Messages in this thread | | | Date | Wed, 18 Oct 2023 12:20:15 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/2] x86/sme: Mark the code as __head in mem_encrypt_identity.c |
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* Hou Wenlong <houwenlong.hwl@antgroup.com> wrote:
> On Tue, Oct 17, 2023 at 08:52:46PM +0800, Ingo Molnar wrote: > > > > * Hou Wenlong <houwenlong.hwl@antgroup.com> 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@antgroup.com> > > > --- > > > 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.
The right solution at that point is to make <asm/init.h> self-contained...
> 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.
When exporting a localized definition you should consider namespace collisions - the name '__head' is way too generic, no wonder it caused problems elsewhere.
I'd suggest naming it __init_head or so, but still keep it in a x86-only header.
I presume keeping it all in the separate section and widening its usage has a specific purpose? Please outline that in the changelog as well.
Ie. instead of mechanical patches that try to follow existing patterns cargo-cult style, this area of x86 code requires well-argued, well thought out patches that show background knowledge of the area.
Thanks,
Ingo
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