On Tue, 31 Jan 2023 at 01:49, Dionna Glaze <dionnaglaze@xxxxxxxxxx> wrote: > > This patch depends on Kirill A. Shutemov's series > > [PATCHv8 00/14] mm, x86/cc: Implement support for unaccepted memory > > The UEFI v2.9 specification includes a new memory type to be used in > environments where the OS must accept memory that is provided from its > host. Before the introduction of this memory type, all memory was > accepted eagerly in the firmware. In order for the firmware to safely > stop accepting memory on the OS's behalf, the OS must affirmatively > indicate support to the firmware. This is only a problem for AMD > SEV-SNP, since Linux has had support for it since 5.19. The other > technology that can make use of unaccepted memory, Intel TDX, does not > yet have Linux support, so it can strictly require unaccepted memory > support as a dependency of CONFIG_TDX and not require communication with > the firmware. > > Enabling unaccepted memory requires calling a 0-argument enablement > protocol before ExitBootServices. This call is only made if the kernel > is compiled with UNACCEPTED_MEMORY=y > > This protocol will be removed after the end of life of the first LTS > that includes it, in order to give firmware implementations an > expiration date for it. When the protocol is removed, firmware will > strictly infer that a SEV-SNP VM is running an OS that supports the > unaccepted memory type. At the earliest convenience, when unaccepted > memory support is added to Linux, SEV-SNP may take strict dependence in > it. After the firmware removes support for the protocol, this patch > should be reverted. > > Change since v1: > * protocol name, as it is in OVMF > https://github.com/tianocore/edk2/commit/26847fb6be7fff83a834a3154224588afede0073 > * protocol typedef moved before struct definition. > > Cc: Ard Biescheuvel <ardb@xxxxxxxxxx> > Cc: "Min M. Xu" <min.m.xu@xxxxxxxxx> > Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx> > Cc: James Bottomley <jejb@xxxxxxxxxxxxx> > Cc: Tom Lendacky <Thomas.Lendacky@xxxxxxx> > Cc: Jiewen Yao <jiewen.yao@xxxxxxxxx> > Cc: Erdem Aktas <erdemaktas@xxxxxxxxxx> > Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxxxx> > > Signed-off-by: Dionna Glaze <dionnaglaze@xxxxxxxxxx> > --- > drivers/firmware/efi/libstub/x86-stub.c | 37 +++++++++++++++++++++++++ > include/linux/efi.h | 4 +++ > 2 files changed, 41 insertions(+) > > diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c > index a0bfd31358ba..e4c04444edab 100644 > --- a/drivers/firmware/efi/libstub/x86-stub.c > +++ b/drivers/firmware/efi/libstub/x86-stub.c > @@ -26,6 +26,17 @@ const efi_dxe_services_table_t *efi_dxe_table; > u32 image_offset __section(".data"); > static efi_loaded_image_t *image = NULL; > > +typedef union sev_memory_acceptance_protocol sev_memory_acceptance_protocol_t; > +union sev_memory_acceptance_protocol { > + struct { > + efi_status_t (__efiapi *allow_unaccepted_memory)( > + sev_memory_acceptance_protocol_t *); > + }; > + struct { > + u32 allow_unaccepted_memory; > + } mixed_mode; > +}; > + > static efi_status_t > preserve_pci_rom_image(efi_pci_io_protocol_t *pci, struct pci_setup_rom **__rom) > { > @@ -310,6 +321,30 @@ setup_memory_protection(unsigned long image_base, unsigned long image_size) > #endif > } > > + > +static void setup_unaccepted_memory(void) > +{ > + efi_guid_t mem_acceptance_proto = OVMF_SEV_MEMORY_ACCEPTANCE_PROTOCOL_GUID; > + sev_memory_acceptance_protocol_t *proto; > + efi_status_t status; > + > + if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) Do we need to check for IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT) here as well? > + return; > + > + /* > + * Enable unaccepted memory before calling exit boot services in order > + * for the UEFI to not accept all memory on EBS. > + */ > + status = efi_bs_call(locate_protocol, &mem_acceptance_proto, NULL, > + (void **)&proto); > + if (status != EFI_SUCCESS) > + return; > + > + status = efi_call_proto(proto, allow_unaccepted_memory); > + if (status != EFI_SUCCESS) > + efi_err("Memory acceptance protocol failed\n"); > +} > + > static const efi_char16_t apple[] = L"Apple"; > > static void setup_quirks(struct boot_params *boot_params, > @@ -899,6 +934,8 @@ asmlinkage unsigned long efi_main(efi_handle_t handle, > > setup_quirks(boot_params, bzimage_addr, buffer_end - buffer_start); > > + setup_unaccepted_memory(); > + > status = exit_boot(boot_params, handle); > if (status != EFI_SUCCESS) { > efi_err("exit_boot() failed!\n"); > diff --git a/include/linux/efi.h b/include/linux/efi.h > index 4b27519143f5..ac812978a03a 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -434,6 +434,10 @@ void efi_native_runtime_setup(void); > #define DELLEMC_EFI_RCI2_TABLE_GUID EFI_GUID(0x2d9f28a2, 0xa886, 0x456a, 0x97, 0xa8, 0xf1, 0x1e, 0xf2, 0x4f, 0xf4, 0x55) > #define AMD_SEV_MEM_ENCRYPT_GUID EFI_GUID(0x0cf29b71, 0x9e51, 0x433a, 0xa3, 0xb7, 0x81, 0xf3, 0xab, 0x16, 0xb8, 0x75) > > +/* OVMF protocol GUIDs */ > +#define OVMF_SEV_MEMORY_ACCEPTANCE_PROTOCOL_GUID EFI_GUID(0xc5a010fe, 0x38a7, 0x4531, 0x8a, 0x4a, 0x05, 0x00, 0xd2, 0xfd, 0x16, 0x49) > + > + > typedef struct { > efi_guid_t guid; > u64 table; > -- > 2.39.1.456.gfc5497dd1b-goog >
