From: Tom Lendacky <thomas.lendacky@amd.com>
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org,
kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
linux-mm@kvack.org, iommu@lists.linux-foundation.org,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Jonathan Corbet" <corbet@lwn.net>,
"Joerg Roedel" <joro@8bytes.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"Andrey Ryabinin" <aryabinin@virtuozzo.com>,
"Alexander Potapenko" <glider@google.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Dmitry Vyukov" <dvyukov@google.com>
Subject: Re: [RFC PATCH v1 10/18] x86/efi: Access EFI related tables in the clear
Date: Wed, 15 Jun 2016 08:17:21 -0500 [thread overview]
Message-ID: <57615561.4090502@amd.com> (raw)
In-Reply-To: <20160613135110.GC2658@codeblueprint.co.uk>
On 06/13/2016 08:51 AM, Matt Fleming wrote:
> On Thu, 09 Jun, at 01:33:30PM, Tom Lendacky wrote:
>>
>> I was trying to play it safe here, but as you say, the firmware should
>> be using our page tables so we can get rid of this call. The problem
>> will actually be if we transition to a 32-bit efi. The encryption bit
>> will be lost in cr3 and so the pgd table will have to be un-encrypted.
>> The entries in the pgd can have the encryption bit set so I would only
>> need to worry about the pgd itself. I'll have to update the
>> efi_alloc_page_tables routine.
>
> Interesting, I hadn't expected 32-bit EFI to be an option for
> platforms with the SME technology. I'd assumed we could just ignore
> that.
We may be able to do that.
>
> Are you saying that the encryption bit isn't supported in 32-bit
> compatibility mode? We don't do a "full" switch to 32-bit protected
> mode when in mixed mode, just load a 32-bit code segment descriptor.
> The page tables are not modified at all.
The encryption bit is supported in 32-bit compatibility mode and since
we're not doing the "full" switch the cr3 register will remain as a
64-bit register so we can leave the pgd table encrypted.
>
>> The encryption bit in the cr3 register will indicate if the pgd table
>> is encrypted or not. Based on my comment above about the pgd having
>> to be un-encrypted in case we have to transition to 32-bit efi, this
>> can be removed.
>
> I'm not (yet) sure that the pgd needs to be unencrypted for 32-bit EFI
> when running a 64-bit kernel. In the AMD Programmer's Manual, Section
> 7.10.3 Operating Modes seems to indicate that running encrypted should
> work fine.
>
>> I'll look into this a bit more. From looking at it I don't want the
>> _PAGE_ENC bit set for the memmap unless it gets re-allocated (which
>> I missed in these patches). Let me see what I can do with this.
>
> I don't understand your comment about re-allocating the memmap.
>
> The kernel builds its own EFI memory map at runtime, initially based
> on the memory map provided by the firmware. We always allocate a new
> memory map.
Sorry, I mis-interpreted the efi_map_regions function/loop and see
that the memmap is always allocated by the kernel.
>
> In efi_setup_page_tables() we're building our own page tables, which
> should be encrypted, and mapping EFI regions described by the memmap
> into those page tables.
>
> So unless we're mapping an MMIO region (in which case _PAGE_PCD is set
> in @flags for kernel_map_pages_in_pgd()) I would expect _PAGE_ENC to
> be set.
>
>> I'll look further into this, but I saw that this area of virtual memory
>> was mapped un-encrypted and after freeing the boot services the
>> mappings were somehow reused as un-encrypted for DMA which assumes
>> (unless using swiotlb) encrypted. This resulted in DMA data being
>> transferred in as encrypted and then accessed un-encrypted.
>
> That the mappings were re-used isn't a surprise.
>
> efi_free_boot_services() lifts the reservation that was put in place
> during efi_reserve_boot_services() and releases the pages to the
> kernel's memory allocators.
>
> What is surprising is that they were marked unencrypted at all.
> There's nothing special about these pages as far as the __va() region
> is concerned.
Right, let me keep looking into this to see if I can pin down what
was (or is) happening.
