On 06/03/2024 1:44 pm, Jan Beulich wrote: > --- a/xen/arch/x86/x86_64/entry.S > +++ b/xen/arch/x86/x86_64/entry.S > @@ -47,12 +55,13 @@ UNLIKELY_START(z, syscall_no_callback) / > testb $4, X86_EXC_UD * TRAPINFO_sizeof + TRAPINFO_flags(%rdi) > setnz %cl > lea TBF_EXCEPTION(, %rcx, TBF_INTERRUPT), %ecx > + or $~0, %esi # don't clear DF
Our predominant comment style is /* */ > UNLIKELY_END(syscall_no_callback) > > movq %rax,TRAPBOUNCE_eip(%rdx) > movb %cl,TRAPBOUNCE_flags(%rdx) > call create_bounce_frame > - andl $~X86_EFLAGS_DF,UREGS_eflags(%rsp) > + and %esi, UREGS_eflags(%rsp) Could we gain a /* Conditionally clear DF */ comment here? Otherwise, Reviewed-by: Andrew Cooper <andrew.coop...@citrix.com> CC Oleksii for 4.19. This fixes a subtle regression in the PV ABI caused by a post-XSA fix a few years ago. It's a low-risk fix to take; while I still don't have an XTF test covering this, the corner case it's changing used to be completely fatal to guests, so it's a corner unused in practice. ~Andrew
