Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has()

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.kernel.org, Brijesh Singh <brijesh.singh@amd.com>,
	kvm@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	dri-devel@lists.freedesktop.org,
	platform-driver-x86@vger.kernel.org,
	Will Deacon <will@kernel.org>,
	linux-s390@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
	x86@kernel.org, amd-gfx@lists.freedesktop.org,
	Christoph Hellwig <hch@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	linux-graphics-maintainer@vmware.com,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform_has()
Date: Mon, 20 Sep 2021 22:23:41 +0300	[thread overview]
Message-ID: <20210920192341.maue7db4lcbdn46x@box.shutemov.name> (raw)
In-Reply-To: <367624d43d35d61d5c97a8b289d9ddae223636e9.1631141919.git.thomas.lendacky@amd.com>

On Wed, Sep 08, 2021 at 05:58:36PM -0500, Tom Lendacky wrote:
> diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
> index 470b20208430..eff4d19f9cb4 100644
> --- a/arch/x86/mm/mem_encrypt_identity.c
> +++ b/arch/x86/mm/mem_encrypt_identity.c
> @@ -30,6 +30,7 @@
>  #include <linux/kernel.h>
>  #include <linux/mm.h>
>  #include <linux/mem_encrypt.h>
> +#include <linux/cc_platform.h>
>  
>  #include <asm/setup.h>
>  #include <asm/sections.h>
> @@ -287,7 +288,7 @@ void __init sme_encrypt_kernel(struct boot_params *bp)
>  	unsigned long pgtable_area_len;
>  	unsigned long decrypted_base;
>  
> -	if (!sme_active())
> +	if (!cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
>  		return;
>  
>  	/*

This change break boot for me (in KVM on Intel host). It only reproduces
with allyesconfig. More reasonable config works fine, but I didn't try to
find exact cause in config.

Convertion to cc_platform_has() in __startup_64() in 8/8 has the same
effect.

I believe it caused by sme_me_mask access from __startup_64() without
fixup_pointer() magic. I think __startup_64() requires special treatement
and we should avoid cc_platform_has() there (or have a special version of
the helper). Note that only AMD requires these cc_platform_has() to return
true.

-- 
 Kirill A. Shutemov
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