linux-kernel - Re: [Part1 PATCH v4 14/17] x86: Add support for changing memory encryption attribute in early boot

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Date:   Sun, 17 Sep 2017 17:25:46 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [Part1 PATCH v4 14/17] x86: Add support for changing memory
 encryption attribute in early boot

On Sat, Sep 16, 2017 at 07:34:15AM -0500, Brijesh Singh wrote:
> Some KVM-specific custom MSRs share the guest physical address with the
> hypervisor in early boot. When SEV is active, the shared physical address
> must be mapped with memory encryption attribute cleared so that both
> hypervisor and guest can access the data.
> 
> Add APIs to change the memory encryption attribute in early boot code.
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/include/asm/mem_encrypt.h |  17 ++++++
>  arch/x86/mm/mem_encrypt.c          | 121 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 138 insertions(+)
> 
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 2b024741bce9..21b9d8fc8293 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -42,6 +42,11 @@ void __init sme_early_init(void);
>  void __init sme_encrypt_kernel(void);
>  void __init sme_enable(struct boot_params *bp);
>  
> +int __init early_set_memory_decrypted(resource_size_t paddr,
> +				      unsigned long size);
> +int __init early_set_memory_encrypted(resource_size_t paddr,
> +				      unsigned long size);
> +

Let those stick out on a single line.

>  /* Architecture __weak replacement functions */
>  void __init mem_encrypt_init(void);
>  
> @@ -70,6 +75,18 @@ static inline void __init sme_enable(struct boot_params *bp) { }
>  static inline bool sme_active(void) { return false; }
>  static inline bool sev_active(void) { return false; }
>  
> +static inline int __init early_set_memory_decrypted(resource_size_t paddr,
> +						    unsigned long size)
> +{
> +	return 0;
> +}
> +
> +static inline int __init early_set_memory_encrypted(resource_size_t paddr,
> +						    unsigned long size)
> +{
> +	return 0;
> +}

Yeah, let's save some screen real-estate like this:

static inline int __init
early_set_memory_decrypted(resource_size_t paddr, unsigned long size)	{ return 0; }
static inline int __init
early_set_memory_encrypted(resource_size_t paddr, unsigned long size)	{ return 0; }

With that fixed:

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--