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
