linux-kernel - Re: [RFC PATCH v3 10/20] Add support to access boot related data in the clear

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Message-ID: <d25de4d7-ae6f-b701-8ae1-0a39fa02a9b0@amd.com>
Date:   Mon, 14 Nov 2016 10:24:14 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     "Kani, Toshimitsu" <toshi.kani@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
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        "corbet@....net" <corbet@....net>,
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Subject: Re: [RFC PATCH v3 10/20] Add support to access boot related data in
 the clear

On 11/11/2016 10:17 AM, Kani, Toshimitsu wrote:
> On Wed, 2016-11-09 at 18:36 -0600, Tom Lendacky wrote:
>> Boot data (such as EFI related data) is not encrypted when the system
>> is booted and needs to be accessed unencrypted.  Add support to apply
>> the proper attributes to the EFI page tables and to the
>> early_memremap and memremap APIs to identify the type of data being
>> accessed so that the proper encryption attribute can be applied.
>  :
>> +static bool memremap_apply_encryption(resource_size_t phys_addr,
>> +				      unsigned long size)
>> +{
>> +	/* SME is not active, just return true */
>> +	if (!sme_me_mask)
>> +		return true;
>> +
>> +	/* Check if the address is part of the setup data */
>> +	if (memremap_setup_data(phys_addr, size))
>> +		return false;
>> +
>> +	/* Check if the address is part of EFI boot/runtime data */
>> +	switch (efi_mem_type(phys_addr)) {
>> +	case EFI_BOOT_SERVICES_DATA:
>> +	case EFI_RUNTIME_SERVICES_DATA:
>> +		return false;
>> +	}
>> +
>> +	/* Check if the address is outside kernel usable area */
>> +	switch (e820_get_entry_type(phys_addr, phys_addr + size -
>> 1)) {
>> +	case E820_RESERVED:
>> +	case E820_ACPI:
>> +	case E820_NVS:
>> +	case E820_UNUSABLE:
>> +		return false;
>> +	}
>> +
>> +	return true;
>> +}
> 
> Are you supporting encryption for E820_PMEM ranges?  If so, this
> encryption will persist across a reboot and does not need to be
> encrypted again, right?  Also, how do you keep a same key across a
> reboot?

The key will change across a reboot... so I need to look into this
more for memory that isn't used as traditional system ram.

Thanks,
Tom

> 
> Thanks,
> -Toshi
>