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[94.66.118.61]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49807eb12c5sm3178825e9.3.2026.07.31.17.00.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Jul 2026 17:00:15 -0700 (PDT) Date: Fri, 31 Jul 2026 20:00:12 -0400 From: "Michael S. Tsirkin" To: Dongli Zhang Cc: virtualization@lists.linux.dev, jasowangio@gmail.com, michael.christie@oracle.com, pbonzini@redhat.com, stefanha@redhat.com, eperezma@redhat.com, kvm@vger.kernel.org, joe.jin@oracle.com Subject: Re: [PATCH 2/2] vhost-scsi: reject invalid max_io_vqs module parameter Message-ID: <20260731195756-mutt-send-email-mst@kernel.org> References: <20260731221116.236791-1-dongli.zhang@oracle.com> <20260731221116.236791-3-dongli.zhang@oracle.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260731221116.236791-3-dongli.zhang@oracle.com> On Fri, Jul 31, 2026 at 03:10:24PM -0700, Dongli Zhang wrote: > max_io_vqs is currently validated only when a vhost-scsi device is opened. > This allows sysfs to show values larger than the driver will actually use, > e.g. writing 2048 succeeds even though vhost_scsi_open() later clamps it to > VHOST_SCSI_MAX_IO_VQ. This makes the sysfs value differ from the value that > will actually be used. > > hv# echo 2048 > /sys/module/vhost_scsi/parameters/max_io_vqs > > hv# cat /sys/module/vhost_scsi/parameters/max_io_vqs > 2048 > > [ 315.630495] Invalid max_io_vqs of 2048. Using 1024. > > Use a module parameter callback to reject out-of-range updates when the > parameter is written. This keeps the visible parameter value consistent > with the effective queue limit. > > With the parameter value kept in range, remove the duplicate validation > from vhost_scsi_open(). > > Invalid values now fail with -EINVAL at write/load time instead of being > accepted and silently adjusted later when the device is opened. > > Signed-off-by: Dongli Zhang why should we change userspace visible behaviour now? > --- > drivers/vhost/scsi.c | 27 ++++++++++++++++----------- > 1 file changed, 16 insertions(+), 11 deletions(-) > > diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c > index 0c0634eea144..c138c29ce3dd 100644 > --- a/drivers/vhost/scsi.c > +++ b/drivers/vhost/scsi.c > @@ -210,7 +210,20 @@ static const int vhost_scsi_bits[] = { > #define VHOST_SCSI_MAX_EVENT 128 > > static unsigned vhost_scsi_max_io_vqs = 128; > -module_param_named(max_io_vqs, vhost_scsi_max_io_vqs, uint, 0644); > + > +static int vhost_scsi_set_max_io_vqs(const char *val, > + const struct kernel_param *kp) > +{ > + return param_set_uint_minmax(val, kp, 1, VHOST_SCSI_MAX_IO_VQ); > +} > + > +static const struct kernel_param_ops vhost_scsi_max_io_vqs_op = { > + .set = vhost_scsi_set_max_io_vqs, > + .get = param_get_uint, > +}; > + > +module_param_cb(max_io_vqs, &vhost_scsi_max_io_vqs_op, > + &vhost_scsi_max_io_vqs, 0644); > MODULE_PARM_DESC(max_io_vqs, "Set the max number of IO virtqueues a vhost scsi device can support. The default is 128. The max is 1024."); > > struct vhost_scsi_virtqueue { > @@ -2273,22 +2286,14 @@ static int vhost_scsi_open(struct inode *inode, struct file *f) > struct vhost_scsi_virtqueue *svq; > struct vhost_scsi *vs; > struct vhost_virtqueue **vqs; > - int r = -ENOMEM, i, nvqs = vhost_scsi_max_io_vqs; > + int r = -ENOMEM, i, nvqs; > > vs = kvzalloc_obj(*vs); > if (!vs) > goto err_vs; > vs->inline_sg_cnt = vhost_scsi_inline_sg_cnt; > > - if (nvqs > VHOST_SCSI_MAX_IO_VQ) { > - pr_err("Invalid max_io_vqs of %d. Using %d.\n", nvqs, > - VHOST_SCSI_MAX_IO_VQ); > - nvqs = VHOST_SCSI_MAX_IO_VQ; > - } else if (nvqs == 0) { > - pr_err("Invalid max_io_vqs of %d. Using 1.\n", nvqs); > - nvqs = 1; > - } > - nvqs += VHOST_SCSI_VQ_IO; > + nvqs = vhost_scsi_max_io_vqs + VHOST_SCSI_VQ_IO; > > vs->old_inflight = kmalloc_objs(*vs->old_inflight, nvqs, > GFP_KERNEL | __GFP_ZERO); > -- > 2.43.5