diff options
| author | Sean Christopherson <seanjc@google.com> | 2025-11-13 15:37:40 -0800 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-11-18 16:22:41 -0800 |
| commit | afb99ffbd5825bfbc88e8052bc5514e6ebdfec5e (patch) | |
| tree | 36f3e5c296fb8a702c833b0ffaa7ce02f978aaee /arch/x86/include | |
| parent | aba7de6088be5a3b5d766c5f7fdb5d0790ff8f13 (diff) | |
x86/bugs: Decouple ALTERNATIVE usage from VERW macro definition
Decouple the use of ALTERNATIVE from the encoding of VERW to clear CPU
buffers so that KVM can use ALTERNATIVE_2 to handle "always clear buffers"
and "clear if guest can access host MMIO" in a single statement.
No functional change intended.
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Link: https://patch.msgid.link/20251113233746.1703361-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 27 |
1 files changed, 16 insertions, 11 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 08ed5a2e46a5..cb36a8ea00d3 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -308,24 +308,29 @@ * CFLAGS.ZF. * Note: Only the memory operand variant of VERW clears the CPU buffers. */ -.macro __CLEAR_CPU_BUFFERS feature #ifdef CONFIG_X86_64 - ALTERNATIVE "", "verw x86_verw_sel(%rip)", \feature +#define VERW verw x86_verw_sel(%rip) #else - /* - * In 32bit mode, the memory operand must be a %cs reference. The data - * segments may not be usable (vm86 mode), and the stack segment may not - * be flat (ESPFIX32). - */ - ALTERNATIVE "", "verw %cs:x86_verw_sel", \feature +/* + * In 32bit mode, the memory operand must be a %cs reference. The data segments + * may not be usable (vm86 mode), and the stack segment may not be flat (ESPFIX32). + */ +#define VERW verw %cs:x86_verw_sel #endif -.endm +/* + * Provide a stringified VERW macro for simple usage, and a non-stringified + * VERW macro for use in more elaborate sequences, e.g. to encode a conditional + * VERW within an ALTERNATIVE. + */ +#define __CLEAR_CPU_BUFFERS __stringify(VERW) + +/* If necessary, emit VERW on exit-to-userspace to clear CPU buffers. */ #define CLEAR_CPU_BUFFERS \ - __CLEAR_CPU_BUFFERS X86_FEATURE_CLEAR_CPU_BUF + ALTERNATIVE "", __CLEAR_CPU_BUFFERS, X86_FEATURE_CLEAR_CPU_BUF #define VM_CLEAR_CPU_BUFFERS \ - __CLEAR_CPU_BUFFERS X86_FEATURE_CLEAR_CPU_BUF_VM + ALTERNATIVE "", __CLEAR_CPU_BUFFERS, X86_FEATURE_CLEAR_CPU_BUF_VM #ifdef CONFIG_X86_64 .macro CLEAR_BRANCH_HISTORY |