[PATCH v5 6/6] igvm: Fill MADT IGVM parameter field

[Oliver Steffen <osteffen@redhat.com>]

Use the new acpi_build_madt_standalone() function to fill the MADT
parameter field.

The IGVM parameter can be consumed by Coconut SVSM [1], instead of
relying on the fw_cfg interface, which has caused problems before due to
unexpected access [2,3]. Using IGVM parameters is the default way for
Coconut SVSM across hypervisors; switching over would allow removing
specialized code paths for QEMU in Coconut.

Coconut SVSM needs to know the SMP configuration, but does not look at
any other ACPI data, nor does it interact with the PCI bus settings.
Since the MADT is static and not linked with other ACPI tables, it can
be supplied stand-alone like this.

Generating the MADT twice (during ACPI table building and IGVM processing)
seems acceptable, since there is no infrastructure to obtain the MADT
out of the ACPI table memory area.

In any case OVMF, which runs after SVSM has already been initialized,
will continue reading all ACPI tables via fw_cfg and provide fixed up
ACPI data to the OS as before without any changes.

[1] https://github.com/coconut-svsm/svsm/pull/858
[2] https://gitlab.com/qemu-project/qemu/-/issues/2882
[3] https://github.com/coconut-svsm/svsm/issues/646

Signed-off-by: Oliver Steffen <osteffen@redhat.com>
---
 backends/igvm.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/backends/igvm.c b/backends/igvm.c
index f26eb633f8..1d8f807cf6 100644
--- a/backends/igvm.c
+++ b/backends/igvm.c
@@ -21,6 +21,7 @@
 #include "system/memory.h"
 #include "system/address-spaces.h"
 #include "hw/core/cpu.h"
+#include "hw/i386/acpi-build.h"
 
 #include "trace.h"
 
@@ -138,6 +139,8 @@ static int qigvm_directive_snp_id_block(QIgvm *ctx, const uint8_t *header_data,
 static int qigvm_initialization_guest_policy(QIgvm *ctx,
                                        const uint8_t *header_data,
                                        Error **errp);
+static int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data,
+                                Error **errp);
 
 struct QIGVMHandler {
     uint32_t type;
@@ -166,6 +169,8 @@ static struct QIGVMHandler handlers[] = {
       qigvm_directive_snp_id_block },
     { IGVM_VHT_GUEST_POLICY, IGVM_HEADER_SECTION_INITIALIZATION,
       qigvm_initialization_guest_policy },
+    { IGVM_VHT_MADT, IGVM_HEADER_SECTION_DIRECTIVE,
+      qigvm_directive_madt },
 };
 
 static int qigvm_handler(QIgvm *ctx, uint32_t type, Error **errp)
@@ -779,6 +784,34 @@ static int qigvm_initialization_guest_policy(QIgvm *ctx,
     return 0;
 }
 
+static int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data,
+                                Error **errp)
+{
+    const IGVM_VHS_PARAMETER *param = (const IGVM_VHS_PARAMETER *)header_data;
+    QIgvmParameterData *param_entry;
+    int result = 0;
+
+    /* Find the parameter area that should hold the MADT data */
+    param_entry = qigvm_find_param_entry(ctx, param->parameter_area_index);
+    if (param_entry == NULL) {
+        return 0;
+    }
+
+    GArray *madt = acpi_build_madt_standalone(ctx->machine_state);
+
+    if (madt->len <= param_entry->size) {
+        memcpy(param_entry->data, madt->data, madt->len);
+    } else {
+        error_setg(
+            errp,
+            "IGVM: MADT size exceeds parameter area defined in IGVM file");
+        result = -1;
+    }
+
+    g_array_free(madt, true);
+    return result;
+}
+
 static int qigvm_supported_platform_compat_mask(QIgvm *ctx, Error **errp)
 {
     int32_t header_count;
-- 
2.52.0