[v1] hv_sock: fix ARM64 support

[PATCH] hv_sock: fix ARM64 support

Posted by Hamza Mahfooz 1 month, 2 weeks ago

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

Re: [PATCH] hv_sock: fix ARM64 support

Posted by Stefano Garzarella 1 month, 2 weeks ago

On Tue, Apr 28, 2026 at 07:05:30AM -0400, 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.
>
>Cc: stable@kernel.vger.org

mmm, this is the first time I've seen this address used for stable. Even 
after searching in the log, I don't see anyone else who's used it.
Where did you get it from?

 From Documentation/process/stable-kernel-rules.rst :

   To have a patch you submit for mainline inclusion later automatically 
   picked up for stable trees, add this tag in the sign-off area::

     Cc: stable@vger.kernel.org


The patch LGTM.

Thanks,
Stefano

>Fixes: 77ffe33363c0 ("hv_sock: use HV_HYP_PAGE_SIZE for Hyper-V communication")
>Tested-by: Dexuan Cui <decui@microsoft.com>
>Reviewed-by: Dexuan Cui <decui@microsoft.com>
>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
>

Re: [PATCH] hv_sock: fix ARM64 support

Posted by Hamza Mahfooz 1 month, 2 weeks ago

On Tue, Apr 28, 2026 at 02:15:26PM +0200, Stefano Garzarella wrote:
> On Tue, Apr 28, 2026 at 07:05:30AM -0400, 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.
> > 
> > Cc: stable@kernel.vger.org
> 
> mmm, this is the first time I've seen this address used for stable. Even
> after searching in the log, I don't see anyone else who's used it.
> Where did you get it from?
> 
> From Documentation/process/stable-kernel-rules.rst :
> 
>   To have a patch you submit for mainline inclusion later automatically
> picked up for stable trees, add this tag in the sign-off area::
> 
>     Cc: stable@vger.kernel.org

Ya, that is the address I intended to Cc, not sure how I ended up
mangling it though.

> 
> 
> The patch LGTM.
> 
> Thanks,
> Stefano
> 
> > Fixes: 77ffe33363c0 ("hv_sock: use HV_HYP_PAGE_SIZE for Hyper-V communication")
> > Tested-by: Dexuan Cui <decui@microsoft.com>
> > Reviewed-by: Dexuan Cui <decui@microsoft.com>
> > 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
> > 
>