Messages in this thread | | | Date | Wed, 21 Jun 2017 09:16:05 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v7 08/36] x86/mm: Add support to enable SME in early boot processing |
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On Fri, 16 Jun 2017, Tom Lendacky wrote: > diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h > index a105796..988b336 100644 > --- a/arch/x86/include/asm/mem_encrypt.h > +++ b/arch/x86/include/asm/mem_encrypt.h > @@ -15,16 +15,24 @@ > > #ifndef __ASSEMBLY__ > > +#include <linux/init.h> > + > #ifdef CONFIG_AMD_MEM_ENCRYPT > > extern unsigned long sme_me_mask; > > +void __init sme_enable(void); > + > #else /* !CONFIG_AMD_MEM_ENCRYPT */ > > #define sme_me_mask 0UL > > +static inline void __init sme_enable(void) { } > + > #endif /* CONFIG_AMD_MEM_ENCRYPT */ > > +unsigned long sme_get_me_mask(void);
Why is this an unconditional function? Isn't the mask simply 0 when the MEM ENCRYPT support is disabled?
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 6225550..ef12729 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -78,7 +78,29 @@ startup_64: > call __startup_64 > popq %rsi > > - movq $(early_top_pgt - __START_KERNEL_map), %rax > + /* > + * Encrypt the kernel if SME is active. > + * The real_mode_data address is in %rsi and that register can be > + * clobbered by the called function so be sure to save it. > + */ > + push %rsi > + call sme_encrypt_kernel > + pop %rsi
That does not make any sense. Neither the call to sme_encrypt_kernel() nor the following call to sme_get_me_mask().
__startup_64() is already C code, so why can't you simply call that from __startup_64() in C and return the mask from there?
> @@ -98,7 +120,20 @@ ENTRY(secondary_startup_64) > /* Sanitize CPU configuration */ > call verify_cpu > > - movq $(init_top_pgt - __START_KERNEL_map), %rax > + /* > + * Get the SME encryption mask. > + * The encryption mask will be returned in %rax so we do an ADD > + * below to be sure that the encryption mask is part of the > + * value that will stored in %cr3. > + * > + * The real_mode_data address is in %rsi and that register can be > + * clobbered by the called function so be sure to save it. > + */ > + push %rsi > + call sme_get_me_mask > + pop %rsi
Do we really need a call here? The mask is established at this point, so it's either 0 when the encryption stuff is not compiled in or it can be retrieved from a variable which is accessible at this point.
> + > + addq $(init_top_pgt - __START_KERNEL_map), %rax > 1: > > /* Enable PAE mode, PGE and LA57 */
Thanks,
tglx
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