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Date: Wed, 15 Mar 2023 13:59:27 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: jgg@...dia.com, yishaih@...dia.com,
shameerali.kolothum.thodi@...wei.com, kevin.tian@...el.com,
alex.williamson@...hat.com
Cc: tglx@...utronix.de, darwi@...utronix.de, kvm@...r.kernel.org,
dave.jiang@...el.com, jing2.liu@...el.com, ashok.raj@...el.com,
fenghua.yu@...el.com, tom.zanussi@...ux.intel.com,
reinette.chatre@...el.com, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 7/8] vfio/pci: Support dynamic MSI-x
Recently introduced pci_msix_alloc_irq_at() and pci_msix_free_irq()
enables an individual MSI-X index to be allocated and freed after
MSI-X enabling.
Support dynamic MSI-X by keeping the association between allocated
interrupt and vfio interrupt context. Allocate new context together
with the new interrupt if no interrupt context exist for an MSI-X
interrupt. Similarly, release an interrupt with its context.
Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
---
Guidance is appreciated on expectations regarding maintaining
existing error behavior. Earlier patch introduced the
vfio_irq_ctx_range_allocated() helper to maintain existing error
behavior. Now, this helper needs to be disabled for MSI-X. User
space not wanting to dynamically allocate MSI-X interrupts, but
providing invalid range when providing a new ACTION will now
obtain new interrupts or new failures (potentially including freeing
of existing interrupts) if the allocation of the new interrupts fail.
drivers/vfio/pci/vfio_pci_intrs.c | 101 ++++++++++++++++++++++++------
1 file changed, 83 insertions(+), 18 deletions(-)
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index b375a12885ba..954a70575802 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -55,6 +55,18 @@ struct vfio_pci_irq_ctx *vfio_irq_ctx_get(struct vfio_pci_core_device *vdev,
return xa_load(&vdev->ctx, index);
}
+static void vfio_irq_ctx_free(struct vfio_pci_core_device *vdev,
+ unsigned long index)
+{
+ struct vfio_pci_irq_ctx *ctx;
+
+ ctx = xa_load(&vdev->ctx, index);
+ if (ctx) {
+ xa_erase(&vdev->ctx, index);
+ kfree(ctx);
+ }
+}
+
static void vfio_irq_ctx_free_all(struct vfio_pci_core_device *vdev)
{
struct vfio_pci_irq_ctx *ctx;
@@ -430,33 +442,63 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev,
{
struct pci_dev *pdev = vdev->pdev;
struct vfio_pci_irq_ctx *ctx;
+ struct msi_map msix_map = {};
struct eventfd_ctx *trigger;
+ bool new_ctx;
int irq, ret;
u16 cmd;
ctx = vfio_irq_ctx_get(vdev, vector);
- if (!ctx)
+ /* Only MSI-X allows dynamic allocation. */
+ if (!msix && !ctx)
return -EINVAL;
+
irq = pci_irq_vector(pdev, vector);
+ /* Context and interrupt are always allocated together. */
+ WARN_ON((ctx && irq == -EINVAL) || (!ctx && irq != -EINVAL));
- if (ctx->trigger) {
+ if (ctx && ctx->trigger) {
irq_bypass_unregister_producer(&ctx->producer);
cmd = vfio_pci_memory_lock_and_enable(vdev);
free_irq(irq, ctx->trigger);
+ if (msix) {
+ msix_map.index = vector;
+ msix_map.virq = irq;
+ pci_msix_free_irq(pdev, msix_map);
+ irq = -EINVAL;
+ }
vfio_pci_memory_unlock_and_restore(vdev, cmd);
kfree(ctx->name);
eventfd_ctx_put(ctx->trigger);
ctx->trigger = NULL;
+ if (msix) {
+ vfio_irq_ctx_free(vdev, vector);
+ ctx = NULL;
+ }
}
if (fd < 0)
return 0;
+ if (!ctx) {
+ ret = vfio_irq_ctx_alloc_single(vdev, vector);
+ if (ret)
+ return ret;
+ ctx = vfio_irq_ctx_get(vdev, vector);
+ if (!ctx) {
+ ret = -EINVAL;
+ goto out_free_ctx;
+ }
+ new_ctx = true;
+ }
+
ctx->name = kasprintf(GFP_KERNEL_ACCOUNT, "vfio-msi%s[%d](%s)",
msix ? "x" : "", vector, pci_name(pdev));
- if (!ctx->name)
- return -ENOMEM;
+ if (!ctx->name) {
+ ret = -ENOMEM;
+ goto out_free_ctx;
+ }
trigger = eventfd_ctx_fdget(fd);
if (IS_ERR(trigger)) {
@@ -464,25 +506,38 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev,
goto out_free_name;
}
- /*
- * The MSIx vector table resides in device memory which may be cleared
- * via backdoor resets. We don't allow direct access to the vector
- * table so even if a userspace driver attempts to save/restore around
- * such a reset it would be unsuccessful. To avoid this, restore the
- * cached value of the message prior to enabling.
- */
cmd = vfio_pci_memory_lock_and_enable(vdev);
if (msix) {
- struct msi_msg msg;
-
- get_cached_msi_msg(irq, &msg);
- pci_write_msi_msg(irq, &msg);
+ if (irq == -EINVAL) {
+ msix_map = pci_msix_alloc_irq_at(pdev, vector, NULL);
+ if (msix_map.index < 0) {
+ vfio_pci_memory_unlock_and_restore(vdev, cmd);
+ ret = msix_map.index;
+ goto out_put_eventfd_ctx;
+ }
+ irq = msix_map.virq;
+ } else {
+ /*
+ * The MSIx vector table resides in device memory which
+ * may be cleared via backdoor resets. We don't allow
+ * direct access to the vector table so even if a
+ * userspace driver attempts to save/restore around
+ * such a reset it would be unsuccessful. To avoid
+ * this, restore the cached value of the message prior
+ * to enabling.
+ */
+ struct msi_msg msg;
+
+ get_cached_msi_msg(irq, &msg);
+ pci_write_msi_msg(irq, &msg);
+ }
}
ret = request_irq(irq, vfio_msihandler, 0, ctx->name, trigger);
- vfio_pci_memory_unlock_and_restore(vdev, cmd);
if (ret)
- goto out_put_eventfd_ctx;
+ goto out_free_irq_locked;
+
+ vfio_pci_memory_unlock_and_restore(vdev, cmd);
ctx->producer.token = trigger;
ctx->producer.irq = irq;
@@ -498,11 +553,21 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev,
return 0;
+out_free_irq_locked:
+ if (msix && new_ctx) {
+ msix_map.index = vector;
+ msix_map.virq = irq;
+ pci_msix_free_irq(pdev, msix_map);
+ }
+ vfio_pci_memory_unlock_and_restore(vdev, cmd);
out_put_eventfd_ctx:
eventfd_ctx_put(trigger);
out_free_name:
kfree(ctx->name);
ctx->name = NULL;
+out_free_ctx:
+ if (msix && new_ctx)
+ vfio_irq_ctx_free(vdev, vector);
return ret;
}
@@ -512,7 +577,7 @@ static int vfio_msi_set_block(struct vfio_pci_core_device *vdev, unsigned start,
int i, ret = 0;
unsigned int j;
- if (!vfio_irq_ctx_range_allocated(vdev, start, count))
+ if (!msix && !vfio_irq_ctx_range_allocated(vdev, start, count))
return -EINVAL;
for (i = 0, j = start; i < count && !ret; i++, j++) {
--
2.34.1
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