linux-kernel - Re: [RFC PATCH v1 15/18] x86: Enable memory encryption on the APs

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Date:	Mon, 2 May 2016 10:10:24 +1200
From:	"Huang, Kai" <kai.huang@...ux.intel.com>
To:	Tom Lendacky <thomas.lendacky@....com>, linux-arch@...r.kernel.org,
	linux-efi@...r.kernel.org, kvm@...r.kernel.org,
	linux-doc@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
	linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:	Radim Krčmář <rkrcmar@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	Jonathan Corbet <corbet@....net>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Joerg Roedel <joro@...tes.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Alexander Potapenko <glider@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v1 15/18] x86: Enable memory encryption on the APs



On 4/27/2016 10:58 AM, Tom Lendacky wrote:
> Add support to set the memory encryption enable flag on the APs during
> realmode initialization. When an AP is started it checks this flag, and
> if set, enables memory encryption on its core.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/include/asm/msr-index.h     |    2 ++
>  arch/x86/include/asm/realmode.h      |   12 ++++++++++++
>  arch/x86/realmode/init.c             |    4 ++++
>  arch/x86/realmode/rm/trampoline_64.S |   14 ++++++++++++++
>  4 files changed, 32 insertions(+)
>
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 94555b4..b73182b 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -349,6 +349,8 @@
>  #define MSR_K8_TOP_MEM1			0xc001001a
>  #define MSR_K8_TOP_MEM2			0xc001001d
>  #define MSR_K8_SYSCFG			0xc0010010
> +#define MSR_K8_SYSCFG_MEM_ENCRYPT_BIT	23
> +#define MSR_K8_SYSCFG_MEM_ENCRYPT	(1ULL << MSR_K8_SYSCFG_MEM_ENCRYPT_BIT)
>  #define MSR_K8_INT_PENDING_MSG		0xc0010055
>  /* C1E active bits in int pending message */
>  #define K8_INTP_C1E_ACTIVE_MASK		0x18000000
> diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
> index 9c6b890..e24d2ec 100644
> --- a/arch/x86/include/asm/realmode.h
> +++ b/arch/x86/include/asm/realmode.h
> @@ -1,6 +1,15 @@
>  #ifndef _ARCH_X86_REALMODE_H
>  #define _ARCH_X86_REALMODE_H
>
> +/*
> + * Flag bit definitions for use with the flags field of the trampoline header
> + * when configured for X86_64
> + */
> +#define TH_FLAGS_MEM_ENCRYPT_BIT	0
> +#define TH_FLAGS_MEM_ENCRYPT		(1ULL << TH_FLAGS_MEM_ENCRYPT_BIT)

Would mind change it to a more vendor specific name, such as 
AMD_MEM_ENCRYPT, or SME_MEM_ENCRYPT?

> +
> +#ifndef __ASSEMBLY__
> +
>  #include <linux/types.h>
>  #include <asm/io.h>
>
> @@ -38,6 +47,7 @@ struct trampoline_header {
>  	u64 start;
>  	u64 efer;
>  	u32 cr4;
> +	u32 flags;
>  #endif
>  };
>
> @@ -61,4 +71,6 @@ extern unsigned char secondary_startup_64[];
>  void reserve_real_mode(void);
>  void setup_real_mode(void);
>
> +#endif /* __ASSEMBLY__ */
> +
>  #endif /* _ARCH_X86_REALMODE_H */
> diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
> index 85b145c..657532b 100644
> --- a/arch/x86/realmode/init.c
> +++ b/arch/x86/realmode/init.c
> @@ -84,6 +84,10 @@ void __init setup_real_mode(void)
>  	trampoline_cr4_features = &trampoline_header->cr4;
>  	*trampoline_cr4_features = __read_cr4();
>
> +	trampoline_header->flags = 0;
> +	if (sme_me_mask)
> +		trampoline_header->flags |= TH_FLAGS_MEM_ENCRYPT;
> +
>  	trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
>  	trampoline_pgd[0] = init_level4_pgt[pgd_index(__PAGE_OFFSET)].pgd;
>  	trampoline_pgd[511] = init_level4_pgt[511].pgd;
> diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S
> index dac7b20..8d84167 100644
> --- a/arch/x86/realmode/rm/trampoline_64.S
> +++ b/arch/x86/realmode/rm/trampoline_64.S
> @@ -30,6 +30,7 @@
>  #include <asm/msr.h>
>  #include <asm/segment.h>
>  #include <asm/processor-flags.h>
> +#include <asm/realmode.h>
>  #include "realmode.h"
>
>  	.text
> @@ -109,6 +110,18 @@ ENTRY(startup_32)
>  	movl	$(X86_CR0_PG | X86_CR0_WP | X86_CR0_PE), %eax
>  	movl	%eax, %cr0
>
> +	# Check for and enable memory encryption support
> +	movl	pa_tr_flags, %eax
> +	bt	$TH_FLAGS_MEM_ENCRYPT_BIT, pa_tr_flags

pa_tr_flags -> %eax ? Otherwise looks the previous line is useless.

Thanks,
-Kai

> +	jnc	.Ldone
> +	movl	$MSR_K8_SYSCFG, %ecx
> +	rdmsr
> +	bt	$MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax
> +	jc	.Ldone
> +	bts	$MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax
> +	wrmsr
> +.Ldone:
> +
>  	/*
>  	 * At this point we're in long mode but in 32bit compatibility mode
>  	 * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
> @@ -147,6 +160,7 @@ GLOBAL(trampoline_header)
>  	tr_start:		.space	8
>  	GLOBAL(tr_efer)		.space	8
>  	GLOBAL(tr_cr4)		.space	4
> +	GLOBAL(tr_flags)	.space	4
>  END(trampoline_header)
>
>  #include "trampoline_common.S"
>
>