[Xen-devel] [PATCH] x86: fix return value checks of set_guest_{machinecheck, nmi}_trapbounce

["Jan Beulich" <JBeulich@xxxxxxxx>]

Commit 0142064421 ("x86/traps: move set_guest_{machine,nmi}_trapbounce")
converted the functions' return types from int to bool without also
correcting the checks in assembly code: The ABI does not guarantee sub-
32-bit return values to be promoted to 32 bits.

Take the liberty and also adjust the number of spaces used in the compat
code, such that both code sequences end up similar (they already are in
the non-compat case).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
This wants backporting to 4.10.

--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -74,9 +74,9 @@ compat_process_mce:
         testb $1 << VCPU_TRAP_MCE,VCPU_async_exception_mask(%rbx)
         jnz   .Lcompat_test_guest_nmi
         sti
-        movb $0,VCPU_mce_pending(%rbx)
-        call set_guest_machinecheck_trapbounce
-        testl %eax,%eax
+        movb  $0, VCPU_mce_pending(%rbx)
+        call  set_guest_machinecheck_trapbounce
+        test  %al, %al
         jz    compat_test_all_events
         movzbl VCPU_async_exception_mask(%rbx),%edx # save mask for the
         movb %dl,VCPU_mce_old_mask(%rbx)            # iret hypercall
@@ -88,11 +88,11 @@ compat_process_mce:
 /* %rbx: struct vcpu */
 compat_process_nmi:
         testb $1 << VCPU_TRAP_NMI,VCPU_async_exception_mask(%rbx)
-        jnz  compat_test_guest_events
+        jnz   compat_test_guest_events
         sti
-        movb  $0,VCPU_nmi_pending(%rbx)
+        movb  $0, VCPU_nmi_pending(%rbx)
         call  set_guest_nmi_trapbounce
-        testl %eax,%eax
+        test  %al, %al
         jz    compat_test_all_events
         movzbl VCPU_async_exception_mask(%rbx),%edx # save mask for the
         movb %dl,VCPU_nmi_old_mask(%rbx)            # iret hypercall
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -77,7 +77,7 @@ process_mce:
         sti
         movb $0, VCPU_mce_pending(%rbx)
         call set_guest_machinecheck_trapbounce
-        test %eax, %eax
+        test %al, %al
         jz   test_all_events
         movzbl VCPU_async_exception_mask(%rbx), %edx # save mask for the
         movb %dl, VCPU_mce_old_mask(%rbx)            # iret hypercall
@@ -93,7 +93,7 @@ process_nmi:
         sti
         movb $0, VCPU_nmi_pending(%rbx)
         call set_guest_nmi_trapbounce
-        test %eax, %eax
+        test %al, %al
         jz   test_all_events
         movzbl VCPU_async_exception_mask(%rbx), %edx # save mask for the
         movb %dl, VCPU_nmi_old_mask(%rbx)            # iret hypercall




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