| Message ID | 20250504095230.2932860-25-ardb+git@google.com |
|---|---|
| Headers | show |
| Series | x86: strict separation of startup code | expand |
On Sun, May 04, 2025 at 11:52:30AM +0200, Ard Biesheuvel wrote: > arch/x86/boot/compressed/Makefile | 6 +- > arch/x86/boot/compressed/misc.h | 12 +- > arch/x86/boot/compressed/pgtable_64.c | 12 - > arch/x86/boot/compressed/sev-handle-vc.c | 134 +++ > arch/x86/boot/compressed/sev.c | 210 +--- > arch/x86/boot/compressed/sev.h | 21 +- > arch/x86/boot/compressed/vmlinux.lds.S | 1 + > arch/x86/boot/startup/Makefile | 21 + > arch/x86/boot/startup/exports.h | 14 + > arch/x86/boot/startup/gdt_idt.c | 17 +- > arch/x86/boot/startup/map_kernel.c | 18 +- > arch/x86/boot/startup/sev-shared.c | 804 +------------- > arch/x86/boot/startup/sev-startup.c | 1169 +------------------- > arch/x86/boot/startup/sme.c | 45 +- > arch/x86/coco/core.c | 2 + > arch/x86/coco/sev/Makefile | 6 +- > arch/x86/coco/sev/core.c | 189 +++- > arch/x86/coco/sev/{sev-nmi.c => sev-noinstr.c} | 74 ++ Can we drop the "sev-" prefix to filenames which are already in sev/ filepaths? > arch/x86/coco/sev/vc-handle.c | 1060 ++++++++++++++++++ > arch/x86/coco/sev/vc-shared.c | 614 ++++++++++ > arch/x86/include/asm/init.h | 6 - > arch/x86/include/asm/linkage.h | 10 + > arch/x86/include/asm/pgtable_64_types.h | 43 +- > arch/x86/include/asm/setup.h | 2 + > arch/x86/include/asm/sev-internal.h | 30 +- > arch/x86/include/asm/sev.h | 78 ++ Pfff, sev-internal and sev. I guess I'll know how the new structure would look like once I go through this but there are so many sev* files now. Can we tone that down pls, through aggregation, moving up into headers and so on? Thx.
On Wed, 7 May 2025 at 11:53, Borislav Petkov <bp@alien8.de> wrote: > > On Sun, May 04, 2025 at 11:52:30AM +0200, Ard Biesheuvel wrote: > > arch/x86/boot/compressed/Makefile | 6 +- > > arch/x86/boot/compressed/misc.h | 12 +- > > arch/x86/boot/compressed/pgtable_64.c | 12 - > > arch/x86/boot/compressed/sev-handle-vc.c | 134 +++ > > arch/x86/boot/compressed/sev.c | 210 +--- > > arch/x86/boot/compressed/sev.h | 21 +- > > arch/x86/boot/compressed/vmlinux.lds.S | 1 + > > arch/x86/boot/startup/Makefile | 21 + > > arch/x86/boot/startup/exports.h | 14 + > > arch/x86/boot/startup/gdt_idt.c | 17 +- > > arch/x86/boot/startup/map_kernel.c | 18 +- > > arch/x86/boot/startup/sev-shared.c | 804 +------------- > > arch/x86/boot/startup/sev-startup.c | 1169 +------------------- > > arch/x86/boot/startup/sme.c | 45 +- > > arch/x86/coco/core.c | 2 + > > arch/x86/coco/sev/Makefile | 6 +- > > arch/x86/coco/sev/core.c | 189 +++- > > arch/x86/coco/sev/{sev-nmi.c => sev-noinstr.c} | 74 ++ > > Can we drop the "sev-" prefix to filenames which are already in sev/ > filepaths? > Sure. > > arch/x86/coco/sev/vc-handle.c | 1060 ++++++++++++++++++ > > arch/x86/coco/sev/vc-shared.c | 614 ++++++++++ > > arch/x86/include/asm/init.h | 6 - > > arch/x86/include/asm/linkage.h | 10 + > > arch/x86/include/asm/pgtable_64_types.h | 43 +- > > arch/x86/include/asm/setup.h | 2 + > > arch/x86/include/asm/sev-internal.h | 30 +- > > arch/x86/include/asm/sev.h | 78 ++ > > Pfff, sev-internal and sev. > > I guess I'll know how the new structure would look like once I go through this > but there are so many sev* files now. > > Can we tone that down pls, through aggregation, moving up into headers and so > on? > I think the main issue with this code is that everything was in a single source file, with no structure or layering whatsoever. So I'd actually argue for splitting this up even more rather than bundling it all together, although the sev vs sev-internal distinction is a bit dubious - it would be better to split this across functional lines. I added sev-internal.h so that that single mother-of-all-source-files could be hacked up without exposing implementation details to external users that were hidden before. I.e., the high-level APIs that other callers need to use should be in sev.h, and the implementation of that API should be carved up meaningfully. For example, perhaps the #VC handling stuff (which now lives in a separate source file) could be exposed via sev-vc.h, and only included in places where that particular functionality is being used.
