Re: [Part1 PATCH v5 12/17] x86/boot: Add early boot support when running with SEV active

[Borislav Petkov]

On Wed, Sep 27, 2017 at 10:13:24AM -0500, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
> 
> Early in the boot process, add checks to determine if the kernel is
> running with Secure Encrypted Virtualization (SEV) active.
> 
> Checking for SEV requires checking that the kernel is running under a
> hypervisor (CPUID 0x00000001, bit 31), that the SEV feature is available
> (CPUID 0x8000001f, bit 1) and then checking a non-interceptable SEV MSR
> (0xc0010131, bit 0).
> 
> This check is required so that during early compressed kernel booting the
> pagetables (both the boot pagetables and KASLR pagetables (if enabled) are
> updated to include the encryption mask so that when the kernel is
> decompressed into encrypted memory, it can boot properly.
> 
> After the kernel is decompressed and continues booting the same logic is
> used to check if SEV is active and set a flag indicating so.  This allows
> us to distinguish between SME and SEV, each of which have unique
> differences in how certain things are handled: e.g. DMA (always bounce
> buffered with SEV) or EFI tables (always access decrypted with SME).
> 
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Laura Abbott <labbott@xxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> ---
>  arch/x86/boot/compressed/Makefile      |   1 +
>  arch/x86/boot/compressed/head_64.S     |  16 +++++
>  arch/x86/boot/compressed/mem_encrypt.S | 120 +++++++++++++++++++++++++++++++++
>  arch/x86/boot/compressed/misc.h        |   2 +
>  arch/x86/boot/compressed/pagetable.c   |   8 ++-
>  arch/x86/include/asm/msr-index.h       |   3 +
>  arch/x86/include/uapi/asm/kvm_para.h   |   1 -
>  arch/x86/mm/mem_encrypt.c              |  50 +++++++++++---
>  8 files changed, 186 insertions(+), 15 deletions(-)
>  create mode 100644 arch/x86/boot/compressed/mem_encrypt.S

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index c301cecd7052..bc6ba4cbe9b4 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -311,7 +311,9 @@ void __init mem_encrypt_init(void)
>  	if (sev_active())
>  		dma_ops = &sev_dma_ops;
>  
> -	pr_info("AMD Secure Memory Encryption (SME) active\n");
> +	pr_info("AMD %s active\n",
> +		sev_active() ? "Secure Encrypted Virtualization (SEV)"
> +			     : "Secure Memory Encryption (SME)");
>  }
>  
>  void swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
> @@ -639,37 +641,63 @@ void __init __nostackprotector sme_enable(struct boot_params *bp)

This function should be renamed to mem_encrypt_enable() or so now that
it enables SEV too. But this is for the TODO list and another, later
patchset.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
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