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authorLinus Torvalds <torvalds@linux-foundation.org>2018-04-06 19:44:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-06 19:44:27 -0700
commitf605ba97fb80522656c7dce9825a908f1e765b57 (patch)
treecd7d7e1ebd2d59562a61ee45c350392ab00c7ed6
parent016c6f25d11af187f93324d5c591f5d6f63dfb75 (diff)
parentda9147140fe3de5a3a3fe5fe7f69739d4f39bea1 (diff)
downloadlinux-f605ba97fb80522656c7dce9825a908f1e765b57.tar.bz2
Merge tag 'vfio-v4.17-rc1' of git://github.com/awilliam/linux-vfio
Pull VFIO updates from Alex Williamson: - Adopt iommu_unmap_fast() interface to type1 backend (Suravee Suthikulpanit) - mdev sample driver fixup (Shunyong Yang) - More efficient PFN mapping handling in type1 backend (Jason Cai) - VFIO device ioeventfd interface (Alex Williamson) - Tag new vfio-platform sub-maintainer (Alex Williamson) * tag 'vfio-v4.17-rc1' of git://github.com/awilliam/linux-vfio: MAINTAINERS: vfio/platform: Update sub-maintainer vfio/pci: Add ioeventfd support vfio/pci: Use endian neutral helpers vfio/pci: Pull BAR mapping setup from read-write path vfio/type1: Improve memory pinning process for raw PFN mapping vfio-mdev/samples: change RDI interrupt condition vfio/type1: Adopt fast IOTLB flush interface when unmap IOVAs
-rw-r--r--MAINTAINERS2
-rw-r--r--drivers/vfio/pci/vfio_pci.c35
-rw-r--r--drivers/vfio/pci/vfio_pci_private.h19
-rw-r--r--drivers/vfio/pci/vfio_pci_rdwr.c184
-rw-r--r--drivers/vfio/vfio_iommu_type1.c151
-rw-r--r--include/uapi/linux/vfio.h27
-rw-r--r--samples/vfio-mdev/mtty.c2
7 files changed, 377 insertions, 43 deletions
diff --git a/MAINTAINERS b/MAINTAINERS
index 83f5a6fd7de3..7e48624f4f9f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14797,7 +14797,7 @@ F: include/linux/mdev.h
F: samples/vfio-mdev/
VFIO PLATFORM DRIVER
-M: Baptiste Reynal <b.reynal@virtualopensystems.com>
+M: Eric Auger <eric.auger@redhat.com>
L: kvm@vger.kernel.org
S: Maintained
F: drivers/vfio/platform/
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 8a1508a8e481..b423a309a6e0 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -302,6 +302,7 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
{
struct pci_dev *pdev = vdev->pdev;
struct vfio_pci_dummy_resource *dummy_res, *tmp;
+ struct vfio_pci_ioeventfd *ioeventfd, *ioeventfd_tmp;
int i, bar;
/* Stop the device from further DMA */
@@ -311,6 +312,15 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
VFIO_IRQ_SET_ACTION_TRIGGER,
vdev->irq_type, 0, 0, NULL);
+ /* Device closed, don't need mutex here */
+ list_for_each_entry_safe(ioeventfd, ioeventfd_tmp,
+ &vdev->ioeventfds_list, next) {
+ vfio_virqfd_disable(&ioeventfd->virqfd);
+ list_del(&ioeventfd->next);
+ kfree(ioeventfd);
+ }
+ vdev->ioeventfds_nr = 0;
+
vdev->virq_disabled = false;
for (i = 0; i < vdev->num_regions; i++)
@@ -1009,6 +1019,28 @@ hot_reset_release:
kfree(groups);
return ret;
+ } else if (cmd == VFIO_DEVICE_IOEVENTFD) {
+ struct vfio_device_ioeventfd ioeventfd;
+ int count;
+
+ minsz = offsetofend(struct vfio_device_ioeventfd, fd);
+
+ if (copy_from_user(&ioeventfd, (void __user *)arg, minsz))
