[Xen-changelog] [qemu-xen master] vfio: Add support for mmapping sub-page MMIO BARs

[patchbot@xxxxxxx]

commit 95251725e335af2b885e2ab33dd29c86f8084663
Author:     Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon Oct 31 09:53:04 2016 -0600
Commit:     Alex Williamson <alex.williamson@xxxxxxxxxx>
CommitDate: Mon Oct 31 09:53:04 2016 -0600

    vfio: Add support for mmapping sub-page MMIO BARs
    
    Now the kernel commit 05f0c03fbac1 ("vfio-pci: Allow to mmap
    sub-page MMIO BARs if the mmio page is exclusive") allows VFIO
    to mmap sub-page BARs. This is the corresponding QEMU patch.
    With those patches applied, we could passthrough sub-page BARs
    to guest, which can help to improve IO performance for some devices.
    
    In this patch, we expand MemoryRegions of these sub-page
    MMIO BARs to PAGE_SIZE in vfio_pci_write_config(), so that
    the BARs could be passed to KVM ioctl KVM_SET_USER_MEMORY_REGION
    with a valid size. The expanding size will be recovered when
    the base address of sub-page BAR is changed and not page aligned
    any more in guest. And we also set the priority of these BARs'
    memory regions to zero in case of overlap with BARs which share
    the same page with sub-page BARs in guest.
    
    Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
    Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
 hw/vfio/common.c |  3 +--
 hw/vfio/pci.c    | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index f528309..801578b 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -670,8 +670,7 @@ int vfio_region_setup(Object *obj, VFIODevice *vbasedev, 
VFIORegion *region,
                               region, name, region->size);
 
         if (!vbasedev->no_mmap &&
-            region->flags & VFIO_REGION_INFO_FLAG_MMAP &&
-            !(region->size & ~qemu_real_host_page_mask)) {
+            region->flags & VFIO_REGION_INFO_FLAG_MMAP) {
 
             ret = vfio_setup_region_sparse_mmaps(region, info);
 
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index b399742..d7dbe0e 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1071,6 +1071,55 @@ static const MemoryRegionOps vfio_vga_ops = {
 };
 
 /*
+ * Expand memory region of sub-page(size < PAGE_SIZE) MMIO BAR to page
+ * size if the BAR is in an exclusive page in host so that we could map
+ * this BAR to guest. But this sub-page BAR may not occupy an exclusive
+ * page in guest. So we should set the priority of the expanded memory
+ * region to zero in case of overlap with BARs which share the same page
+ * with the sub-page BAR in guest. Besides, we should also recover the
+ * size of this sub-page BAR when its base address is changed in guest
+ * and not page aligned any more.
+ */
+static void vfio_sub_page_bar_update_mapping(PCIDevice *pdev, int bar)
+{
+    VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
+    VFIORegion *region = &vdev->bars[bar].region;
+    MemoryRegion *mmap_mr, *mr;
+    PCIIORegion *r;
+    pcibus_t bar_addr;
+    uint64_t size = region->size;
+
+    /* Make sure that the whole region is allowed to be mmapped */
+    if (region->nr_mmaps != 1 || !region->mmaps[0].mmap ||
+        region->mmaps[0].size != region->size) {
+        return;
+    }
+
+    r = &pdev->io_regions[bar];
+    bar_addr = r->addr;
+    mr = region->mem;
+    mmap_mr = &region->mmaps[0].mem;
+
+    /* If BAR is mapped and page aligned, update to fill PAGE_SIZE */
+    if (bar_addr != PCI_BAR_UNMAPPED &&
+        !(bar_addr & ~qemu_real_host_page_mask)) {
+        size = qemu_real_host_page_size;
+    }
+
+    memory_region_transaction_begin();
+
+    memory_region_set_size(mr, size);
+    memory_region_set_size(mmap_mr, size);
+    if (size != region->size && memory_region_is_mapped(mr)) {
+        memory_region_del_subregion(r->address_space, mr);
+        memory_region_add_subregion_overlap(r->address_space,
+                                            bar_addr, mr, 0);
+    }
+
+    memory_region_transaction_commit();
+}
+
+/*
  * PCI config space
  */
 uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len)
@@ -1153,6 +1202,24 @@ void vfio_pci_write_config(PCIDevice *pdev,
         } else if (was_enabled && !is_enabled) {
             vfio_msix_disable(vdev);
         }
+    } else if (ranges_overlap(addr, len, PCI_BASE_ADDRESS_0, 24) ||
+        range_covers_byte(addr, len, PCI_COMMAND)) {
+        pcibus_t old_addr[PCI_NUM_REGIONS - 1];
+        int bar;
+
+        for (bar = 0; bar < PCI_ROM_SLOT; bar++) {
+            old_addr[bar] = pdev->io_regions[bar].addr;
+        }
+
+        pci_default_write_config(pdev, addr, val, len);
+
+        for (bar = 0; bar < PCI_ROM_SLOT; bar++) {
+            if (old_addr[bar] != pdev->io_regions[bar].addr &&
+                pdev->io_regions[bar].size > 0 &&
+                pdev->io_regions[bar].size < qemu_real_host_page_size) {
+                vfio_sub_page_bar_update_mapping(pdev, bar);
+            }
+        }
     } else {
         /* Write everything to QEMU to keep emulated bits correct */
         pci_default_write_config(pdev, addr, val, len);
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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