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[PATCH v3 48/49] hw/i386/sev: Use guest_memfd for legacy ROMs
From: |
Michael Roth |
Subject: |
[PATCH v3 48/49] hw/i386/sev: Use guest_memfd for legacy ROMs |
Date: |
Wed, 20 Mar 2024 03:39:44 -0500 |
TODO: make this SNP-specific if TDX disables legacy ROMs in general
Current SNP guest kernels will attempt to access these regions with
with C-bit set, so guest_memfd is needed to handle that. Otherwise,
kvm_convert_memory() will fail when the guest kernel tries to access it
and QEMU attempts to call KVM_SET_MEMORY_ATTRIBUTES to set these ranges
to private.
Whether guests should actually try to access ROM regions in this way (or
need to deal with legacy ROM regions at all), is a separate issue to be
addressed on kernel side, but current SNP guest kernels will exhibit
this behavior and so this handling is needed to allow QEMU to continue
running existing SNP guest kernels.
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
hw/i386/pc.c | 13 +++++++++----
hw/i386/pc_sysfw.c | 13 ++++++++++---
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index feb7a93083..5feaeb43ee 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1011,10 +1011,15 @@ void pc_memory_init(PCMachineState *pcms,
pc_system_firmware_init(pcms, rom_memory);
option_rom_mr = g_malloc(sizeof(*option_rom_mr));
- 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 (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,
diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
index 9dbb3f7337..850f86edd4 100644
--- a/hw/i386/pc_sysfw.c
+++ b/hw/i386/pc_sysfw.c
@@ -54,8 +54,13 @@ static void pc_isa_bios_init(MemoryRegion *rom_memory,
/* map the last 128KB of the BIOS in ISA space */
isa_bios_size = MIN(flash_size, 128 * KiB);
isa_bios = g_malloc(sizeof(*isa_bios));
- memory_region_init_ram(isa_bios, NULL, "isa-bios", isa_bios_size,
- &error_fatal);
+ if (machine_require_guest_memfd(current_machine)) {
+ memory_region_init_ram_guest_memfd(isa_bios, NULL, "isa-bios",
+ isa_bios_size, &error_fatal);
+ } else {
+ memory_region_init_ram(isa_bios, NULL, "isa-bios", isa_bios_size,
+ &error_fatal);
+ }
memory_region_add_subregion_overlap(rom_memory,
0x100000 - isa_bios_size,
isa_bios,
@@ -68,7 +73,9 @@ static void pc_isa_bios_init(MemoryRegion *rom_memory,
((uint8_t*)flash_ptr) + (flash_size - isa_bios_size),
isa_bios_size);
- memory_region_set_readonly(isa_bios, true);
+ if (!machine_require_guest_memfd(current_machine)) {
+ memory_region_set_readonly(isa_bios, true);
+ }
}
static PFlashCFI01 *pc_pflash_create(PCMachineState *pcms,
--
2.25.1
- [PATCH v3 42/49] i386/sev: Add support for SNP CPUID validation, (continued)
- [PATCH v3 42/49] i386/sev: Add support for SNP CPUID validation, Michael Roth, 2024/03/20
- [PATCH v3 43/49] qapi, i386: Move kernel-hashes to SevCommonProperties, Michael Roth, 2024/03/20
- [PATCH v3 44/49] i386/sev: Extract build_kernel_loader_hashes, Michael Roth, 2024/03/20
- [PATCH v3 45/49] i386/sev: Reorder struct declarations, Michael Roth, 2024/03/20
- [PATCH v3 46/49] i386/sev: Allow measured direct kernel boot on SNP, Michael Roth, 2024/03/20
- [PATCH v3 47/49] hw/i386/sev: Add support to encrypt BIOS when SEV-SNP is enabled, Michael Roth, 2024/03/20
- [PATCH v3 48/49] hw/i386/sev: Use guest_memfd for legacy ROMs,
Michael Roth <=
- [PATCH v3 49/49] hw/i386: Add support for loading BIOS using guest_memfd, Michael Roth, 2024/03/20
- [PATCH v3 04/49] [HACK] linux-headers: Update headers for 6.8 + kvm-coco-queue + SNP, Michael Roth, 2024/03/20
- [PATCH v3 05/49] [TEMP] hw/i386: Remove redeclaration of struct setup_data, Michael Roth, 2024/03/20
- [PATCH v3 06/49] RAMBlock: Add support of KVM private guest memfd, Michael Roth, 2024/03/20
- [PATCH v3 07/49] HostMem: Add mechanism to opt in kvm guest memfd via MachineState, Michael Roth, 2024/03/20
- [PATCH v3 08/49] trace/kvm: Split address space and slot id in trace_kvm_set_user_memory(), Michael Roth, 2024/03/20
- Re: [PATCH RFC v3 00/49] Add AMD Secure Nested Paging (SEV-SNP) support, Paolo Bonzini, 2024/03/20