[PATCH v2] xen/x86/pvh: handle ACPI RSDT table in PVH Dom0 build

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Stefano Stabellini <stefano.stabellini@xxxxxxx>

Xen always generates a XSDT table even if the firmware provided a RSDT
table. Copy the RSDT header from the firmware table when the XSDT table
is missing.

Fixes: 1d74282c455f ('x86: setup PVHv2 Dom0 ACPI tables')
Suggested-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
---

Note that this patch is sufficient to get Xen and Dom0 PVH to boot on
QEMU. It turns out that dom0-iommu=none is not needed because QEMU can
actually emulate an AMD IOMMU. I just needed to use the right command
line arguments. Without dom0-iommu=none, the error fixed by the second
patch in v1 doesn't manifest, so I dropped patch 2/2.

FYI this is the QEMU command line to use:

qemu-system-x86_64 \
    -machine q35 \
    -device amd-iommu \
    -m 2G -smp 2 \
    -monitor none -serial stdio \
    -nographic \
    -device virtio-net-pci,netdev=n0 \
    -netdev user,id=n0,tftp=binaries,bootfile=/pxelinux.0

This is pxelinux.0:

kernel xen console=com1 dom0=pvh dom0_mem=1G noreboot
module bzImage console=hvc0
module xen-rootfs.cpio.gz
boot

I'll work on adding a gitlab-ci test for this next.

---
 xen/arch/x86/hvm/dom0_build.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index fd2cbf68bc..e1043e40d2 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -966,7 +966,16 @@ static int __init pvh_setup_acpi_xsdt(struct domain *d, 
paddr_t madt_addr,
         rc = -EINVAL;
         goto out;
     }
-    xsdt_paddr = rsdp->xsdt_physical_address;
+    /*
+     * Note the header is the same for both RSDT and XSDT, so it's fine to
+     * copy the native RSDT header to the Xen crafted XSDT if no native
+     * XSDT is available.
+     */
+    if ( rsdp->revision > 1 && rsdp->xsdt_physical_address )
+        xsdt_paddr = rsdp->xsdt_physical_address;
+    else
+        xsdt_paddr = rsdp->rsdt_physical_address;
+
     acpi_os_unmap_memory(rsdp, sizeof(*rsdp));
     table = acpi_os_map_memory(xsdt_paddr, sizeof(*table));
     if ( !table )
-- 
2.25.1