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igvm: Fill MADT IGVM parameter field on x86_64

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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.

The IGVM parameter handler is implemented for the i386 machine target
and stubbed for all others.

[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>
Message-ID: <20260130054714.715928-10-osteffen@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Oliver Steffen
2026-01-30 06:47:14 +01:00
committed by Gerd Hoffmann
parent 81553078a1
commit dea1f68a5c
4 changed files with 45 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
backends/igvm.c
View File

@@ -128,6 +128,8 @@ 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)

5
include/system/igvm-internal.h
View File

@@ -74,4 +74,9 @@ IgvmHandle qigvm_file_init(char *filename, Error **errp);
QIgvmParameterData*
qigvm_find_param_entry(QIgvm *igvm, uint32_t parameter_area_index);
/*
* IGVM parameter handlers
*/
int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data, Error **errp);
#endif

6
stubs/igvm.c
View File

@@ -12,6 +12,7 @@
#include "qemu/osdep.h"
#include "system/igvm.h"
#include "system/igvm-internal.h"
int qigvm_x86_get_mem_map_entry(int index,
ConfidentialGuestMemoryMapEntry *entry,
@@ -24,3 +25,8 @@ int qigvm_x86_set_vp_context(void *data, int index, Error **errp)
{
return -1;
}
int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data, Error **errp)
{
return -1;
}

32
target/i386/igvm.c
View File

@@ -13,7 +13,9 @@
#include "cpu.h"
#include "hw/i386/e820_memory_layout.h"
#include "hw/i386/acpi-build.h"
#include "system/igvm.h"
#include "system/igvm-internal.h"
struct IgvmNativeVpContextX64 {
uint64_t rax;
@@ -178,3 +180,33 @@ void qigvm_x86_bsp_reset(CPUX86State *env)
qigvm_x86_load_context(bsp_context, env);
}
/*
* Process MADT IGVM parameter
*/
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;
}