linux-kernel - Re: [PATCH v8 02/40] x86/sev: detect/setup SEV/SME features earlier in boot

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Message-ID: <YbfK+tQ40+z9BUo+@dt>
Date:   Mon, 13 Dec 2021 16:36:42 -0600
From:   Venu Busireddy <venu.busireddy@...cle.com>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v8 02/40] x86/sev: detect/setup SEV/SME features earlier
 in boot

On 2021-12-10 09:42:54 -0600, Brijesh Singh wrote:
> From: Michael Roth <michael.roth@....com>
> 
> sme_enable() handles feature detection for both SEV and SME. Future
> patches will also use it for SEV-SNP feature detection/setup, which
> will need to be done immediately after the first #VC handler is set up.
> Move it now in preparation.
> 
> Signed-off-by: Michael Roth <michael.roth@....com>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>

Reviewed-by: Venu Busireddy <venu.busireddy@...cle.com>

> ---
>  arch/x86/kernel/head64.c  |  3 ---
>  arch/x86/kernel/head_64.S | 13 +++++++++++++
>  2 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 3be9dd213dad..b01f64e8389b 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -192,9 +192,6 @@ unsigned long __head __startup_64(unsigned long physaddr,
>  	if (load_delta & ~PMD_PAGE_MASK)
>  		for (;;);
>  
> -	/* Activate Secure Memory Encryption (SME) if supported and enabled */
> -	sme_enable(bp);
> -
>  	/* Include the SME encryption mask in the fixup value */
>  	load_delta += sme_get_me_mask();
>  
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index d8b3ebd2bb85..99de8fd461e8 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -69,6 +69,19 @@ SYM_CODE_START_NOALIGN(startup_64)
>  	call	startup_64_setup_env
>  	popq	%rsi
>  
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> +	/*
> +	 * Activate SEV/SME memory encryption if supported/enabled. This needs to
> +	 * be done now, since this also includes setup of the SEV-SNP CPUID table,
> +	 * which needs to be done before any CPUID instructions are executed in
> +	 * subsequent code.
> +	 */
> +	movq	%rsi, %rdi
> +	pushq	%rsi
> +	call	sme_enable
> +	popq	%rsi
> +#endif
> +
>  	/* Now switch to __KERNEL_CS so IRET works reliably */
>  	pushq	$__KERNEL_CS
>  	leaq	.Lon_kernel_cs(%rip), %rax
> -- 
> 2.25.1
>