Re: [PATCH v3 08/10] hw/i386: Reserve AMD IOMMU HT GPA range for Hygon

On Mon, Aug 24, 2026 at 12:53:12PM +0800, Tina Zhang wrote:
> Date: Mon, 24 Aug 2026 12:53:12 +0800
> From: Tina Zhang <[email protected]>
> Subject: [PATCH v3 08/10] hw/i386: Reserve AMD IOMMU HT GPA range for Hygon
> X-Mailer: git-send-email 2.43.7
> 
> pc_memory_init() avoids the AMD IOMMU HyperTransport range below 1 TiB
> only for AMD vCPUs.  Dhyana therefore allows RAM, hotplug address space,
> or 64-bit PCI MMIO to overlap 0xfd00000000-0xffffffffff.
> 
> Linux supports Dhyana platforms in the AMD IOMMU driver.  The driver
> reports this range as reserved unless the IOMMU advertises
> FEATURE_HT_RANGE_IGNORE.  A VFIO device cannot DMA to guest addresses
> that QEMU places in the reserved range: VFIO_DMA_MAP may fail with
> -EINVAL, or the IOMMU may report an INVALID_DEVICE_REQUEST fault.
> 
> Apply the AMD IOMMU HT GPA layout to Hygon vCPUs.  When the possible
> address space reaches the reserved range, move RAM above 4 GiB to 1 TiB;
> also expose the range as reserved in E820 when the vCPU can address it.
> 
> Changing the GPA layout affects migration, so enable the Hygon behavior
> through x-hygon-vendor-abi-fixes.  pc-11.1 and older machine types retain
> their previous Hygon layout.  The existing enforce_amd_1tb_hole setting
> continues to preserve the AMD layout of pc/q35 machine types through 7.0.
> 
> Add functional tests for Dhyana with pc-q35-11.2 and with pc-q35-11.1
> compatibility.
> 
> Signed-off-by: Yanjing Zhou <[email protected]>
> Signed-off-by: Tina Zhang <[email protected]>
> ---
>  hw/i386/pc.c                                  | 26 ++++++++++----
>  .../functional/x86_64/test_mem_addr_space.py  | 36 +++++++++++++++++++
>  2 files changed, 55 insertions(+), 7 deletions(-)

Reviewed-by: Zhao Liu <[email protected]>