Re: [PATCH 2/2] x86/sme: Mark the code as __head in mem_encrypt_identity.c

[Hou Wenlong]

On Tue, Oct 17, 2023 at 08:52:46PM +0800, Ingo Molnar wrote:
> 
> * Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx> wrote:
> 
> > The functions sme_enable() and sme_encrypt_kernel() are only called by
> > the head code which runs in identity virtual address. Therefore, it's
> > better to mark them as __head as well.
> > 
> > Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
> > ---
> >  arch/x86/include/asm/mem_encrypt.h |  8 ++++----
> >  arch/x86/mm/mem_encrypt_identity.c | 27 ++++++++++++++-------------
> >  2 files changed, 18 insertions(+), 17 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> > index 359ada486fa9..48469e22a75e 100644
> > --- a/arch/x86/include/asm/mem_encrypt.h
> > +++ b/arch/x86/include/asm/mem_encrypt.h
> > @@ -46,8 +46,8 @@ void __init sme_unmap_bootdata(char *real_mode_data);
> >  
> >  void __init sme_early_init(void);
> >  
> > -void __init sme_encrypt_kernel(struct boot_params *bp);
> > -void __init sme_enable(struct boot_params *bp);
> > +void sme_encrypt_kernel(struct boot_params *bp);
> > +void sme_enable(struct boot_params *bp);
> >  
> >  int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
> >  int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
> > @@ -75,8 +75,8 @@ static inline void __init sme_unmap_bootdata(char *real_mode_data) { }
> >  
> >  static inline void __init sme_early_init(void) { }
> >  
> > -static inline void __init sme_encrypt_kernel(struct boot_params *bp) { }
> > -static inline void __init sme_enable(struct boot_params *bp) { }
> > +static inline void sme_encrypt_kernel(struct boot_params *bp) { }
> > +static inline void sme_enable(struct boot_params *bp) { }
> 
> So I think we should preserve the previous convention of marking functions 
> __init in the header-declaration and at the definition site as well, and do 
> the same with __head as well?
> 
Hi Ingo,

I tried to include <asm/init.h> into <asm/mem_encrypt.h> and mark the
function declaration as __head, but it resulted in a build failure. This
is because <asm/init.h> is not self-contained; the type "pgd_t" is
defined in <asm/pgtable_types.h>, which includes <asm/mem_encrypt.h>,
leading to mutual inclusion of header files. To avoid the issue of
complicated header file inclusion, I removed the annotation from the
function declaration.

Actually, initially, I noticed that the __init definition is in
<linux/init.h>, so I first placed the __head definition in
<linux/init.h> as well. However, this conflicted with the local variable
in the "list_next_or_null_rcu" macro in <linux/rculist.h>. Then I
realized that __head was only used in x86, so I made the decision to put
it in the architecture-specific header. Considering simplicity, I chose
to put the definition in <asm/init.h>. I also attempted to put the
definition in other headers such as <asm/boot.h> and
<asm/bootparam_utils.h>, and included them in <asm/mem_encrypt.h>, but
the build still failed.

Thanks!

> Thanks,
> 
> 	Ingo