Mailing List Archive

commit ccc6603b79749e45cbe638939fbb609342f440dd
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Fri Mar 22 14:33:17 2024 +0000
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Tue Apr 9 16:45:01 2024 +0100

x86/spec-ctrl: Simplify DO_COND_IBPB

With the prior refactoring, SPEC_CTRL_ENTRY_{PV,INTR} both load SCF into %ebx,
and handle the conditional safety including skipping if interrupting Xen.

Therefore, we can drop the maybexen parameter and the conditional safety.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
(cherry picked from commit 2378d16a931de0e62c03669169989e9437306abe)
---
xen/arch/x86/include/asm/spec_ctrl_asm.h | 30 ++++++++----------------------
1 file changed, 8 insertions(+), 22 deletions(-)

diff --git a/xen/arch/x86/include/asm/spec_ctrl_asm.h b/xen/arch/x86/include/asm/spec_ctrl_asm.h
index 667ec7ffe0..c80717e421 100644
--- a/xen/arch/x86/include/asm/spec_ctrl_asm.h
+++ b/xen/arch/x86/include/asm/spec_ctrl_asm.h
@@ -75,33 +75,21 @@
* - SPEC_CTRL_EXIT_TO_{SVM,VMX}
*/

-.macro DO_SPEC_CTRL_COND_IBPB maybexen:req
+.macro DO_COND_IBPB
/*
- * Requires %rsp=regs (also cpuinfo if !maybexen)
- * Requires %r14=stack_end (if maybexen), %rdx=0
- * Clobbers %rax, %rcx, %rdx
+ * Requires %rbx=SCF, %rdx=0
+ * Clobbers %rax, %rcx
*
- * Conditionally issue IBPB if SCF_entry_ibpb is active. In the maybexen
- * case, we can safely look at UREGS_cs to skip taking the hit when
- * interrupting Xen.
+ * Conditionally issue IBPB if SCF_entry_ibpb is active.
*/
- .if \maybexen
- testb $SCF_entry_ibpb, STACK_CPUINFO_FIELD(scf)(%r14)
- jz .L\@_skip
- testb $3, UREGS_cs(%rsp)
- .else
- testb $SCF_entry_ibpb, CPUINFO_scf(%rsp)
- .endif
+ testb $SCF_entry_ibpb, %bl
jz .L\@_skip

mov $MSR_PRED_CMD, %ecx
mov $PRED_CMD_IBPB, %eax
wrmsr
- jmp .L\@_done

.L\@_skip:
- lfence
-.L\@_done:
.endm

.macro DO_OVERWRITE_RSB tmp=rax xu
@@ -256,8 +244,7 @@
*/
movzbl STACK_CPUINFO_FIELD(scf)(%r14), %ebx

- ALTERNATIVE "", __stringify(DO_SPEC_CTRL_COND_IBPB maybexen=0), \
- X86_FEATURE_IBPB_ENTRY_PV
+ ALTERNATIVE "", DO_COND_IBPB, X86_FEATURE_IBPB_ENTRY_PV

ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV

@@ -286,8 +273,7 @@
testb $3, UREGS_cs(%rsp)
jz .L\@_skip

- ALTERNATIVE "", __stringify(DO_SPEC_CTRL_COND_IBPB maybexen=1), \
- X86_FEATURE_IBPB_ENTRY_PV
+ ALTERNATIVE "", DO_COND_IBPB, X86_FEATURE_IBPB_ENTRY_PV

ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV

@@ -327,7 +313,7 @@
* Clobbers %rax, %rbx, %rcx, %rdx
*
* This is logical merge of:
- * DO_SPEC_CTRL_COND_IBPB maybexen=0
+ * DO_COND_IBPB
* DO_OVERWRITE_RSB
* DO_SPEC_CTRL_ENTRY maybexen=1
* but with conditionals rather than alternatives.
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.18