[PATCH v2 2/3] vfio/pci: Replace vfio_pci_core_setup_barmap() with checks for resource/map

[Matt Evans <mattev@meta.com>]

Since "vfio/pci: Set up barmap in vfio_pci_core_enable()", the
resource request and iomap for the BARs was performed early, and
vfio_pci_core_setup_barmap() now just checks those actions succeeded.

There were two types of callers:
 - Those that need the iomap, because they'll access the BAR
 - Those that need the resource, because they'll map/export it

This replaces vfio_pci_core_setup_barmap() with two helpers,
vfio_pci_core_check_barmap_valid() and vfio_pci_core_check_bar_rsrc(),
to make it clear which behaviour is required in each caller.

Signed-off-by: Matt Evans <mattev@meta.com>
---
 drivers/vfio/pci/nvgrace-gpu/main.c |  8 +++-----
 drivers/vfio/pci/vfio_pci_core.c    |  5 ++---
 drivers/vfio/pci/vfio_pci_rdwr.c    | 22 ++--------------------
 drivers/vfio/pci/virtio/legacy_io.c |  4 ++--
 include/linux/vfio_pci_core.h       | 23 ++++++++++++++++++++++-
 5 files changed, 31 insertions(+), 31 deletions(-)

diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
index fa056b69f899..d5f09144ac84 100644
--- a/drivers/vfio/pci/nvgrace-gpu/main.c
+++ b/drivers/vfio/pci/nvgrace-gpu/main.c
@@ -184,12 +184,10 @@ static int nvgrace_gpu_open_device(struct vfio_device *core_vdev)
 
 	/*
 	 * GPU readiness is checked by reading the BAR0 registers.
-	 *
-	 * ioremap BAR0 to ensure that the BAR0 mapping is present before
-	 * register reads on first fault before establishing any GPU
-	 * memory mapping.
+	 * Ensure that the BAR0 mapping is present before that
+	 * happens.
 	 */
-	ret = vfio_pci_core_setup_barmap(vdev, 0);
+	ret = vfio_pci_core_check_barmap_valid(vdev, 0);
 	if (ret)
 		goto error_exit;
 
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index c59c61861d81..2771d0f21899 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1804,10 +1804,9 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma
 		return -EINVAL;
 
 	/*
-	 * Even though we don't make use of the barmap for the mmap,
-	 * we need to request the region and the barmap tracks that.
+	 * Ensure the BAR resource region is reserved for use.
 	 */
-	ret = vfio_pci_core_setup_barmap(vdev, index);
+	ret = vfio_pci_core_check_bar_rsrc(vdev, index);
 	if (ret)
 		return ret;
 
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index bf7152316db4..40c97d73ff95 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -198,24 +198,6 @@ ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem,
 }
 EXPORT_SYMBOL_GPL(vfio_pci_core_do_io_rw);
 
-int vfio_pci_core_setup_barmap(struct vfio_pci_core_device *vdev, int bar)
-{
-	/*
-	 * The barmap is now always set up in vfio_pci_core_enable().
-	 * Some legacy callers use this function to ensure the BAR
-	 * resources are requested, and others to ensure the
-	 * pci_iomap() was done, so check here:
-	 */
-	if (bar < 0 || bar >= PCI_STD_NUM_BARS)
-		return -EINVAL;
-	if (vdev->barmap[bar] == 0)
-		return -ENOMEM;
-	if (!vdev->bar_has_rsrc[bar])
-		return -EBUSY;
-	return 0;
-}
-EXPORT_SYMBOL_GPL(vfio_pci_core_setup_barmap);
-
 ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
 			size_t count, loff_t *ppos, bool iswrite)
 {
@@ -267,7 +249,7 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
 		 */
 		max_width = VFIO_PCI_IO_WIDTH_4;
 	} else {
-		int ret = vfio_pci_core_setup_barmap(vdev, bar);
+		int ret = vfio_pci_core_check_barmap_valid(vdev, bar);
 		if (ret) {
 			done = ret;
 			goto out;
@@ -445,7 +427,7 @@ int vfio_pci_ioeventfd(struct vfio_pci_core_device *vdev, loff_t offset,
 	if (count == 8)
 		return -EINVAL;
 
-	ret = vfio_pci_core_setup_barmap(vdev, bar);
+	ret = vfio_pci_core_check_barmap_valid(vdev, bar);
 	if (ret)
 		return ret;
 
diff --git a/drivers/vfio/pci/virtio/legacy_io.c b/drivers/vfio/pci/virtio/legacy_io.c
index 1ed349a55629..9c59d1600ac4 100644
--- a/drivers/vfio/pci/virtio/legacy_io.c
+++ b/drivers/vfio/pci/virtio/legacy_io.c
@@ -305,8 +305,8 @@ static int virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
 	 * Setup the BAR where the 'notify' exists to be used by vfio as well
 	 * This will let us mmap it only once and use it when needed.
 	 */
-	ret = vfio_pci_core_setup_barmap(core_device,
-					 virtvdev->notify_bar);
+	ret = vfio_pci_core_check_barmap_valid(core_device,
+					       virtvdev->notify_bar);
 	if (ret)
 		return ret;
 
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index 1f508b067d82..6a5384d57f1d 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -189,7 +189,6 @@ int vfio_pci_core_match_token_uuid(struct vfio_device *core_vdev,
 int vfio_pci_core_enable(struct vfio_pci_core_device *vdev);
 void vfio_pci_core_disable(struct vfio_pci_core_device *vdev);
 void vfio_pci_core_finish_enable(struct vfio_pci_core_device *vdev);
-int vfio_pci_core_setup_barmap(struct vfio_pci_core_device *vdev, int bar);
 pci_ers_result_t vfio_pci_core_aer_err_detected(struct pci_dev *pdev,
 						pci_channel_state_t state);
 ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem,
@@ -225,6 +224,28 @@ VFIO_IOREAD_DECLARATION(32)
 VFIO_IOREAD_DECLARATION(64)
 #endif
 
+/* Returns 0 if vdev->barmap[bar] can be accessed, otherwise errno */
+static inline int
+vfio_pci_core_check_barmap_valid(struct vfio_pci_core_device *vdev, int bar)
+{
+	if (bar < 0 || bar >= PCI_STD_NUM_BARS)
+		return -EINVAL;
+	if (vdev->barmap[bar] == 0)
+		return -ENOMEM;
+	return 0;
+}
+
+/* Returns 0 if BAR has a valid resource reserved for use, otherwise errno */
+static inline int vfio_pci_core_check_bar_rsrc(struct vfio_pci_core_device *vdev,
+					       int bar)
+{
+	if (bar < 0 || bar >= PCI_STD_NUM_BARS)
+		return -EINVAL;
+	if (!vdev->have_bar_resource[bar])
+		return -EBUSY;
+	return 0;
+}
+
 static inline bool is_aligned_for_order(struct vm_area_struct *vma,
 					unsigned long addr,
 					unsigned long pfn,
-- 
2.47.3