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 17:27:12 +0200
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
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 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))
 		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_CAA);
 
 	/*

-- 
Regards/Gruss,
    Boris.

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