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vfio/common: Separate vfio-pci ranges
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QEMU computes the DMA logging ranges for two predefined ranges: 32-bit
and 64-bit. In the OVMF case, when the dynamic MMIO window is enabled,
QEMU includes in the 64-bit range the RAM regions at the lower part
and vfio-pci device RAM regions which are at the top of the address
space. This range contains a large gap and the size can be bigger than
the dirty tracking HW limits of some devices (MLX5 has a 2^42 limit).

To avoid such large ranges, introduce a new PCI range covering the
vfio-pci device RAM regions, this only if the addresses are above 4GB
to avoid breaking potential SeaBIOS guests.

[ clg: - wrote commit log
       - fixed overlapping 32-bit and PCI ranges when using SeaBIOS ]

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Fixes: 5255bbf ("vfio/common: Add device dirty page tracking start/stop")
Signed-off-by: Cédric Le Goater <clg@redhat.com>
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@jpemartins @legoater
jpemartins authored and legoater committed Sep 11, 2023
1 parent 6153797 commit a31fe5d
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Showing 2 changed files with 61 additions and 12 deletions.
71 changes: 60 additions & 11 deletions hw/vfio/common.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@

#include "hw/vfio/vfio-common.h"
#include "hw/vfio/vfio.h"
#include "hw/vfio/pci.h"
#include "exec/address-spaces.h"
#include "exec/memory.h"
#include "exec/ram_addr.h"
Expand Down Expand Up @@ -1400,6 +1401,8 @@ typedef struct VFIODirtyRanges {
hwaddr max32;
hwaddr min64;
hwaddr max64;
hwaddr minpci64;
hwaddr maxpci64;
} VFIODirtyRanges;

typedef struct VFIODirtyRangesListener {
Expand All @@ -1408,6 +1411,31 @@ typedef struct VFIODirtyRangesListener {
MemoryListener listener;
} VFIODirtyRangesListener;

static bool vfio_section_is_vfio_pci(MemoryRegionSection *section,
VFIOContainer *container)
{
VFIOPCIDevice *pcidev;
VFIODevice *vbasedev;
VFIOGroup *group;
Object *owner;

owner = memory_region_owner(section->mr);

QLIST_FOREACH(group, &container->group_list, container_next) {
QLIST_FOREACH(vbasedev, &group->device_list, next) {
if (vbasedev->type != VFIO_DEVICE_TYPE_PCI) {
continue;
}
pcidev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
if (OBJECT(pcidev) == owner) {
return true;
}
}
}

return false;
}

static void vfio_dirty_tracking_update(MemoryListener *listener,
MemoryRegionSection *section)
{
Expand All @@ -1424,19 +1452,32 @@ static void vfio_dirty_tracking_update(MemoryListener *listener,
}

/*
* The address space passed to the dirty tracker is reduced to two ranges:
* one for 32-bit DMA ranges, and another one for 64-bit DMA ranges.
* The address space passed to the dirty tracker is reduced to three ranges:
* one for 32-bit DMA ranges, one for 64-bit DMA ranges and one for the
* PCI 64-bit hole.
*
* The underlying reports of dirty will query a sub-interval of each of
* these ranges.
*
* The purpose of the dual range handling is to handle known cases of big
* holes in the address space, like the x86 AMD 1T hole. The alternative
* would be an IOVATree but that has a much bigger runtime overhead and
* unnecessary complexity.
* The purpose of the three range handling is to handle known cases of big
* holes in the address space, like the x86 AMD 1T hole, and firmware (like
* OVMF) which may relocate the pci-hole64 to the end of the address space.
* The latter would otherwise generate large ranges for tracking, stressing
* the limits of supported hardware. The pci-hole32 will always be below 4G
* (overlapping or not) so it doesn't need special handling and is part of
* the 32-bit range.
*
* The alternative would be an IOVATree but that has a much bigger runtime
* overhead and unnecessary complexity.
*/
min = (end <= UINT32_MAX) ? &range->min32 : &range->min64;
max = (end <= UINT32_MAX) ? &range->max32 : &range->max64;

