On 10/27/2026 11:27 AM, Shameer Kolothum Thodi wrote:
>
>
>> -----Original Message-----
>> From: Tushar Dave <[email protected]>
>> Sent: 16 September 2026 19:56
>> To: [email protected]
>> Cc: [email protected]; [email protected]; [email protected];
>> [email protected]; [email protected]; Alex Williamson
>> <[email protected]>; Jason Gunthorpe <[email protected]>; Shameer
>> Kolothum Thodi <[email protected]>
>> Subject: [PATCH 5/5] hw/arm/virt: add highmem-mmio-base property
>>
>> Add a highmem-mmio-base property to override the base of the virt
>> machine's high PCIe MMIO window, alongside the existing
>> highmem-mmio-size:
>>
>> -machine virt,highmem-mmio-base=<addr>,highmem-mmio-size=<size>
>>
>> Some PCI devices require MMIO resources to be placed within a
>> specific address range that cannot be satisfied by the default
>> placement. The configured base is validated to be non-zero, aligned
>> to highmem-mmio-size, non-overlapping with the existing high memory
>> layout, and within the configured physical address space.
>>
>> Signed-off-by: Tushar Dave <[email protected]>
>> ---
>> hw/arm/virt.c | 62
>> ++++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 61 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index c5db663858..3a554dd26c 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -2513,9 +2513,34 @@ static void
>> virt_set_high_memmap(VirtMachineState *vms,
>>
>> for (i = VIRT_LOWMEMMAP_LAST; i < ARRAY_SIZE(extended_memmap);
>> i++) {
>> region_enabled = virt_get_high_memmap_enabled(vms, i);
>> - region_base = ROUND_UP(base, extended_memmap[i].size);
>> region_size = extended_memmap[i].size;
>>
>> + if (i == VIRT_HIGH_PCIE_MMIO && extended_memmap[i].base) {
>> + region_base = extended_memmap[i].base;
>> +
>> + if (region_base < base) {
>> + error_report("highmem-mmio-base 0x%"PRIx64" overlaps prior "
>> + "high memory layout (must be >= 0x%"PRIx64")",
>> + region_base, base);
>> + exit(1);
>> + }
>> + if (region_base % region_size != 0) {
>> + error_report("highmem-mmio-base 0x%"PRIx64" must be "
>> + "aligned to highmem-mmio-size 0x%"PRIx64,
>> + region_base, region_size);
>> + exit(1);
>> + }
>> + if (region_base + region_size > BIT_ULL(pa_bits)) {
>
> region_base + region_size can overflow and bypass this check.
Good catch. I will amend this in V2 with overflow check.
>
>> + error_report("highmem-mmio-base + highmem-mmio-size "
>> + "[0x%"PRIx64", 0x%"PRIx64") exceeds %d-bit PA "
>> + "space", region_base,
>> + region_base + region_size, pa_bits);
>> + exit(1);
>> + }
>> + } else {
>> + region_base = ROUND_UP(base, region_size);
>> + }
>> +
>> vms->memmap[i].base = region_base;
>> vms->memmap[i].size = region_size;
>>
>> @@ -3416,6 +3441,33 @@ static void virt_set_highmem_mmio_size(Object
>> *obj, Visitor *v,
>> extended_memmap[VIRT_HIGH_PCIE_MMIO].size = size;
>> }
>>
>> +static void virt_get_highmem_mmio_base(Object *obj, Visitor *v,
>> + const char *name, void *opaque,
>> + Error **errp)
>> +{
>> + uint64_t base = extended_memmap[VIRT_HIGH_PCIE_MMIO].base;
>> +
>> + visit_type_size(v, name, &base, errp);
>> +}
>> +
>> +static void virt_set_highmem_mmio_base(Object *obj, Visitor *v,
>> + const char *name, void *opaque,
>> + Error **errp)
>> +{
>> + uint64_t base;
>> +
>> + if (!visit_type_size(v, name, &base, errp)) {
>> + return;
>> + }
>> +
>> + if (base == 0) {
>> + error_setg(errp, "highmem-mmio-base cannot be 0");
>> + return;
>> + }
>> +
>> + extended_memmap[VIRT_HIGH_PCIE_MMIO].base = base;
>> +}
>> +
>> static char *virt_get_msi(Object *obj, Error **errp)
>> {
>> VirtMachineState *vms = VIRT_MACHINE(obj);
>> @@ -4286,6 +4338,14 @@ static void virt_machine_class_init(ObjectClass
>> *oc, const void *data)
>> "Set the high memory region size "
>> "for PCI MMIO");
>>
>> + object_class_property_add(oc, "highmem-mmio-base", "size",
>> + virt_get_highmem_mmio_base,
>> + virt_set_highmem_mmio_base,
>> + NULL, NULL);
>> + object_class_property_set_description(oc, "highmem-mmio-base",
>> + "Set the high memory region base "
>> + "for PCI MMIO");
>> +
>
> Add this to docs/system/arm/virt.rst as well.
Sure thing.
Thanks.
-Tushar
>
> Thanks,
> Shameer
