diff options
| author | Borislav Petkov (AMD) <bp@alien8.de> | 2023-11-30 16:26:01 +0300 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2023-12-13 23:07:56 +0300 |
| commit | 30579c8baa5b4bd986420a984dad2940f1ff65d3 (patch) | |
| tree | 2d7f9f091faf187eabb9b9823394e3f8f95561c2 /arch/x86/kernel/head_64.S | |
| parent | a39b6ac3781d46ba18193c9dbb2110f31e9bffe9 (diff) | |
| download | linux-30579c8baa5b4bd986420a984dad2940f1ff65d3.tar.xz | |
x86/sev: Do the C-bit verification only on the BSP
There's no need to do it on every AP.
The C-bit value read on the BSP and also verified there, is used
everywhere from now on.
No functional changes - just a bit faster booting APs.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20231130132601.10317-1-bp@alien8.de
Diffstat (limited to 'arch/x86/kernel/head_64.S')
| -rw-r--r-- | arch/x86/kernel/head_64.S | 31 |
1 files changed, 22 insertions, 9 deletions
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 086a2c3aaaa0..d1dc39af6771 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -114,6 +114,28 @@ SYM_CODE_START_NOALIGN(startup_64) /* Form the CR3 value being sure to include the CR3 modifier */ addq $(early_top_pgt - __START_KERNEL_map), %rax + +#ifdef CONFIG_AMD_MEM_ENCRYPT + mov %rax, %rdi + mov %rax, %r14 + + addq phys_base(%rip), %rdi + + /* + * For SEV guests: Verify that the C-bit is correct. A malicious + * hypervisor could lie about the C-bit position to perform a ROP + * attack on the guest by writing to the unencrypted stack and wait for + * the next RET instruction. + */ + call sev_verify_cbit + + /* + * Restore CR3 value without the phys_base which will be added + * below, before writing %cr3. + */ + mov %r14, %rax +#endif + jmp 1f SYM_CODE_END(startup_64) @@ -193,15 +215,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) addq phys_base(%rip), %rax /* - * For SEV guests: Verify that the C-bit is correct. A malicious - * hypervisor could lie about the C-bit position to perform a ROP - * attack on the guest by writing to the unencrypted stack and wait for - * the next RET instruction. - */ - movq %rax, %rdi - call sev_verify_cbit - - /* * Switch to new page-table * * For the boot CPU this switches to early_top_pgt which still has the |