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From:   Eli Cohen <elic@nvidia.com>
To:     Jason Wang <jasowang@redhat.com>, "mst@redhat.com" <mst@redhat.com>
CC:     "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Anirudh Rayabharam <mail@anirudhrb.com>
Subject: RE: [PATCH] vhost: allow batching hint without size
Thread-Topic: [PATCH] vhost: allow batching hint without size
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Date:   Thu, 10 Mar 2022 10:59:33 +0000
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References: <20220310075211.4801-1-jasowang@redhat.com>
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Tested-by: Eli Cohen <elic@nvidia.com>

> -----Original Message-----
> From: Jason Wang <jasowang@redhat.com>
> Sent: Thursday, March 10, 2022 9:52 AM
> To: mst@redhat.com
> Cc: kvm@vger.kernel.org; virtualization@lists.linux-foundation.org; netde=
v@vger.kernel.org; linux-kernel@vger.kernel.org; Jason Wang
> <jasowang@redhat.com>; Eli Cohen <elic@nvidia.com>; Anirudh Rayabharam <m=
ail@anirudhrb.com>
> Subject: [PATCH] vhost: allow batching hint without size
>=20
> Commit e2ae38cf3d91 ("vhost: fix hung thread due to erroneous iotlb
> entries") tries to reject the IOTLB message whose size is zero. But
> the size is not necessarily meaningful, one example is the batching
> hint, so the commit breaks that.
>=20
> Fixing this be reject zero size message only if the message is used to
> update/invalidate the IOTLB.
>=20
> Fixes: e2ae38cf3d91 ("vhost: fix hung thread due to erroneous iotlb entri=
es")
> Reported-by: Eli Cohen <elic@nvidia.com>
> Cc: Anirudh Rayabharam <mail@anirudhrb.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  drivers/vhost/vhost.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 082380c03a3e..1768362115c6 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1170,7 +1170,9 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
>  		goto done;
>  	}
>=20
> -	if (msg.size =3D=3D 0) {
> +	if ((msg.type =3D=3D VHOST_IOTLB_UPDATE ||
> +	     msg.type =3D=3D VHOST_IOTLB_INVALIDATE) &&
> +	     msg.size =3D=3D 0) {
>  		ret =3D -EINVAL;
>  		goto done;
>  	}
> --
> 2.18.1