+ return -EFAULT;
+
+ if (ioeventfd.argsz < minsz)
+ return -EINVAL;
+
+ if (ioeventfd.flags & ~VFIO_DEVICE_IOEVENTFD_SIZE_MASK)
+ return -EINVAL;
+
+ count = ioeventfd.flags & VFIO_DEVICE_IOEVENTFD_SIZE_MASK;
+
+ if (hweight8(count) != 1 || ioeventfd.fd < -1)
+ return -EINVAL;
+
+ return vfio_pci_ioeventfd(vdev, ioeventfd.offset,
+ ioeventfd.data, count, ioeventfd.fd);
}
return -ENOTTY;
@@ -1171,6 +1203,8 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
vdev->irq_type = VFIO_PCI_NUM_IRQS;
mutex_init(&vdev->igate);
spin_lock_init(&vdev->irqlock);
+ mutex_init(&vdev->ioeventfds_lock);
+ INIT_LIST_HEAD(&vdev->ioeventfds_list);
ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
if (ret) {
@@ -1212,6 +1246,7 @@ static void vfio_pci_remove(struct pci_dev *pdev)
vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
kfree(vdev->region);
+ mutex_destroy(&vdev->ioeventfds_lock);
kfree(vdev);
if (vfio_pci_is_vga(pdev)) {
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index f561ac1c78a0..cde3b5d3441a 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -29,6 +29,19 @@
#define PCI_CAP_ID_INVALID 0xFF /* default raw access */
#define PCI_CAP_ID_INVALID_VIRT 0xFE /* default virt access */
+/* Cap maximum number of ioeventfds per device (arbitrary) */
+#define VFIO_PCI_IOEVENTFD_MAX 1000
+
+struct vfio_pci_ioeventfd {
+ struct list_head next;
+ struct virqfd *virqfd;
+ void __iomem *addr;
+ uint64_t data;
+ loff_t pos;
+ int bar;
+ int count;
+};
+
struct vfio_pci_irq_ctx {
struct eventfd_ctx *trigger;
struct virqfd *unmask;
@@ -92,9 +105,12 @@ struct vfio_pci_device {
bool nointx;
struct pci_saved_state *pci_saved_state;
int refcnt;
+ int ioeventfds_nr;
struct eventfd_ctx *err_trigger;
struct eventfd_ctx *req_trigger;
struct list_head dummy_resources_list;
+ struct mutex ioeventfds_lock;
+ struct list_head ioeventfds_list;
};
#define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX)
@@ -120,6 +136,9 @@ extern ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
extern ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
size_t count, loff_t *ppos, bool iswrite);
+extern long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
+ uint64_t data, int count, int fd);
+
extern int vfio_pci_init_perm_bits(void);
extern void vfio_pci_uninit_perm_bits(void);
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index 357243d76f10..a6029d0a5524 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -17,10 +17,29 @@
#include <linux/pci.h>
#include <linux/uaccess.h>
#include <linux/io.h>
+#include <linux/vfio.h>
#include <linux/vgaarb.h>
#include "vfio_pci_private.h"
+#ifdef __LITTLE_ENDIAN
+#define vfio_ioread64 ioread64
+#define vfio_iowrite64 iowrite64
+#define vfio_ioread32 ioread32
+#define vfio_iowrite32 iowrite32
+#define vfio_ioread16 ioread16
+#define vfio_iowrite16 iowrite16
+#else
+#define vfio_ioread64 ioread64be
+#define vfio_iowrite64 iowrite64be
+#define vfio_ioread32 ioread32be
+#define vfio_iowrite32 iowrite32be
+#define vfio_ioread16 ioread16be
+#define vfio_iowrite16 iowrite16be
+#endif