On Wed, May 07, 2025 at 02:05:37PM +0200, Ard Biesheuvel wrote: > So I'd actually argue for splitting this up even more rather than > bundling it all together, Splitting it into logically separated bits? Yes. Just because: no. The SEV stuff is still largely in motion so once it starts settling down, splitting it would be the first thing that irks me and I'll go do it. > although the sev vs sev-internal distinction is a bit dubious - it would be > better to split this across functional lines. > > I added sev-internal.h so that that single mother-of-all-source-files > could be hacked up without exposing implementation details to external > users that were hidden before. I.e., the high-level APIs that other > callers need to use should be in sev.h, and the implementation of that > API should be carved up meaningfully. For example, perhaps the #VC > handling stuff (which now lives in a separate source file) could be > exposed via sev-vc.h, and only included in places where that > particular functionality is being used. Right, please put those considerations in the commit messages - it helps a lot with the review. Thx.
From: Ard Biesheuvel <ardb@kernel.org> This RFT series implements a strict separation between startup code and ordinary code, where startup code is built in a way that tolerates being invoked from the initial 1:1 mapping of memory. The existsing approach of emitting this code into .head.text and checking for absolute relocations in that section is not 100% safe, and produces diagnostics that are sometimes difficult to interpret. Instead, rely on symbol prefixes, similar to how this is implemented for the EFI stub and for the startup code in the arm64 port. This ensures that startup code can only call other startup code, unless a special symbol alias is emitted that exposes a non-startup routine to the startup code. This is somewhat intrusive, as there are many data objects that are referenced both by startup code and by ordinary code, and an alias needs to be emitted for each of those. If startup code references anything that has not been made available to it explicitly, a build time link error will occur. This ultimately allows the .head.text section to be dropped entirely, as it no longer has a special significance. Instead, code that only executes at boot is emitted into .init.text as it should. Change since RFC/v1: - Include a major disentanglement/refactor of the SEV-SNP startup code, so that only code that really needs to run from the 1:1 mapping is included in the startup/ code - Incorporate some early notes from Ingo Build tested defconfig and allmodconfig !!! Boot tested on non-SEV guest ONLY !!!! Again, I will need to lean on Tom to determine whether this breaks SEV-SNP guest boot. As I mentioned before, I am still waiting for SEV-SNP capable hardware to be delivered. Cc: Borislav Petkov <bp@alien8.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Dionna Amalie Glaze <dionnaglaze@google.com> Cc: Kevin Loughlin <kevinloughlin@google.