[xen master] x86/entry: Rework the comment about SYSCALL and DF

[patchbot@xxxxxxx]

commit 0ad41c61927d8a49518121c3d6e43a184c2117b1
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Aug 27 10:51:38 2025 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Dec 5 23:00:32 2025 +0000

    x86/entry: Rework the comment about SYSCALL and DF
    
    It's soon going to be needed in a second location.
    
    Right now it's misleading saying that nothing else would be cleared.  It's
    missing the more important point that SYSCALLs are treated like all other
    interrupts and exceptions, and undergo normal flags handling there.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/x86_64/entry.S | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 01b431793b..ca446c6ff0 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -39,10 +39,9 @@ FUNC_LOCAL(switch_to_kernel)
         leal  (,%rcx,TBF_INTERRUPT),%ecx
 
         /*
-         * The PV ABI hardcodes the (guest-inaccessible and virtual)
-         * SYSCALL_MASK MSR such that DF (and nothing else) would be cleared.
-         * Note that the equivalent of IF (VGCF_syscall_disables_events) is
-         * dealt with separately above.
+         * The PV ABI, given no virtual SYSCALL_MASK, hardcodes that DF is
+         * cleared.  Other flags are handled in the same way as interrupts and
+         * exceptions in create_bounce_frame().
          */
         mov   $~X86_EFLAGS_DF, %esi
 
--
generated by git-patchbot for /home/xen/git/xen.git#master