+#define vfio_ioread8 ioread8
+#define vfio_iowrite8 iowrite8
+
/*
* Read or write from an __iomem region (MMIO or I/O port) with an excluded
* range which is inaccessible. The excluded range drops writes and fills
@@ -44,15 +63,15 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf,
fillable = 0;
if (fillable >= 4 && !(off % 4)) {
- __le32 val;
+ u32 val;
if (iswrite) {
if (copy_from_user(&val, buf, 4))
return -EFAULT;
- iowrite32(le32_to_cpu(val), io + off);
+ vfio_iowrite32(val, io + off);
} else {
- val = cpu_to_le32(ioread32(io + off));
+ val = vfio_ioread32(io + off);
if (copy_to_user(buf, &val, 4))
return -EFAULT;
@@ -60,15 +79,15 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf,
filled = 4;
} else if (fillable >= 2 && !(off % 2)) {
- __le16 val;
+ u16 val;
if (iswrite) {
if (copy_from_user(&val, buf, 2))
return -EFAULT;
- iowrite16(le16_to_cpu(val), io + off);
+ vfio_iowrite16(val, io + off);
} else {
- val = cpu_to_le16(ioread16(io + off));
+ val = vfio_ioread16(io + off);
if (copy_to_user(buf, &val, 2))
return -EFAULT;
@@ -82,9 +101,9 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf,
if (copy_from_user(&val, buf, 1))
return -EFAULT;
- iowrite8(val, io + off);
+ vfio_iowrite8(val, io + off);
} else {
- val = ioread8(io + off);
+ val = vfio_ioread8(io + off);
if (copy_to_user(buf, &val, 1))
return -EFAULT;
@@ -113,6 +132,30 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf,
return done;
}
+static int vfio_pci_setup_barmap(struct vfio_pci_device *vdev, int bar)
+{
+ struct pci_dev *pdev = vdev->pdev;
+ int ret;
+ void __iomem *io;
+
+ if (vdev->barmap[bar])
+ return 0;
+
+ ret = pci_request_selected_regions(pdev, 1 << bar, "vfio");
+ if (ret)
+ return ret;
+
+ io = pci_iomap(pdev, bar, 0);
+ if (!io) {
+ pci_release_selected_regions(pdev, 1 << bar);
+ return -ENOMEM;
+ }
+
+ vdev->barmap[bar] = io;
+
+ return 0;
+}
+
ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
size_t count, loff_t *ppos, bool iswrite)
{
@@ -147,22 +190,13 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
if (!io)
return -ENOMEM;
x_end = end;
- } else if (!vdev->barmap[bar]) {
- int ret;
-
- ret = pci_request_selected_regions(pdev, 1 << bar, "vfio");
+ } else {
+ int ret = vfio_pci_setup_barmap(vdev, bar);
if (ret)
return ret;
- io = pci_iomap(pdev, bar, 0);
- if (!io) {
- pci_release_selected_regions(pdev, 1 << bar);
- return -ENOMEM;
- }
-
- vdev->barmap[bar] = io;
- } else
io = vdev->barmap[bar];
+ }
if (bar == vdev->msix_bar) {
x_start = vdev->msix_offset;
@@ -242,3 +276,113 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
return done;
}
+
+static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
+{
+ struct vfio_pci_ioeventfd *ioeventfd = opaque;
+
+ switch (ioeventfd->count) {
+ case 1:
+ vfio_iowrite8(ioeventfd->data, ioeventfd->addr);
+ break;
+ case 2:
+ vfio_iowrite16(ioeventfd->data, ioeventfd->addr);
+ break;
+ case 4:
+ vfio_iowrite32(ioeventfd->data, ioeventfd->addr);
+ break;
+#ifdef iowrite64
+ case 8:
+ vfio_iowrite64(ioeventfd->data, ioeventfd->addr);
+ break;
+#endif
+ }
+
+ return 0;
+}
+
