From: Brijesh Singh <brijesh.singh@amd.com>
To: Thomas Gleixner <tglx@linutronix.de>
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>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH v8 1/2] x86/mm: add .bss..decrypted section to hold shared variables
Date: Thu, 13 Sep 2018 21:14:47 -0500 [thread overview]
Message-ID: <a9391cea-bdd5-fdfe-442b-0c9f9699ee49@amd.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1809140122590.1473@nanos.tec.linutronix.de>
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
>
>
next prev parent reply other threads:[~2018-09-14 2:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-13 21:51 [PATCH v8 0/2] x86: Fix SEV guest regression Brijesh Singh
2018-09-13 21:51 ` [PATCH v8 1/2] x86/mm: add .bss..decrypted section to hold shared variables Brijesh Singh
2018-09-13 23:24 ` Thomas Gleixner
2018-09-14 2:14 ` Brijesh Singh [this message]
2018-09-14 7:10 ` Borislav Petkov
2018-09-14 11:58 ` Brijesh Singh
2018-09-14 12:17 ` Thomas Gleixner
2018-09-14 14:12 ` Borislav Petkov
2018-09-14 14:27 ` Brijesh Singh
2018-09-14 14:45 ` Borislav Petkov
2018-09-14 14:50 ` Tom Lendacky
2018-09-14 14:55 ` Thomas Gleixner
2018-09-13 21:51 ` [PATCH v8 2/2] x86/kvm: use __bss_decrypted attribute in " Brijesh Singh
2018-09-13 23:31 ` Thomas Gleixner
2018-09-14 0:25 ` kbuild test robot
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