Most of the SEV support code used to reside in a single C source file
that was included in two places: the core kernel, and the decompressor.
The code that is actually shared with the decompressor was moved into a
separate, shared source file under startup/, on the basis that the
decompressor also executes from the early 1:1 mapping of memory.
However, while the elaborate #VC handling and instruction decoding that
it involves is also performed by the decompressor, it does not actually
occur in the core kernel at early boot, and therefore, does not need to
be part of the confined early startup code.
So split off the #VC handling code and move it back into arch/x86/coco
where it came from, into another C source file that is included from
both the decompressor and the core kernel.
Code movement only - no functional change intended.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250504095230.2932860-31-ardb+git@google.com
sev_snp_enabled() is no longer used outside of the source file that
defines it, so make it static and drop the extern declarations.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250504095230.2932860-29-ardb+git@google.com
Commit:
d54d610243 ("x86/boot/sev: Avoid shared GHCB page for early memory acceptance")
provided a fix for SEV-SNP memory acceptance from the EFI stub when
running at VMPL #0. However, that fix was insufficient for SVSM SEV-SNP
guests running at VMPL >0, as those rely on a SVSM calling area, which
is a shared buffer whose address is programmed into a SEV-SNP MSR, and
the SEV init code that sets up this calling area executes much later
during the boot.
Given that booting via the EFI stub at VMPL >0 implies that the firmware
has configured this calling area already, reuse it for performing memory
acceptance in the EFI stub.
Fixes: fcd042e864 ("x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0")
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250428174322.2780170-2-ardb+git@google.com
Communicating with the hypervisor using the shared GHCB page requires
clearing the C bit in the mapping of that page. When executing in the
context of the EFI boot services, the page tables are owned by the
firmware, and this manipulation is not possible.
So switch to a different API for accepting memory in SEV-SNP guests, one
which is actually supported at the point during boot where the EFI stub
may need to accept memory, but the SEV-SNP init code has not executed
yet.
For simplicity, also switch the memory acceptance carried out by the
decompressor when not booting via EFI - this only involves the
allocation for the decompressed kernel, and is generally only called
after kexec, as normal boot will jump straight into the kernel from the
EFI stub.
Fixes: 6c32117963 ("x86/sev: Add SNP-specific unaccepted memory support")
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250404082921.2767593-8-ardb+git@google.com # discussion thread #1
Link: https://lore.kernel.org/r/20250410132850.3708703-2-ardb+git@google.com # discussion thread #2
Link: https://lore.kernel.org/r/20250417202120.1002102-2-ardb+git@google.com # final submission
Add SNP-specific hooks to the unaccepted memory support in the boot
path (__accept_memory()) and the core kernel (accept_memory()) in order
to support booting SNP guests when unaccepted memory is present. Without
this support, SNP guests will fail to boot and/or panic() when unaccepted
memory is present in the EFI memory map.
The process of accepting memory under SNP involves invoking the hypervisor
to perform a page state change for the page to private memory and then
issuing a PVALIDATE instruction to accept the page.
Since the boot path and the core kernel paths perform similar operations,
move the pvalidate_pages() and vmgexit_psc() functions into sev-shared.c
to avoid code duplication.
Create the new header file arch/x86/boot/compressed/sev.h because adding
the function declaration to any of the existing SEV related header files
pulls in too many other header files, causing the build to fail.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a52fa69f460fd1876d70074b20ad68210dfc31dd.1686063086.git.thomas.lendacky@amd.com
