On Tue, 2024-11-05 at 10:00 +0000, Huang, Kai wrote: > On Sun, 2024-11-03 at 05:35 +0000, David Woodhouse wrote: > > From: David Woodhouse <dwmw@xxxxxxxxxxxx> > > > > Add more comments explaining what each register contains, and save the > > preserve_context flag to a non-clobbered register sooner, to keep things > > simpler. > > > > Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> > > --- > > arch/x86/kernel/relocate_kernel_64.S | 17 +++++++++++++---- > > 1 file changed, 13 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S > > index e9e88c342f75..c065806884f8 100644 > > --- a/arch/x86/kernel/relocate_kernel_64.S > > +++ b/arch/x86/kernel/relocate_kernel_64.S > > @@ -100,6 +100,9 @@ SYM_CODE_START_NOALIGN(relocate_kernel) > > movq %r10, CP_PA_SWAP_PAGE(%r11) > > movq %rdi, CP_PA_BACKUP_PAGES_MAP(%r11) > > > > + /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */ > > + movq %rcx, %r11 > > + > > Seems moving this here won't break anything. From functionality's perspective > there's no need move this here, but fine to me since the move is needed for the > sake of adding the comment (below) to identity_mapped. I believe I did actually use %rcx in the debug code I added later, didn't I? > > /* Switch to the identity mapped page tables */ > > movq %r9, %cr3 > > > > @@ -116,6 +119,13 @@ SYM_CODE_END(relocate_kernel) > > > > SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) > > UNWIND_HINT_END_OF_STACK > > + /* > > + * %rdi indirection page > > + * %rdx start address > > + * %r11 preserve_context > > + * %r12 host_mem_enc_active > > + */ > > + > > I think adding this comment is the main purpose of this patch. Since we have > listed 4 regs in the comment, how about also add an entry for %r13? > > Something like: > > %r13 original CR4 when relocate_kernel() is invoked > > Yeah this is kinda mentioned in later code but it seems it's more complete if we > also mention %r13 here. Ack, I'll add that too. Thanks. > Anyway, I suppose adding this comment is kinda helpful, so: > > Acked-by: Kai Huang <kai.huang@xxxxxxxxx> >
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