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Message-ID: <e73fe624-6e87-673e-b023-80cb8a0cf5f4@nvidia.com>
Date: Wed, 6 Jul 2022 23:08:48 +0530
From: Kirti Wankhede <kwankhede@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>, corbet@....net,
hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
zhenyuw@...ux.intel.com, zhi.a.wang@...el.com,
jani.nikula@...ux.intel.com, joonas.lahtinen@...ux.intel.com,
rodrigo.vivi@...el.com, tvrtko.ursulin@...ux.intel.com,
airlied@...ux.ie, daniel@...ll.ch, farman@...ux.ibm.com,
mjrosato@...ux.ibm.com, pasic@...ux.ibm.com, vneethv@...ux.ibm.com,
oberpar@...ux.ibm.com, freude@...ux.ibm.com,
akrowiak@...ux.ibm.com, jjherne@...ux.ibm.com,
alex.williamson@...hat.com, cohuck@...hat.com, jgg@...dia.com,
kevin.tian@...el.com, hch@...radead.org
Cc: jchrist@...ux.ibm.com, kvm@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org, intel-gvt-dev@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
Neo Jia <cjia@...dia.com>, Tarun Gupta <targupta@...dia.com>,
Shounak Deshpande <shdeshpande@...dia.com>
Subject: Re: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin_pages() return void
Reviewed-by: Kirti Wankhede <kwankhede@...dia.com>
On 7/6/2022 11:57 AM, Nicolin Chen wrote:
> There's only one caller that checks its return value with a WARN_ON_ONCE,
> while all other callers do not check return value at all. So simplify the
> API to return void by embedding similar WARN_ON_ONCEs.
>
> Suggested-by: Christoph Hellwig <hch@...radead.org>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
> .../driver-api/vfio-mediated-device.rst | 2 +-
> drivers/gpu/drm/i915/gvt/kvmgt.c | 5 +---
> drivers/vfio/vfio.c | 24 ++++++++-----------
> drivers/vfio/vfio.h | 2 +-
> drivers/vfio/vfio_iommu_type1.c | 16 ++++++-------
> include/linux/vfio.h | 4 ++--
> 6 files changed, 23 insertions(+), 30 deletions(-)
>
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
> index 1c57815619fd..b0fdf76b339a 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -265,7 +265,7 @@ driver::
> int vfio_pin_pages(struct vfio_device *device, unsigned long *user_pfn,
> int npage, int prot, unsigned long *phys_pfn);
>
> - int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> + void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> int npage);
>
> These functions call back into the back-end IOMMU module by using the pin_pages
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index e2f6c56ab342..8c67c9aba82d 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -231,18 +231,15 @@ static void intel_gvt_cleanup_vgpu_type_groups(struct intel_gvt *gvt)
> static void gvt_unpin_guest_page(struct intel_vgpu *vgpu, unsigned long gfn,
> unsigned long size)
> {
> - struct drm_i915_private *i915 = vgpu->gvt->gt->i915;
> int total_pages;
> int npage;
> - int ret;
>
> total_pages = roundup(size, PAGE_SIZE) / PAGE_SIZE;
>
> for (npage = 0; npage < total_pages; npage++) {
> unsigned long cur_gfn = gfn + npage;
>
> - ret = vfio_unpin_pages(&vgpu->vfio_device, &cur_gfn, 1);
> - drm_WARN_ON(&i915->drm, ret != 1);
> + vfio_unpin_pages(&vgpu->vfio_device, &cur_gfn, 1);
> }
> }
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 61e71c1154be..01f45ec70a3d 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -1959,31 +1959,27 @@ EXPORT_SYMBOL(vfio_pin_pages);
> * PFNs should not be greater than VFIO_PIN_PAGES_MAX_ENTRIES.
> * @npage [in] : count of elements in user_pfn array. This count should not
> * be greater than VFIO_PIN_PAGES_MAX_ENTRIES.
> - * Return error or number of pages unpinned.
> */
> -int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> - int npage)
> +void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> + int npage)
> {
> struct vfio_container *container;
> struct vfio_iommu_driver *driver;
> - int ret;
>
> - if (!user_pfn || !npage || !vfio_assert_device_open(device))
> - return -EINVAL;
> + if (WARN_ON_ONCE(!user_pfn || !npage || !vfio_assert_device_open(device)))
> + return;
>
> - if (npage > VFIO_PIN_PAGES_MAX_ENTRIES)
> - return -E2BIG;
> + if (WARN_ON_ONCE(npage > VFIO_PIN_PAGES_MAX_ENTRIES))
> + return;
>
> /* group->container cannot change while a vfio device is open */
> container = device->group->container;
> driver = container->iommu_driver;
> - if (likely(driver && driver->ops->unpin_pages))
> - ret = driver->ops->unpin_pages(container->iommu_data, user_pfn,
> - npage);
> - else
> - ret = -ENOTTY;
>
> - return ret;
> + if (WARN_ON_ONCE(unlikely(!driver || !driver->ops->unpin_pages)))
> + return;
> +
> + driver->ops->unpin_pages(container->iommu_data, user_pfn, npage);
> }
> EXPORT_SYMBOL(vfio_unpin_pages);
>
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index a67130221151..bef4edf58138 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -53,7 +53,7 @@ struct vfio_iommu_driver_ops {
> unsigned long *user_pfn,
> int npage, int prot,
> unsigned long *phys_pfn);
> - int (*unpin_pages)(void *iommu_data,
> + void (*unpin_pages)(void *iommu_data,
> unsigned long *user_pfn, int npage);
> int (*register_notifier)(void *iommu_data,
> unsigned long *events,
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index c13b9290e357..08613edaf722 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -948,20 +948,19 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
> return ret;
> }
>
> -static int vfio_iommu_type1_unpin_pages(void *iommu_data,
> - unsigned long *user_pfn,
> - int npage)
> +static void vfio_iommu_type1_unpin_pages(void *iommu_data,
> + unsigned long *user_pfn, int npage)
> {
> struct vfio_iommu *iommu = iommu_data;
> bool do_accounting;
> int i;
>
> - if (!iommu || !user_pfn || npage <= 0)
> - return -EINVAL;
> + if (WARN_ON_ONCE(!iommu || !user_pfn || npage <= 0))
> + return;
>
> /* Supported for v2 version only */
> - if (!iommu->v2)
> - return -EACCES;
> + if (WARN_ON_ONCE(!iommu->v2))
> + return;
>
> mutex_lock(&iommu->lock);
>
> @@ -979,7 +978,8 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
> }
>
> mutex_unlock(&iommu->lock);
> - return i > 0 ? i : -EINVAL;
> +
> + WARN_ON_ONCE(i != npage);
> }
>
> static long vfio_sync_unpin(struct vfio_dma *dma, struct vfio_domain *domain,
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 49580fa2073a..d0844ecdc961 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -149,8 +149,8 @@ bool vfio_file_has_dev(struct file *file, struct vfio_device *device);
>
> int vfio_pin_pages(struct vfio_device *device, unsigned long *user_pfn,
> int npage, int prot, unsigned long *phys_pfn);
> -int vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> - int npage);
> +void vfio_unpin_pages(struct vfio_device *device, unsigned long *user_pfn,
> + int npage);
> int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova,
> void *data, size_t len, bool write);
>
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