+long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
+ uint64_t data, int count, int fd)
+{
+ struct pci_dev *pdev = vdev->pdev;
+ loff_t pos = offset & VFIO_PCI_OFFSET_MASK;
+ int ret, bar = VFIO_PCI_OFFSET_TO_INDEX(offset);
+ struct vfio_pci_ioeventfd *ioeventfd;
+
+ /* Only support ioeventfds into BARs */
+ if (bar > VFIO_PCI_BAR5_REGION_INDEX)
+ return -EINVAL;
+
+ if (pos + count > pci_resource_len(pdev, bar))
+ return -EINVAL;
+
+ /* Disallow ioeventfds working around MSI-X table writes */
+ if (bar == vdev->msix_bar &&
+ !(pos + count <= vdev->msix_offset ||
+ pos >= vdev->msix_offset + vdev->msix_size))
+ return -EINVAL;
+
+#ifndef iowrite64
+ if (count == 8)
+ return -EINVAL;
+#endif
+
+ ret = vfio_pci_setup_barmap(vdev, bar);
+ if (ret)
+ return ret;
+
+ mutex_lock(&vdev->ioeventfds_lock);
+
+ list_for_each_entry(ioeventfd, &vdev->ioeventfds_list, next) {
+ if (ioeventfd->pos == pos && ioeventfd->bar == bar &&
+ ioeventfd->data == data && ioeventfd->count == count) {
+ if (fd == -1) {
+ vfio_virqfd_disable(&ioeventfd->virqfd);
+ list_del(&ioeventfd->next);
+ vdev->ioeventfds_nr--;
+ kfree(ioeventfd);
+ ret = 0;
+ } else
+ ret = -EEXIST;
+
+ goto out_unlock;
+ }
+ }
+
+ if (fd < 0) {
+ ret = -ENODEV;
+ goto out_unlock;
+ }
+
+ if (vdev->ioeventfds_nr >= VFIO_PCI_IOEVENTFD_MAX) {
+ ret = -ENOSPC;
+ goto out_unlock;
+ }
+
+ ioeventfd = kzalloc(sizeof(*ioeventfd), GFP_KERNEL);
+ if (!ioeventfd) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ ioeventfd->addr = vdev->barmap[bar] + pos;
+ ioeventfd->data = data;
+ ioeventfd->pos = pos;
+ ioeventfd->bar = bar;
+ ioeventfd->count = count;
+
+ ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler,
+ NULL, NULL, &ioeventfd->virqfd, fd);
+ if (ret) {
+ kfree(ioeventfd);
+ goto out_unlock;
+ }
+
+ list_add(&ioeventfd->next, &vdev->ioeventfds_list);
+ vdev->ioeventfds_nr++;
+
+out_unlock:
+ mutex_unlock(&vdev->ioeventfds_lock);
+
+ return ret;
+}
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 45657e2b1ff7..5c212bf29640 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -102,6 +102,13 @@ struct vfio_pfn {
atomic_t ref_count;
};
+struct vfio_regions {
+ struct list_head list;
+ dma_addr_t iova;
+ phys_addr_t phys;
+ size_t len;
+};
+
#define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \
(!list_empty(&iommu->domain_list))
@@ -397,7 +404,6 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
{
unsigned long pfn = 0;
long ret, pinned = 0, lock_acct = 0;
- bool rsvd;
dma_addr_t iova = vaddr - dma->vaddr + dma->iova;
/* This code path is only user initiated */
@@ -408,14 +414,23 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret)
return ret;
+ if (is_invalid_reserved_pfn(*pfn_base)) {
+ struct vm_area_struct *vma;
+
+ down_read(&current->mm->mmap_sem);
+ vma = find_vma_intersection(current->mm, vaddr, vaddr + 1);
+ pinned = min_t(long, npage, vma_pages(vma));
+ up_read(&current->mm->mmap_sem);
+ return pinned;
+ }
+
pinned++;
- rsvd = is_invalid_reserved_pfn(*pfn_base);
/*
* Reserved pages aren't counted against the user, externally pinned
* pages are already counted against the user.