Thanks,
Tom
>
next prev parent reply other threads:[~2016-06-15 13:32 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 22:55 [RFC PATCH v1 00/18] x86: Secure Memory Encryption (AMD) Tom Lendacky
2016-03-22 13:00 ` Pavel Machek
2016-04-27 14:05 ` Borislav Petkov
2016-04-27 14:30 ` Pavel Machek
2016-04-27 14:39 ` Borislav Petkov
2016-04-27 14:58 ` Pavel Machek
2016-04-27 15:47 ` Pavel Machek
2016-04-27 14:21 ` Tom Lendacky
2016-04-26 22:56 ` [RFC PATCH v1 01/18] x86: Set the write-protect cache mode for AMD processors Tom Lendacky
2016-04-27 14:33 ` Andy Lutomirski
2016-04-27 14:44 ` Tom Lendacky
2016-04-27 14:47 ` Andy Lutomirski
2016-04-27 15:05 ` Tom Lendacky
2016-04-27 15:12 ` Andy Lutomirski
2016-04-27 15:31 ` Borislav Petkov
2016-04-27 15:34 ` Andy Lutomirski
2016-04-26 22:56 ` [RFC PATCH v1 02/18] x86: Secure Memory Encryption (SME) build enablement Tom Lendacky
2016-03-22 13:01 ` Pavel Machek
2016-04-27 15:17 ` Tom Lendacky
2016-04-27 15:30 ` Pavel Machek
2016-04-27 15:41 ` Borislav Petkov
2016-04-27 16:41 ` Pavel Machek
2016-04-27 17:07 ` Robin Murphy
2016-04-27 17:12 ` Borislav Petkov
2016-04-26 22:56 ` [RFC PATCH v1 03/18] x86: Secure Memory Encryption (SME) support Tom Lendacky
2016-03-22 13:03 ` Pavel Machek
2016-04-27 16:20 ` Tom Lendacky
2016-04-26 22:56 ` [RFC PATCH v1 04/18] x86: Add the Secure Memory Encryption cpu feature Tom Lendacky
2016-04-26 22:56 ` [RFC PATCH v1 05/18] x86: Handle reduction in physical address size with SME Tom Lendacky
2016-04-26 22:56 ` [RFC PATCH v1 06/18] x86: Provide general kernel support for memory encryption Tom Lendacky
2016-04-26 22:57 ` [RFC PATCH v1 07/18] x86: Extend the early_memmap support with additional attrs Tom Lendacky
2016-04-26 22:57 ` [RFC PATCH v1 08/18] x86: Add support for early encryption/decryption of memory Tom Lendacky
2016-04-26 22:57 ` [RFC PATCH v1 09/18] x86: Insure that memory areas are encrypted when possible Tom Lendacky
2016-04-26 22:57 ` [RFC PATCH v1 10/18] x86/efi: Access EFI related tables in the clear Tom Lendacky
2016-05-10 13:43 ` Matt Fleming
2016-05-10 13:57 ` Borislav Petkov
2016-05-12 18:20 ` Tom Lendacky
2016-05-24 14:54 ` Tom Lendacky
2016-05-25 16:09 ` Daniel Kiper
2016-05-25 19:30 ` Matt Fleming
2016-05-26 13:45 ` Tom Lendacky
2016-06-08 10:07 ` Matt Fleming
2016-06-09 16:16 ` Tom Lendacky
2016-06-13 12:03 ` Matt Fleming
2016-06-13 12:34 ` Matt Fleming
2016-06-13 15:16 ` Tom Lendacky
2016-06-08 11:18 ` Matt Fleming
2016-06-09 18:33 ` Tom Lendacky
2016-06-13 13:51 ` Matt Fleming
2016-06-15 13:17 ` Tom Lendacky [this message]
2016-06-16 14:38 ` Tom Lendacky
2016-06-17 15:51 ` Matt Fleming
2016-04-26 22:57 ` [RFC PATCH v1 11/18] x86: Decrypt trampoline area if memory encryption is active Tom Lendacky
2016-04-26 22:58 ` [RFC PATCH v1 12/18] x86: Access device tree in the clear Tom Lendacky
2016-04-26 22:58 ` [RFC PATCH v1 13/18] x86: DMA support for memory encryption Tom Lendacky
[not found] ` <20160429071743.GC11592@char.us.oracle.com>
2016-04-29 15:12 ` Tom Lendacky
[not found] ` <20160429162757.GA1191@char.us.oracle.com>
2016-04-29 23:49 ` Tom Lendacky
2016-04-26 22:58 ` [RFC PATCH v1 14/18] iommu/amd: AMD IOMMU " Tom Lendacky
2016-04-26 22:58 ` [RFC PATCH v1 15/18] x86: Enable memory encryption on the APs Tom Lendacky
2016-05-01 22:10 ` Huang, Kai
2016-05-03 15:59 ` Tom Lendacky
2016-04-26 22:58 ` [RFC PATCH v1 16/18] x86: Do not specify encrypted memory for VGA mapping Tom Lendacky
2016-04-26 22:58 ` [RFC PATCH v1 17/18] x86/kvm: Enable Secure Memory Encryption of nested page tables Tom Lendacky
2016-04-26 22:59 ` [RFC PATCH v1 18/18] x86: Add support to turn on Secure Memory Encryption Tom Lendacky
2016-03-22 13:13 ` Pavel Machek
2016-04-27 14:39 ` [RFC PATCH v1 00/18] x86: Secure Memory Encryption (AMD) Andy Lutomirski
2016-04-27 20:10 ` Tom Lendacky
2016-05-02 18:31 ` Andy Lutomirski
2016-05-09 15:13 ` Paolo Bonzini
2016-05-09 21:08 ` Tom Lendacky
2016-05-10 11:23 ` Paolo Bonzini
2016-05-10 12:04 ` Borislav Petkov
2016-04-30 6:13 ` Elliott, Robert (Persistent Memory)
2016-05-03 15:55 ` Tom Lendacky
-- strict thread matches above, loose matches on Subject: below --
2016-04-26 22:45 Tom Lendacky
2016-04-26 22:47 ` [RFC PATCH v1 10/18] x86/efi: Access EFI related tables in the clear Tom Lendacky
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