if (vfio_section_is_vfio_pci(section, dirty->container) &&
iova >= UINT32_MAX) {
min = &range->minpci64;
max = &range->maxpci64;
} else {
min = (end <= UINT32_MAX) ? &range->min32 : &range->min64;
max = (end <= UINT32_MAX) ? &range->max32 : &range->max64;
}
if (*min > iova) {
*min = iova;
}
Expand All @@ -1461,6 +1502,7 @@ static void vfio_dirty_tracking_init(VFIOContainer *container,
memset(&dirty, 0, sizeof(dirty));
dirty.ranges.min32 = UINT32_MAX;
dirty.ranges.min64 = UINT64_MAX;
dirty.ranges.minpci64 = UINT64_MAX;
dirty.listener = vfio_dirty_tracking_listener;
dirty.container = container;

Expand Down Expand Up @@ -1531,7 +1573,8 @@ vfio_device_feature_dma_logging_start_create(VFIOContainer *container,
* DMA logging uAPI guarantees to support at least a number of ranges that
* fits into a single host kernel base page.
*/
control->num_ranges = !!tracking->max32 + !!tracking->max64;
control->num_ranges = !!tracking->max32 + !!tracking->max64 +
!!tracking->maxpci64;
ranges = g_try_new0(struct vfio_device_feature_dma_logging_range,
control->num_ranges);
if (!ranges) {
Expand All @@ -1550,11 +1593,17 @@ vfio_device_feature_dma_logging_start_create(VFIOContainer *container,
if (tracking->max64) {
ranges->iova = tracking->min64;
ranges->length = (tracking->max64 - tracking->min64) + 1;
ranges++;
}
if (tracking->maxpci64) {
ranges->iova = tracking->minpci64;
ranges->length = (tracking->maxpci64 - tracking->minpci64) + 1;
}

trace_vfio_device_dirty_tracking_start(control->num_ranges,
tracking->min32, tracking->max32,
tracking->min64, tracking->max64);
tracking->min64, tracking->max64,
tracking->minpci64, tracking->maxpci64);

return feature;
}
Expand Down
2 changes: 1 addition & 1 deletion hw/vfio/trace-events
View file
Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ vfio_known_safe_misalignment(const char *name, uint64_t iova, uint64_t offset_wi
vfio_listener_region_add_no_dma_map(const char *name, uint64_t iova, uint64_t size, uint64_t page_size) "Region \"%s\" 0x%"PRIx64" size=0x%"PRIx64" is not aligned to 0x%"PRIx64" and cannot be mapped for DMA"
vfio_listener_region_del(uint64_t start, uint64_t end) "region_del 0x%"PRIx64" - 0x%"PRIx64
vfio_device_dirty_tracking_update(uint64_t start, uint64_t end, uint64_t min, uint64_t max) "section 0x%"PRIx64" - 0x%"PRIx64" -> update [0x%"PRIx64" - 0x%"PRIx64"]"
vfio_device_dirty_tracking_start(int nr_ranges, uint64_t min32, uint64_t max32, uint64_t min64, uint64_t max64) "nr_ranges %d 32:[0x%"PRIx64" - 0x%"PRIx64"], 64:[0x%"PRIx64" - 0x%"PRIx64"]"
vfio_device_dirty_tracking_start(int nr_ranges, uint64_t min32, uint64_t max32, uint64_t min64, uint64_t max64, uint64_t minpci, uint64_t maxpci) "nr_ranges %d 32:[0x%"PRIx64" - 0x%"PRIx64"], 64:[0x%"PRIx64" - 0x%"PRIx64"], pci64:[0x%"PRIx64" - 0x%"PRIx64"]"
vfio_disconnect_container(int fd) "close container->fd=%d"
vfio_put_group(int fd) "close group->fd=%d"
vfio_get_device(const char * name, unsigned int flags, unsigned int num_regions, unsigned int num_irqs) "Device %s flags: %u, regions: %u, irqs: %u"
Expand Down

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