Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Cc:     brijesh.singh@amd.com, x86@kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Borislav Petkov <bp@suse.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [PATCH v8 1/2] x86/mm: add .bss..decrypted section to hold shared
 variables
To:     Thomas Gleixner <tglx@linutronix.de>
References: <1536875471-17391-1-git-send-email-brijesh.singh@amd.com>
 <1536875471-17391-2-git-send-email-brijesh.singh@amd.com>
 <alpine.DEB.2.21.1809140122590.1473@nanos.tec.linutronix.de>
From:   Brijesh Singh <brijesh.singh@amd.com>
Message-ID: <a9391cea-bdd5-fdfe-442b-0c9f9699ee49@amd.com>
Date:   Thu, 13 Sep 2018 21:14:47 -0500
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0)
 Gecko/20100101 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.21.1809140122590.1473@nanos.tec.linutronix.de>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Received-SPF: None (protection.outlook.com: amd.com does not designate
 permitted sender hosts)
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Sep 2018 02:14:51.7137 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 8d81cd24-9788-49ee-c062-08d619e7db76
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN7PR12MB2673
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 9/13/18 6:24 PM, Thomas Gleixner wrote:
> On Thu, 13 Sep 2018, Brijesh Singh wrote:
>>  
>> +void __weak mem_encrypt_free_decrypted_mem(void) { }
>> +
>>  void __ref free_initmem(void)
>>  {
>>  	e820__reallocate_tables();
>>  
>> +	mem_encrypt_free_decrypted_mem();
>> +
>>  	free_kernel_image_pages(&__init_begin, &__init_end);
>>  }
>>  
>> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
>> index b2de398..718acdf 100644
>> --- a/arch/x86/mm/mem_encrypt.c
>> +++ b/arch/x86/mm/mem_encrypt.c
>> @@ -348,6 +348,16 @@ bool sev_active(void)
>>  EXPORT_SYMBOL(sev_active);
>>  
>>  /* Architecture __weak replacement functions */
>> +void __init mem_encrypt_free_decrypted_mem(void)
>> +{
>> +	if (mem_encrypt_active())
>> +		return;
> Why?

Hmm, I think we should be able to free the unused memory when memory
encryption is active.
In that case, since memory range was mapped C=0 so we should do
set_memory_encryptyed()
to change from C=0 -> C=1 before freeing it.

>> +
>> +	free_init_pages("unused decrypted",
>> +			(unsigned long)__start_bss_decrypted_unused,
>> +			(unsigned long)__end_bss_decrypted);
> Everything _AFTER_ __start_bss_decrypted_unused _IS_ unused and can be
> freed. No conditional nothing. It's unused in any case.
>
> Thanks,
>
> 	tglx
>
>