[Xen-devel] [PATCH 1/2] xen/x86: Don't hold TRAPBOUNCE_flags in %cl during create_bounce_frame

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

TRAPBOUNCE_flags are always available via a displacement from %rdx.  This
allows all of %rcx to be used as a scratch register.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/x86_64/compat/entry.S | 5 ++---
 xen/arch/x86/x86_64/entry.S        | 5 ++---
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index 927439d..36a8eae 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -263,11 +263,10 @@ compat_create_bounce_frame:
         movl  UREGS_rsp+8(%rsp),%esi
 .Lft4:  mov   UREGS_ss+8(%rsp),%fs
 2:
-        movb  TRAPBOUNCE_flags(%rdx),%cl
         subl  $3*4,%esi
         movq  VCPU_vcpu_info(%rbx),%rax
         pushq COMPAT_VCPUINFO_upcall_mask(%rax)
-        testb $TBF_INTERRUPT,%cl
+        testb $TBF_INTERRUPT,TRAPBOUNCE_flags(%rdx)
         setnz %ch                       # TBF_INTERRUPT -> set upcall mask
         orb   %ch,COMPAT_VCPUINFO_upcall_mask(%rax)
         popq  %rax
@@ -284,7 +283,7 @@ compat_create_bounce_frame:
 .Lft6:  movl  %eax,%fs:2*4(%rsi)        # EFLAGS
         movl  UREGS_rip+8(%rsp),%eax
 .Lft7:  movl  %eax,%fs:(%rsi)           # EIP
-        testb $TBF_EXCEPTION_ERRCODE,%cl
+        testb $TBF_EXCEPTION_ERRCODE,TRAPBOUNCE_flags(%rdx)
         jz    1f
         subl  $4,%esi
         movl  TRAPBOUNCE_error_code(%rdx),%eax
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index dd7f114..221de01 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -343,7 +343,6 @@ UNLIKELY_START(g, create_bounce_frame_bad_sp)
         lea   UNLIKELY_DISPATCH_LABEL(create_bounce_frame_bad_sp)(%rip), %rdi
         jmp   asm_domain_crash_synchronous  /* Does not return */
 __UNLIKELY_END(create_bounce_frame_bad_sp)
-        movb  TRAPBOUNCE_flags(%rdx),%cl
         subq  $40,%rsi
         movq  UREGS_ss+8(%rsp),%rax
         ASM_STAC
@@ -352,7 +351,7 @@ __UNLIKELY_END(create_bounce_frame_bad_sp)
 .Lft3:  movq  %rax,24(%rsi)             # RSP
         movq  VCPU_vcpu_info(%rbx),%rax
         pushq VCPUINFO_upcall_mask(%rax)
-        testb $TBF_INTERRUPT,%cl
+        testb $TBF_INTERRUPT,TRAPBOUNCE_flags(%rdx)
         setnz %ch                       # TBF_INTERRUPT -> set upcall mask
         orb   %ch,VCPUINFO_upcall_mask(%rax)
         popq  %rax
@@ -369,7 +368,7 @@ __UNLIKELY_END(create_bounce_frame_bad_sp)
 .Lft5:  movq  %rax,16(%rsi)             # RFLAGS
         movq  UREGS_rip+8(%rsp),%rax
 .Lft6:  movq  %rax,(%rsi)               # RIP
-        testb $TBF_EXCEPTION_ERRCODE,%cl
+        testb $TBF_EXCEPTION_ERRCODE,TRAPBOUNCE_flags(%rdx)
         jz    1f
         subq  $8,%rsi
         movl  TRAPBOUNCE_error_code(%rdx),%eax
-- 
2.1.4


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