*/
- if (!rsvd && !vfio_find_vpfn(dma, iova)) {
+ if (!vfio_find_vpfn(dma, iova)) {
if (!lock_cap && current->mm->locked_vm + 1 > limit) {
put_pfn(*pfn_base, dma->prot);
pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
@@ -435,13 +450,12 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
if (ret)
break;
- if (pfn != *pfn_base + pinned ||
- rsvd != is_invalid_reserved_pfn(pfn)) {
+ if (pfn != *pfn_base + pinned) {
put_pfn(pfn, dma->prot);
break;
}
- if (!rsvd && !vfio_find_vpfn(dma, iova)) {
+ if (!vfio_find_vpfn(dma, iova)) {
if (!lock_cap &&
current->mm->locked_vm + lock_acct + 1 > limit) {
put_pfn(pfn, dma->prot);
@@ -459,10 +473,8 @@ out:
unpin_out:
if (ret) {
- if (!rsvd) {
- for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
- put_pfn(pfn, dma->prot);
- }
+ for (pfn = *pfn_base ; pinned ; pfn++, pinned--)
+ put_pfn(pfn, dma->prot);
return ret;
}
@@ -660,11 +672,102 @@ unpin_exit:
return i > npage ? npage : (i > 0 ? i : -EINVAL);
}
+static long vfio_sync_unpin(struct vfio_dma *dma, struct vfio_domain *domain,
+ struct list_head *regions)
+{
+ long unlocked = 0;
+ struct vfio_regions *entry, *next;
+
+ iommu_tlb_sync(domain->domain);
+
+ list_for_each_entry_safe(entry, next, regions, list) {
+ unlocked += vfio_unpin_pages_remote(dma,
+ entry->iova,
+ entry->phys >> PAGE_SHIFT,
+ entry->len >> PAGE_SHIFT,
+ false);
+ list_del(&entry->list);
+ kfree(entry);
+ }
+
+ cond_resched();
+
+ return unlocked;
+}
+
+/*
+ * Generally, VFIO needs to unpin remote pages after each IOTLB flush.
+ * Therefore, when using IOTLB flush sync interface, VFIO need to keep track
+ * of these regions (currently using a list).
+ *
+ * This value specifies maximum number of regions for each IOTLB flush sync.
+ */
+#define VFIO_IOMMU_TLB_SYNC_MAX 512
+
+static size_t unmap_unpin_fast(struct vfio_domain *domain,
+ struct vfio_dma *dma, dma_addr_t *iova,
+ size_t len, phys_addr_t phys, long *unlocked,
+ struct list_head *unmapped_list,
+ int *unmapped_cnt)
+{
+ size_t unmapped = 0;
+ struct vfio_regions *entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+
+ if (entry) {
+ unmapped = iommu_unmap_fast(domain->domain, *iova, len);
+
+ if (!unmapped) {
+ kfree(entry);
+ } else {
+ iommu_tlb_range_add(domain->domain, *iova, unmapped);
+ entry->iova = *iova;
+ entry->phys = phys;
+ entry->len = unmapped;
+ list_add_tail(&entry->list, unmapped_list);
+
+ *iova += unmapped;
+ (*unmapped_cnt)++;
+ }
+ }
+
+ /*
+ * Sync if the number of fast-unmap regions hits the limit
+ * or in case of errors.
