diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2023-08-14 13:44:35 +0200 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2023-08-16 21:58:59 +0200 |
| commit | 864bcaa38ee44ec6c0e43f79c2d2997b977e26b2 (patch) | |
| tree | 138e657528645336a8f30df0bbfafc8436313cef /arch | |
| parent | e7c25c441e9e0fa75b4c83e0b26306b702cfe90d (diff) | |
x86/cpu/kvm: Provide UNTRAIN_RET_VM
Similar to how it doesn't make sense to have UNTRAIN_RET have two
untrain calls, it also doesn't make sense for VMEXIT to have an extra
IBPB call.
This cures VMEXIT doing potentially unret+IBPB or double IBPB.
Also, the (SEV) VMEXIT case seems to have been overlooked.
Redefine the meaning of the synthetic IBPB flags to:
- ENTRY_IBPB -- issue IBPB on entry (was: entry + VMEXIT)
- IBPB_ON_VMEXIT -- issue IBPB on VMEXIT
And have 'retbleed=ibpb' set *BOTH* feature flags to ensure it retains
the previous behaviour and issues IBPB on entry+VMEXIT.
The new 'srso=ibpb_vmexit' option only sets IBPB_ON_VMEXIT.
Create UNTRAIN_RET_VM specifically for the VMEXIT case, and have that
check IBPB_ON_VMEXIT.
All this avoids having the VMEXIT case having to check both ENTRY_IBPB
and IBPB_ON_VMEXIT and simplifies the alternatives.
Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121149.109557833@infradead.org
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 11 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 1 | ||||
| -rw-r--r-- | arch/x86/kvm/svm/vmenter.S | 7 |
3 files changed, 14 insertions, 5 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 5285c8e93dff..c55cc243592e 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -299,6 +299,17 @@ #endif .endm +.macro UNTRAIN_RET_VM +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ + defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) + VALIDATE_UNRET_END + ALTERNATIVE_3 "", \ + CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ + "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT, \ + __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH +#endif +.endm + .macro UNTRAIN_RET_FROM_CALL #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ defined(CONFIG_CALL_DEPTH_TRACKING) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6f3e19527286..9026e3fe9f6c 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1054,6 +1054,7 @@ do_cmd_auto: case RETBLEED_MITIGATION_IBPB: setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); + setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT); mitigate_smt = true; break; diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 265452fc9ebe..ef2ebabb059c 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -222,10 +222,7 @@ SYM_FUNC_START(__svm_vcpu_run) * because interrupt handlers won't sanitize 'ret' if the return is * from the kernel. */ - UNTRAIN_RET - - /* SRSO */ - ALTERNATIVE "", "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT + UNTRAIN_RET_VM /* * Clear all general purpose registers except RSP and RAX to prevent @@ -362,7 +359,7 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run) * because interrupt handlers won't sanitize RET if the return is * from the kernel. */ - UNTRAIN_RET + UNTRAIN_RET_VM /* "Pop" @spec_ctrl_intercepted. */ pop %_ASM_BX |