apr 26, 2026 at 05:00:24AM +0000, Saurabh Singh Sengar wrote:
> > Subject: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()
> > 
> > VMBUS ring buffers must be page aligned. So, use VMBUS_RING_SIZE() to
> > ensure they are always aligned and large enough to hold all of the relevant
> > data.
> > 
> > Cc: stable@kernel.vger.org
> > Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic video
> > device")
> > Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> > ---
> >  drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > index 051ecc526832..753d97bff76f 100644
> > --- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > +++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > @@ -10,7 +10,7 @@
> > 
> >  #include "hyperv_drm.h"
> > 
> > -#define VMBUS_RING_BUFSIZE (256 * 1024)
> > +#define VMBUS_RING_BUFSIZE VMBUS_RING_SIZE(256 * 1024)
> >  #define VMBUS_VSP_TIMEOUT (10 * HZ)
> > 
> >  #define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
> > --
> > 2.54.0
> 
> Although this lgtm, but this may change the behaviour on ARM64 systems with page size > 4K ?
> Have we tested it ?

Yup, I tested it on an ARM64 windows machine with a 64K page size guest kernel.

> 
> Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>

Pushed to drm-misc.

> 

RE: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()

[Dexuan Cui]

> From: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> Sent: Monday, April 27, 2026 4:52 AM
> To: Saurabh Singh Sengar <ssengar@microsoft.com>
> ...
> On Sun, Apr 26, 2026 at 05:00:24AM +0000, Saurabh Singh Sengar wrote:
> > > Subject: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()
> > >
> > > VMBUS ring buffers must be page aligned. So, use VMBUS_RING_SIZE() to
> > > ensure they are always aligned and large enough to hold all of the relevant
> > > data.
> > >
> > > Cc: stable@kernel.vger.org
> > > Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic
> > >  video device")

IMO the Fixes tag is unnecessary because the existing VMBUS_RING_BUFSIZE
is 256KB, which is already aligned to 4KB, 16KB and 64KB.

VMBUS_RING_SIZE(256 * 1024) is still 256KB.

> > > Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> > > ---
> > >  drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > index 051ecc526832..753d97bff76f 100644
> > > --- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > +++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > @@ -10,7 +10,7 @@
> > >
> > >  #include "hyperv_drm.h"
> > >
> > > -#define VMBUS_RING_BUFSIZE (256 * 1024)
> > > +#define VMBUS_RING_BUFSIZE VMBUS_RING_SIZE(256 * 1024)
> > >  #define VMBUS_VSP_TIMEOUT (10 * HZ)
> > >
> > >  #define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
> > > --
> > > 2.54.0
> >
> > Although this lgtm, but this may change the behaviour on ARM64 systems
> with page size > 4K ?

Actually the behavior won't change, because
VMBUS_RING_SIZE(256 * 1024) is still 256KB.

> > Have we tested it ?
> 
> Yup, I tested it on an ARM64 windows machine with a 64K page size guest
> kernel.
> 
> >
> > Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> 
> Pushed to drm-misc.

RE: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()

[Michael Kelley]

From: Dexuan Cui <DECUI@microsoft.com> Sent: Monday, April 27, 2026 11:42 AM
> 
> > From: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> > Sent: Monday, April 27, 2026 4:52 AM
> > To: Saurabh Singh Sengar <ssengar@microsoft.com>
> > ...
> > On Sun, Apr 26, 2026 at 05:00:24AM +0000, Saurabh Singh Sengar wrote:
> > > > Subject: [PATCH 2/2] drm/hyperv: use VMBUS_RING_SIZE()
> > > >
> > > > VMBUS ring buffers must be page aligned. So, use VMBUS_RING_SIZE() to
> > > > ensure they are always aligned and large enough to hold all of the relevant
> > > > data.
> > > >
> > > > Cc: stable@kernel.vger.org
> > > > Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic
> > > >  video device")
> 
> IMO the Fixes tag is unnecessary because the existing VMBUS_RING_BUFSIZE
> is 256KB, which is already aligned to 4KB, 16KB and 64KB.
> 
> VMBUS_RING_SIZE(256 * 1024) is still 256KB.

Not always. If PAGE_SIZE is 64KiB, VMBUS_RING_SIZE(256 * 1024) is
320KiB. If PAGE_SIZE is 16KiB or 4KiB, then VMBUS_RING_SIZE(256 * 1024)
is indeed 256 KiB. See the explanation in the comment for VMBUS_RING_SIZE.

Michael

> 
> > > > Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> > > > ---
> > > >  drivers/gpu/drm/hyperv/hyperv_drm_proto.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > > b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > > index 051ecc526832..753d97bff76f 100644
> > > > --- a/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > > +++ b/drivers/gpu/drm/hyperv/hyperv_drm_proto.c
> > > > @@ -10,7 +10,7 @@
> > > >
> > > >  #include "hyperv_drm.h"
> > > >
> > > > -#define VMBUS_RING_BUFSIZE (256 * 1024)
> > > > +#define VMBUS_RING_BUFSIZE VMBUS_RING_SIZE(256 * 1024)
> > > >  #define VMBUS_VSP_TIMEOUT (10 * HZ)
> > > >
> > > >  #define SYNTHVID_VERSION(major, minor) ((minor) << 16 | (major))
> > > > --
> > > > 2.54.0
> > >
> > > Although this lgtm, but this may change the behaviour on ARM64 systems
> > with page size > 4K ?
> 
> Actually the behavior won't change, because
> VMBUS_RING_SIZE(256 * 1024) is still 256KB.
> 
> > > Have we tested it ?
> >
> > Yup, I tested it on an ARM64 windows machine with a 64K page size guest
> > kernel.
> >
> > >
> > > Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> >
> > Pushed to drm-misc.

RE: [PATCH 1/2] hv_sock: fix ARM64 support

[Dexuan Cui]

> From: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> Sent: Saturday, April 25, 2026 11:17 AM
> ...
> Cc: stable@kernel.vger.org
> Fixes: 77ffe33363c0 ("hv_sock: use HV_HYP_PAGE_SIZE for Hyper-V
> communication")

It looks like 77ffe33363c0 was not tested with
CONFIG_ARM64_64K_PAGES=y...

Thanks for the fix!

> Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>

Tested-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>

Re: [PATCH 1/2] hv_sock: fix ARM64 support

[Jakub Kicinski]

On Sat, 25 Apr 2026 11:17:18 -0700 Hamza Mahfooz wrote:
> VMBUS ring buffers must be page aligned. Therefore, the current value of
> 24K presents a challenge on ARM64 kernels (with 64K pages). So, use
> VMBUS_RING_SIZE() to ensure they are always aligned and large enough to
> hold all of the relevant data.

Please split the fixes into two independent postings.
They have to go via different trees AFAICT