+ */
+ if (*unmapped_cnt >= VFIO_IOMMU_TLB_SYNC_MAX || !unmapped) {
+ *unlocked += vfio_sync_unpin(dma, domain,
+ unmapped_list);
+ *unmapped_cnt = 0;
+ }
+
+ return unmapped;
+}
+
+static size_t unmap_unpin_slow(struct vfio_domain *domain,
+ struct vfio_dma *dma, dma_addr_t *iova,
+ size_t len, phys_addr_t phys,
+ long *unlocked)
+{
+ size_t unmapped = iommu_unmap(domain->domain, *iova, len);
+
+ if (unmapped) {
+ *unlocked += vfio_unpin_pages_remote(dma, *iova,
+ phys >> PAGE_SHIFT,
+ unmapped >> PAGE_SHIFT,
+ false);
+ *iova += unmapped;
+ cond_resched();
+ }
+ return unmapped;
+}
+
static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
bool do_accounting)
{
dma_addr_t iova = dma->iova, end = dma->iova + dma->size;
struct vfio_domain *domain, *d;
+ LIST_HEAD(unmapped_region_list);
+ int unmapped_region_cnt = 0;
long unlocked = 0;
if (!dma->size)
@@ -710,20 +813,26 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
break;
}
- unmapped = iommu_unmap(domain->domain, iova, len);
- if (WARN_ON(!unmapped))
- break;
-
- unlocked += vfio_unpin_pages_remote(dma, iova,
- phys >> PAGE_SHIFT,
- unmapped >> PAGE_SHIFT,
- false);
- iova += unmapped;
-
- cond_resched();
+ /*
+ * First, try to use fast unmap/unpin. In case of failure,
+ * switch to slow unmap/unpin path.
+ */
+ unmapped = unmap_unpin_fast(domain, dma, &iova, len, phys,
+ &unlocked, &unmapped_region_list,
+ &unmapped_region_cnt);
+ if (!unmapped) {
+ unmapped = unmap_unpin_slow(domain, dma, &iova, len,
+ phys, &unlocked);
+ if (WARN_ON(!unmapped))
+ break;
+ }
}
dma->iommu_mapped = false;
+
+ if (unmapped_region_cnt)
+ unlocked += vfio_sync_unpin(dma, domain, &unmapped_region_list);
+
if (do_accounting) {
vfio_lock_acct(dma->task, -unlocked, NULL);
return 0;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index c74372163ed2..1aa7b82e8169 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -575,6 +575,33 @@ struct vfio_device_gfx_plane_info {
#define VFIO_DEVICE_GET_GFX_DMABUF _IO(VFIO_TYPE, VFIO_BASE + 15)
+/**
+ * VFIO_DEVICE_IOEVENTFD - _IOW(VFIO_TYPE, VFIO_BASE + 16,
+ * struct vfio_device_ioeventfd)
+ *
+ * Perform a write to the device at the specified device fd offset, with
+ * the specified data and width when the provided eventfd is triggered.
+ * vfio bus drivers may not support this for all regions, for all widths,
+ * or at all. vfio-pci currently only enables support for BAR regions,
+ * excluding the MSI-X vector table.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+struct vfio_device_ioeventfd {
+ __u32 argsz;
+ __u32 flags;
+#define VFIO_DEVICE_IOEVENTFD_8 (1 << 0) /* 1-byte write */
+#define VFIO_DEVICE_IOEVENTFD_16 (1 << 1) /* 2-byte write */
+#define VFIO_DEVICE_IOEVENTFD_32 (1 << 2) /* 4-byte write */
+#define VFIO_DEVICE_IOEVENTFD_64 (1 << 3) /* 8-byte write */
+#define VFIO_DEVICE_IOEVENTFD_SIZE_MASK (0xf)
+ __u64 offset; /* device fd offset of write */
+ __u64 data; /* data to be written */
+ __s32 fd; /* -1 for de-assignment */
+};
+
+#define VFIO_DEVICE_IOEVENTFD _IO(VFIO_TYPE, VFIO_BASE + 16)
+
/* -------- API for Type1 VFIO IOMMU -------- */
/**
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 09f255bdf3ac..7abb79d8313d 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -534,7 +534,7 @@ static void handle_bar_read(unsigned int index, struct mdev_state *mdev_state,
/* Interrupt priority 2: Fifo trigger level reached */
if ((ier & UART_IER_RDI) &&
- (mdev_state->s[index].rxtx.count ==
+ (mdev_state->s[index].rxtx.count >=
mdev_state->s[index].intr_trigger_level))
*buf |= UART_IIR_RDI;