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Ard Biesheuvel (23): x86/boot: Move early_setup_gdt() back into head64.c x86/boot: Disregard __supported_pte_mask in __startup_64() x86/boot: Drop global variables keeping track of LA57 state x86/sev: Make sev_snp_enabled() a static function x86/sev: Move instruction decoder into separate source file x86/sev: Disentangle #VC handling code from startup code x86/sev: Separate MSR and GHCB based snp_cpuid() via a callback x86/sev: Fall back to early page state change code only during boot x86/sev: Move GHCB page based HV communication out of startup code x86/sev: Use boot SVSM CA for all startup and init code x86/boot: Drop redundant RMPADJUST in SEV SVSM presence check x86/sev: Unify SEV-SNP hypervisor feature check x86/linkage: Add SYM_PIC_ALIAS() macro helper to emit symbol aliases x86/boot: Add a bunch of PIC aliases x86/boot: Provide __pti_set_user_pgtbl() to startup code x86/sev: Provide PIC aliases for SEV related data objects x86/sev: Move __sev_[get|put]_ghcb() into separate noinstr object x86/sev: Export startup routines for ordinary use x86/boot: Created a confined code area for startup code x86/boot: Move startup code out of __head section x86/boot: Disallow absolute symbol references in startup code x86/boot: Revert "Reject absolute references in .head.text" x86/boot: Get rid of the .head.text section arch/x86/boot/compressed/Makefile | 6 +- arch/x86/boot/compressed/misc.h | 12 +- arch/x86/boot/compressed/pgtable_64.c | 12 - arch/x86/boot/compressed/sev-handle-vc.c | 134 +++ arch/x86/boot/compressed/sev.c | 210 +--- arch/x86/boot/compressed/sev.h | 21 +- arch/x86/boot/compressed/vmlinux.lds.S | 1 + arch/x86/boot/startup/Makefile | 21 + arch/x86/boot/startup/exports.h | 14 + arch/x86/boot/startup/gdt_idt.c | 17 +- arch/x86/boot/startup/map_kernel.c | 18 +- arch/x86/boot/startup/sev-shared.c | 804 +------------- arch/x86/boot/startup/sev-startup.c | 1169 +------------------- arch/x86/boot/startup/sme.c | 45 +- arch/x86/coco/core.c | 2 + arch/x86/coco/sev/Makefile | 6 +- arch/x86/coco/sev/core.c | 189 +++- arch/x86/coco/sev/{sev-nmi.c => sev-noinstr.c} | 74 ++ arch/x86/coco/sev/vc-handle.c | 1060 ++++++++++++++++++ arch/x86/coco/sev/vc-shared.c | 614 ++++++++++ arch/x86/include/asm/init.h | 6 - arch/x86/include/asm/linkage.h | 10 + arch/x86/include/asm/pgtable_64_types.h | 43 +- arch/x86/include/asm/setup.h | 2 + arch/x86/include/asm/sev-internal.h | 30 +- arch/x86/include/asm/sev.h | 78 ++ arch/x86/kernel/cpu/common.c | 3 +- arch/x86/kernel/head64.c | 27 +- arch/x86/kernel/head_32.S | 2 +- arch/x86/kernel/head_64.S | 18 +- arch/x86/kernel/setup.c | 1 + arch/x86/kernel/vmlinux.lds.S | 11 +- arch/x86/lib/memcpy_64.S | 1 + arch/x86/lib/memset_64.S | 1 + arch/x86/lib/retpoline.S | 2 + arch/x86/mm/kasan_init_64.c | 3 - arch/x86/mm/mem_encrypt_amd.c | 2 + arch/x86/mm/mem_encrypt_boot.S | 6 +- arch/x86/mm/pgtable.c | 1 + arch/x86/platform/pvh/head.S | 2 +- arch/x86/tools/relocs.c | 8 +- tools/objtool/arch/x86/decode.c | 6 +- 42 files changed, 2367 insertions(+), 2325 deletions(-) create mode 100644 arch/x86/boot/compressed/sev-handle-vc.c create mode 100644 arch/x86/boot/startup/exports.h rename arch/x86/coco/sev/{sev-nmi.c => sev-noinstr.c} (61%) create mode 100644 arch/x86/coco/sev/vc-handle.c create mode 100644 arch/x86/coco/sev/vc-shared.c base-commit: 18ea89eae404d119ced26d80ac3e62255ce15409