[PATCH v6 20/60] i386/tdx: Don't initialize pc.rom for TDX VMs

Xiaoyao Li
2024-11-05T06:37:48Z

For TDX, the address below 1MB are entirely general RAM. No need to
initialize pc.rom memory region for TDs.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
This is more as a workaround of the issue that for q35 machine type, the
real memslot update (which requires memslot deletion )for pc.rom happens
after tdx_init_memory_region. It leads to the private memory ADD'ed
before get lost. I haven't work out a good solution to resolve the
order issue. So just skip the pc.rom setup to avoid memslot deletion.
---
hw/i386/pc.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 2047633e4cf7..4a23856aed47 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -43,6 +43,7 @@
#include "sysemu/xen.h"
#include "sysemu/reset.h"
#include "kvm/kvm_i386.h"
+#include "kvm/tdx.h"
#include "hw/xen/xen.h"
#include "qapi/qmp/qlist.h"
#include "qemu/error-report.h"
@@ -966,21 +967,23 @@ void pc_memory_init(PCMachineState *pcms,
/* Initialize PC system firmware */
pc_system_firmware_init(pcms, rom_memory);

- option_rom_mr = g_malloc(sizeof(*option_rom_mr));
- if (machine_require_guest_memfd(machine)) {
- memory_region_init_ram_guest_memfd(option_rom_mr, NULL, "pc.rom",
- PC_ROM_SIZE, &error_fatal);
- } else {
- memory_region_init_ram(option_rom_mr, NULL, "pc.rom", PC_ROM_SIZE,
- &error_fatal);
- if (pcmc->pci_enabled) {
- memory_region_set_readonly(option_rom_mr, true);
+ if (!is_tdx_vm()) {
+ option_rom_mr = g_malloc(sizeof(*option_rom_mr));
+ if (machine_require_guest_memfd(machine)) {
+ memory_region_init_ram_guest_memfd(option_rom_mr, NULL, "pc.rom",
+ PC_ROM_SIZE, &error_fatal);
+ } else {
+ memory_region_init_ram(option_rom_mr, NULL, "pc.rom", PC_ROM_SIZE,
+ &error_fatal);
+ if (pcmc->pci_enabled) {
+ memory_region_set_readonly(option_rom_mr, true);
+ }
}
+ memory_region_add_subregion_overlap(rom_memory,
+ PC_ROM_MIN_VGA,
+ option_rom_mr,
+ 1);
}
- memory_region_add_subregion_overlap(rom_memory,
- PC_ROM_MIN_VGA,
- option_rom_mr,
- 1);

fw_cfg = fw_cfg_arch_create(machine,
x86ms->boot_cpus, x86ms->apic_id_limit);
--
2.34.1