[PATCH v3] xen/x86/pvh: handle ACPI RSDT table in PVH Dom0 build

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

From: Stefano Stabellini <stefano.stabellini@xxxxxxx>

Xen always generates as XSDT table even if the firmware provided an RSDT table.
Copy the RSDT header from the firmware table, adjusting the signature, for the
XSDT table when not provided by the firmware.

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

This patch is used for development and testing of hyperlaunch using the QEMU
emulator. After dicussiong with Stefano, he was okay with me addressing Jan's
comment regarding the table signature and reposting for acceptance.

Changes in v3:
- ensure the constructed XSDT table always has the correct signature

---
 xen/arch/x86/hvm/dom0_build.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index ac71d43a6b3f..781aac00fe72 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -1077,7 +1077,16 @@ 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 )
@@ -1089,6 +1098,9 @@ static int __init pvh_setup_acpi_xsdt(struct domain *d, 
paddr_t madt_addr,
     xsdt->header = *table;
     acpi_os_unmap_memory(table, sizeof(*table));
 
+    /* In case the header is an RSDT copy, blindly ensure it has an XSDT sig */
+    xsdt->header.signature[0] = 'X';
+
     /* Add the custom MADT. */
     xsdt->table_offset_entry[0] = madt_addr;
 
-- 
2.30.2