linux-kernel - Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with cc_platform

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Date:   Tue, 21 Sep 2021 12:04:58 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-graphics-maintainer@...are.com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 5/8] x86/sme: Replace occurrences of sme_active() with
 cc_platform_has()

On 9/20/21 2:23 PM, Kirill A. Shutemov wrote:
> 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.

Looks like instrumentation during early boot. I worked with Boris offline 
to exclude arch/x86/kernel/cc_platform.c from some of the instrumentation 
and that allowed an allyesconfig to boot.

Thanks,
Tom

> 
> 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.
>