Normally, there is no need to perform firmware reconfiguration once the
virtual machine has started. Hence, currently ovmf firmware parsing happens only
once. However, if the firmware changes betweeen boots then reconfiguration needs
to happen again. Firmware can change if for example the guest brings its own
firmware bundle and installs it with the help of the hypervisor[1]. Therefore,
this change introduces a new api with which firmware configuration steps can
be forced again.
This is mostly refactoring work. No functional changes. CI pipeline does not
break with this change.

1) https://pretalx.com/kvm-forum-2024/talk/HJSKRQ/

Signed-off-by: Ani Sinha <anisinha@redhat.com>
---
 hw/i386/pc_sysfw.c            | 26 ++++++++++++++++++--------
 hw/i386/pc_sysfw_ovmf-stubs.c |  5 +++++
 hw/i386/pc_sysfw_ovmf.c       |  5 +++++
 include/hw/i386/pc.h          |  1 +
 include/hw/i386/x86.h         |  1 +
 5 files changed, 30 insertions(+), 8 deletions(-)

changelog:
v3 function name change to invalidate_ovmf_parsed_metadata()
v2: Gerd's suggestion to add a new function to set ovmf_flash_parsed to
false added.

diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
index 1eeb58ab37..a9943d95c8 100644
--- a/hw/i386/pc_sysfw.c
+++ b/hw/i386/pc_sysfw.c
@@ -258,16 +258,9 @@ void pc_system_firmware_init(PCMachineState *pcms,
     pc_system_flash_cleanup_unused(pcms);
 }
 
-void x86_firmware_configure(hwaddr gpa, void *ptr, int size)
+static void x86_firmware_configure_sev(hwaddr gpa, void *ptr, int size)
 {
     int ret;
-
-    /*
-     * OVMF places a GUIDed structures in the flash, so
-     * search for them
-     */
-    pc_system_parse_ovmf_flash(ptr, size);
-
     if (sev_enabled()) {
 
         /* Copy the SEV metadata table (if it exists) */
@@ -282,3 +275,20 @@ void x86_firmware_configure(hwaddr gpa, void *ptr, int size)
         sev_encrypt_flash(gpa, ptr, size, &error_fatal);
     }
 }
+
+void x86_firmware_configure(hwaddr gpa, void *ptr, int size)
+{
+    /*
+     * OVMF places a GUIDed structures in the flash, so
+     * search for them
+     */
+    pc_system_parse_ovmf_flash(ptr, size);
+    x86_firmware_configure_sev(gpa, ptr, size);
+}
+
+void x86_firmware_reconfigure(hwaddr gpa, void *ptr, int size)
+{
+    invalidate_ovmf_parsed_metadata();
+    pc_system_parse_ovmf_flash(ptr, size);
+    x86_firmware_configure_sev(gpa, ptr, size);
+}
diff --git a/hw/i386/pc_sysfw_ovmf-stubs.c b/hw/i386/pc_sysfw_ovmf-stubs.c
index aabe78b271..edf890a525 100644
--- a/hw/i386/pc_sysfw_ovmf-stubs.c
+++ b/hw/i386/pc_sysfw_ovmf-stubs.c
@@ -24,3 +24,8 @@ void pc_system_parse_ovmf_flash(uint8_t *flash_ptr, size_t flash_size)
 {
     g_assert_not_reached();
 }
+
+void invalidate_ovmf_parsed_metadata(void)
+{
+    g_assert_not_reached();
+}
diff --git a/hw/i386/pc_sysfw_ovmf.c b/hw/i386/pc_sysfw_ovmf.c
index 07a4c267fa..3244c17a7d 100644
--- a/hw/i386/pc_sysfw_ovmf.c
+++ b/hw/i386/pc_sysfw_ovmf.c
@@ -36,6 +36,11 @@ static bool ovmf_flash_parsed;
 static uint8_t *ovmf_table;
 static int ovmf_table_len;
 
+void invalidate_ovmf_parsed_metadata(void)
+{
+    ovmf_flash_parsed = false;
+}
+
 void pc_system_parse_ovmf_flash(uint8_t *flash_ptr, size_t flash_size)
 {
     uint8_t *ptr;
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 103b54301f..7b0d0c54f5 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -211,6 +211,7 @@ void pc_system_firmware_init(PCMachineState *pcms, MemoryRegion *rom_memory);
 bool pc_system_ovmf_table_find(const char *entry, uint8_t **data,
                                int *data_len);
 void pc_system_parse_ovmf_flash(uint8_t *flash_ptr, size_t flash_size);
+void invalidate_ovmf_parsed_metadata(void);
 
 /* sgx.c */
 void pc_machine_init_sgx_epc(PCMachineState *pcms);
diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h
index d43cb3908e..18c0d6851a 100644
--- a/include/hw/i386/x86.h
+++ b/include/hw/i386/x86.h
@@ -155,5 +155,6 @@ DeviceState *ioapic_init_secondary(GSIState *gsi_state);
 
 /* pc_sysfw.c */
 void x86_firmware_configure(hwaddr gpa, void *ptr, int size);
+void x86_firmware_reconfigure(hwaddr gpa, void *ptr, int size);
 
 #endif
-- 
2.42.0

On Fri, Feb 28, 2025 at 05:12:30PM +0530, Ani Sinha wrote:
> Normally, there is no need to perform firmware reconfiguration once the
> virtual machine has started. Hence, currently ovmf firmware parsing happens only
> once. However, if the firmware changes betweeen boots then reconfiguration needs
> to happen again. Firmware can change if for example the guest brings its own
> firmware bundle and installs it with the help of the hypervisor[1]. Therefore,
> this change introduces a new api with which firmware configuration steps can
> be forced again.
> This is mostly refactoring work. No functional changes. CI pipeline does not
> break with this change.
> 
> 1) https://pretalx.com/kvm-forum-2024/talk/HJSKRQ/
> 
> Signed-off-by: Ani Sinha <anisinha@redhat.com>

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>