The MMIO region size required to support virtualized environments with
large PCI BAR regions can exceed the hardcoded limit configured in QEMU.
For example, a VM with multiple NVIDIA Grace-Hopper GPUs passed through
requires more MMIO memory than the amount provided by VIRT_HIGH_PCIE_MMIO
(currently 512GB). Instead of updating VIRT_HIGH_PCIE_MMIO, introduce a
new parameter, highmem-mmio-size, that specifies the MMIO size required
to support the VM configuration.
Example usage with 1TB MMIO region size:
-machine virt,gic-version=3,highmem-mmio-size=1T
Signed-off-by: Matthew R. Ochs <mo...@nvidia.com>
Reviewed-by: Gavin Shan <gs...@redhat.com>
Reviewed-by: Shameer Kolothum <shameerali.kolothum.th...@huawei.com>
Reviewed-by: Eric Auger <eric.au...@redhat.com>
Reviewed-by: Nicolin Chen <nicol...@nvidia.com>
---
v6: - Fixed minor coding style nit
v5: - Removed hyphens from power of 2
- Consistently use property name in all error messages
- Use #defines for default high PCIE MMIO size
- Use size_to_str() when printing size values
- Add comment clarifying that highmem-mmio-size will
update the corresponding value in extended_memmap
v4: - Added default size to highmem-mmio-size description
v3: - Updated highmem-mmio-size description
v2: - Add unit suffix to example in commit message
- Use existing "high memory region" terminology
- Resolve minor braces nit
docs/system/arm/virt.rst | 4 ++++
hw/arm/virt.c | 52 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 55 insertions(+), 1 deletion(-)
diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst
index 0c9c2ce0351c..adf446c0a295 100644
--- a/docs/system/arm/virt.rst
+++ b/docs/system/arm/virt.rst
@@ -144,6 +144,10 @@ highmem-mmio
Set ``on``/``off`` to enable/disable the high memory region for PCI MMIO.
The default is ``on``.
+highmem-mmio-size
+ Set the high memory region size for PCI MMIO. Must be a power of 2 and
+ greater than or equal to the default size (512G).
+
gic-version
Specify the version of the Generic Interrupt Controller (GIC) to provide.
Valid values are:
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 4a5a9666e916..ee69081ef421 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -53,6 +53,7 @@
#include "hw/loader.h"
#include "qapi/error.h"
#include "qemu/bitops.h"
+#include "qemu/cutils.h"
#include "qemu/error-report.h"
#include "qemu/module.h"
#include "hw/pci-host/gpex.h"
@@ -192,6 +193,10 @@ static const MemMapEntry base_memmap[] = {
[VIRT_MEM] = { GiB, LEGACY_RAMLIMIT_BYTES },
};
+/* Update the docs for highmem-mmio-size when changing this default */
+#define DEFAULT_HIGH_PCIE_MMIO_SIZE_GB 512
+#define DEFAULT_HIGH_PCIE_MMIO_SIZE (DEFAULT_HIGH_PCIE_MMIO_SIZE_GB * GiB)
+
/*
* Highmem IO Regions: This memory map is floating, located after the RAM.
* Each MemMapEntry base (GPA) will be dynamically computed, depending on the
@@ -207,13 +212,16 @@ static const MemMapEntry base_memmap[] = {
* PA space for one specific region is always reserved, even if the region
* has been disabled or doesn't fit into the PA space. However, the PA space
* for the region won't be reserved in these circumstances with compact layout.
+ *
+ * Note that the highmem-mmio-size property will update the high PCIE MMIO size
+ * field in this array.
*/
static MemMapEntry extended_memmap[] = {
/* Additional 64 MB redist region (can contain up to 512 redistributors) */
[VIRT_HIGH_GIC_REDIST2] = { 0x0, 64 * MiB },
[VIRT_HIGH_PCIE_ECAM] = { 0x0, 256 * MiB },
/* Second PCIe window */
- [VIRT_HIGH_PCIE_MMIO] = { 0x0, 512 * GiB },
+ [VIRT_HIGH_PCIE_MMIO] = { 0x0, DEFAULT_HIGH_PCIE_MMIO_SIZE },
};
static const int a15irqmap[] = {
@@ -2550,6 +2558,40 @@ static void virt_set_highmem_mmio(Object *obj, bool
value, Error **errp)
vms->highmem_mmio = value;
}
+static void virt_get_highmem_mmio_size(Object *obj, Visitor *v,
+ const char *name, void *opaque,
+ Error **errp)
+{
+ uint64_t size = extended_memmap[VIRT_HIGH_PCIE_MMIO].size;
+
+ visit_type_size(v, name, &size, errp);
+}
+
+static void virt_set_highmem_mmio_size(Object *obj, Visitor *v,
+ const char *name, void *opaque,
+ Error **errp)
+{
+ uint64_t size;
+
+ if (!visit_type_size(v, name, &size, errp)) {
+ return;
+ }
+
+ if (!is_power_of_2(size)) {
+ error_setg(errp, "highmem-mmio-size is not a power of 2");
+ return;
+ }
+
+ if (size < DEFAULT_HIGH_PCIE_MMIO_SIZE) {
+ char *sz = size_to_str(DEFAULT_HIGH_PCIE_MMIO_SIZE);
+ error_setg(errp, "highmem-mmio-size cannot be set to a lower value "
+ "than the default (%s)", sz);
+ g_free(sz);
+ return;
+ }
+
+ extended_memmap[VIRT_HIGH_PCIE_MMIO].size = size;
+}
static bool virt_get_its(Object *obj, Error **errp)
{
@@ -3207,6 +3249,14 @@ static void virt_machine_class_init(ObjectClass *oc,
void *data)
"Set on/off to enable/disable high "
"memory region for PCI MMIO");
+ object_class_property_add(oc, "highmem-mmio-size", "size",
+ virt_get_highmem_mmio_size,
+ virt_set_highmem_mmio_size,
+ NULL, NULL);
+ object_class_property_set_description(oc, "highmem-mmio-size",
+ "Set the high memory region size "
+ "for PCI MMIO");
+
object_class_property_add_str(oc, "gic-version", virt_get_gic_version,
virt_set_gic_version);
object_class_property_set_description(oc, "gic-version",
--
2.46.0
