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hw/arm/virt: Support larger highmem MMIO regions

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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 <mochs@nvidia.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Message-id: 20250221145419.1281890-1-mochs@nvidia.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Matthew R. Ochs 2025-02-21 06:54:19 -08:00 committed by Peter Maydell
parent ab544de127
commit f10104aeae
2 changed files with 55 additions and 1 deletions
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4
docs/system/arm/virt.rst
View File

@ -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:

52
hw/arm/virt.c
View File

@ -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",