linux-kernel - Re: [PATCH v3 00/17] x86: head

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Date:   Tue, 22 Nov 2022 14:48:09 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Michael Roth <michael.roth@....com>
Subject: Re: [PATCH v3 00/17] x86: head_64.S spring cleaning

On 11/22/22 10:10, Ard Biesheuvel wrote:
> After doing some cleanup work on the EFI code in head_64.S, the mixed
> mode code in particular, I noticed that the memory encryption pieces
> could use some attention as well, so I cleaned that up too.
> 
> Changes since v2:
> - add some clarifying comments to the EFI mixed mode changes
> - include patch to make the EFI handover protocol optional that was sent
>    out separately before
> - rebase onto tip/master
> 
> Changes since v1:
> - at Boris's request, split the patches into smaller ones that are
>    easier to review
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Michael Roth <michael.roth@....com>

This causes an SEV guest to blow up on boot in the early boot code. It
looks like the stack pointer is not valid and it triple faults on a pushq
instruction (pushq $__KERNEL_CS in arch/x86/boot/compressed/head_64.S of
startup_64).

Here is the Qemu register dump:
RAX=00000000029cc260 RBX=ffffffffdd98c000 RCX=0000000000000010 RDX=0000000000000002
RSI=000000003dec1000 RDI=0000000000000000 RBP=ffffffffdb000000 RSP=ffffffffde36e000
R8 =000000003dec1410 R9 =000000003dec13fc R10=000000000000006c R11=0000000000000000
R12=0000000000000000 R13=0000000000000001 R14=0000000000000004 R15=000000003eacdf44
RIP=0000000002000263 RFL=00200002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 00000000 00000000
CS =0038 0000000000000000 ffffffff 00a09b00 DPL=0 CS64 [-RA]
SS =0000 0000000000000000 00000000 00000000
DS =0000 0000000000000000 00000000 00000000
FS =0000 0000000000000000 00000000 00000000
GS =0000 0000000000000000 00000000 00000000
LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
TR =0000 0000000000000000 0000ffff 00008b00 DPL=0 TSS64-busy
GDT=     00000000029cc270 0000002f
IDT=     000000003f55e018 00000fff
CR0=80010033 CR2=ffffffffde36dff8 CR3=000000003fc01000 CR4=00000668
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000d00

Thanks,
Tom

> 
> Ard Biesheuvel (17):
>    x86/compressed: efi-mixed: rename efi_thunk_64.S to efi-mixed.S
>    x86/compressed: efi-mixed: move 32-bit entrypoint code into .text
>      section
>    x86/compressed: efi-mixed: move bootargs parsing out of 32-bit startup
>      code
>    x86/compressed: efi-mixed: move efi32_pe_entry into .text section
>    x86/compressed: efi-mixed: move efi32_entry out of head_64.S
>    x86/compressed: efi-mixed: move efi32_pe_entry() out of head_64.S
>    x86/compressed: efi: merge multiple definitions of image_offset into
>      one
>    x86/compressed: efi-mixed: simplify IDT/GDT preserve/restore
>    x86/compressed: avoid touching ECX in startup32_set_idt_entry()
>    x86/compressed: pull global variable ref up into startup32_load_idt()
>    x86/compressed: move startup32_load_idt() into .text section
>    x86/compressed: move startup32_load_idt() out of head_64.S
>    x86/compressed: move startup32_check_sev_cbit() into .text
>    x86/compressed: move startup32_check_sev_cbit() out of head_64.S
>    x86/compressed: adhere to calling convention in
>      get_sev_encryption_bit()
>    x86/compressed: only build mem_encrypt.S if AMD_MEM_ENCRYPT=y
>    efi: x86: Make the deprecated EFI handover protocol optional
> 
>   arch/x86/Kconfig                        |  17 +
>   arch/x86/boot/compressed/Makefile       |   8 +-
>   arch/x86/boot/compressed/efi_mixed.S    | 351 ++++++++++++++++++++
>   arch/x86/boot/compressed/efi_thunk_64.S | 195 -----------
>   arch/x86/boot/compressed/head_32.S      |   4 -
>   arch/x86/boot/compressed/head_64.S      | 303 +----------------
>   arch/x86/boot/compressed/mem_encrypt.S  | 152 ++++++++-
>   arch/x86/boot/header.S                  |   2 +-
>   arch/x86/boot/tools/build.c             |   2 +
>   drivers/firmware/efi/libstub/x86-stub.c |   2 +-
>   10 files changed, 533 insertions(+), 503 deletions(-)
>   create mode 100644 arch/x86/boot/compressed/efi_mixed.S
>   delete mode 100644 arch/x86/boot/compressed/efi_thunk_64.S
>