linux-kernel - Re: [PATCH v4 04/15] x86/sev: Check for the presence of an SVSM in the SNP Secrets page

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Date: Wed, 22 May 2024 11:15:28 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, linux-coco@...ts.linux.dev,
 svsm-devel@...onut-svsm.dev, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Dan Williams <dan.j.williams@...el.com>, Michael Roth
 <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>
Subject: Re: [PATCH v4 04/15] x86/sev: Check for the presence of an SVSM in
 the SNP Secrets page

On 5/22/24 10:27, Borislav Petkov wrote:
> On Mon, May 20, 2024 at 08:57:43AM -0500, Tom Lendacky wrote:
>> So this will be a new shared directory in the top level include directory
>> (as PAGE_ALIGNED is defined in include/linux/mm.h), not just in the
>> arch/x86/include directory like the others (io.h, msr.h and tdx.h). Is that
>> what you want?
> 
> You can actually do this - it is a lot easier and still clean:
> 
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index cb771b380a6b..5ee53a7a060e 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -12,7 +12,6 @@
>    */
>   #include "misc.h"
>   
> -#include <linux/mm.h>
>   #include <asm/bootparam.h>
>   #include <asm/pgtable_types.h>
>   #include <asm/sev.h>
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 46ea4e5e118a..bd4bbb30ef0c 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -1329,7 +1329,12 @@ static void __head setup_svsm_ca(const struct cc_blob_sev_info *cc_info)
>   	vmpl = secrets_page->svsm_guest_vmpl;
>   
>   	caa = secrets_page->svsm_caa;
> -	if (!PAGE_ALIGNED(caa))
> +
> +	/*
> +	 * Open-code PAGE_ALIGNED() to avoid pulling in the world and
> +	 * more by including linux/mm.h.
> +	 */
> +	if (caa & (PAGE_SIZE - 1))

Or what I originally proposed:

	if (!IS_ALIGNED(caa, PAGE_SIZE))

Which also works without including mm.h.

Thanks,
Tom

>   		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_CAA);
>   
>   	/*
>