On Tue, Jun 09, 2026 at 11:02:56AM +0200, Stefano Garzarella wrote:
On Mon, Jun 08, 2026 at 05:40:21PM +0200, Luigi Leonardi wrote:
On Mon, Jun 08, 2026 at 04:50:02PM +0200, Stefano Garzarella wrote:
On Mon, Jun 08, 2026 at 11:37:47AM +0200, Luigi Leonardi wrote:
Coconut SVSM, with the upcoming device tree support[1], will use
the IGVM device tree parameter to discover virtio-mmio and ISA serial
devices instead of relying on the fw_cfg interface, which is
QEMU-specific.
The IGVM parameter handler is implemented for the i386 machine
target and stubbed for all others.
[1] https://github.com/coconut-svsm/svsm/pull/1006
Signed-off-by: Luigi Leonardi <[email protected]>
---
backends/igvm.c | 2 ++
include/system/igvm.h | 2 ++
stubs/igvm.c | 6 ++++++
target/i386/igvm.c | 36 ++++++++++++++++++++++++++++++++++++
4 files changed, 46 insertions(+)
diff --git a/backends/igvm.c b/backends/igvm.c
index c347d0c17e..9c6bee4add 100644
--- a/backends/igvm.c
+++ b/backends/igvm.c
@@ -130,6 +130,8 @@ static struct QIGVMHandler handlers[] = {
qigvm_initialization_guest_policy },
{ IGVM_VHT_MADT, IGVM_HEADER_SECTION_DIRECTIVE,
qigvm_directive_madt },
+ { IGVM_VHT_DEVICE_TREE, IGVM_HEADER_SECTION_DIRECTIVE,
+ qigvm_directive_device_tree },
};
static int qigvm_handler(QIgvm *ctx, uint32_t type, Error **errp)
diff --git a/include/system/igvm.h b/include/system/igvm.h
index 64d3542311..d39f3d55f1 100644
--- a/include/system/igvm.h
+++ b/include/system/igvm.h
@@ -32,5 +32,7 @@ int qigvm_x86_set_vp_context(void *data, int index,
* IGVM parameter handlers
*/
int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data, Error **errp);
+int qigvm_directive_device_tree(QIgvm *ctx, const uint8_t *header_data,
+ Error **errp);
#endif
diff --git a/stubs/igvm.c b/stubs/igvm.c
index 9e9f683fc9..b4d533ad24 100644
--- a/stubs/igvm.c
+++ b/stubs/igvm.c
@@ -29,3 +29,9 @@ int qigvm_directive_madt(QIgvm *ctx, const uint8_t
*header_data, Error **errp)
{
return -1;
}
+
+int qigvm_directive_device_tree(QIgvm *ctx, const uint8_t *header_data,
+ Error **errp)
+{
+ return -1;
This is pre-existing in the other stubs, so maybe should be fixed
in another patch, but IMO we should set errp, like we do in other
files in stubs/ (e.g. monitor-internal.c, qmp*.c, etc.)
I mean something like:
error_setg(errp, "IGVM not supported on this platform");
Yep, I will send another patch.
+}
diff --git a/target/i386/igvm.c b/target/i386/igvm.c
index f41b498b89..13db6e9be0 100644
--- a/target/i386/igvm.c
+++ b/target/i386/igvm.c
@@ -11,6 +11,8 @@
#include "qemu/osdep.h"
+#include <libfdt.h>
+
#include "cpu.h"
#include "hw/i386/e820_memory_layout.h"
#include "hw/i386/acpi-build.h"
@@ -210,3 +212,37 @@ int qigvm_directive_madt(QIgvm *ctx, const uint8_t
*header_data, Error **errp)
g_array_free(madt, true);
return result;
}
+
+/*
+ * Process device tree IGVM parameter
+ */
+int qigvm_directive_device_tree(QIgvm *ctx, const uint8_t *header_data,
+ Error **errp)
+{
+ const IGVM_VHS_PARAMETER *param = (const IGVM_VHS_PARAMETER *)header_data;
+ QIgvmParameterData *param_entry;
+ uint32_t fdt_size;
+
+ /* Find the parameter area that should hold the device tree data */
This comment is a bit pointless; IMHO, we should explain why we
return success if we can't find the device tree area.
Good point: in every place where we used `qigvm_find_param_entry` we
have this behaviour. I don't think it makes too much sense because it's
probably due to a malformed igvm-file. WDYT?
ehm, I thought it was more about backward compatibility. For example,
QEMU supports the device-tree property, but the IGVM file (which is
probably outdated) doesn't have the entry because it's an old version,
so we don't return an error (though qigvm_find_param_entry() will
still print a warning, as it should). Or am I missing something?
In an "old" igvm file, where the device tree directive is not set,
`qigvm_directive_device_tree` will never run. Therefore backward
compatibility is guaranteed.
About `qigvm_find_param_entry()`, maybe Oliver can help us, as he
introduced that helper.
Luigi
