From: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>
To: Tom Lendacky <thomas.lendacky-5C7GfCeVMHo@public.gmane.org>
Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
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"Radim Krčmář" <rkrcmar-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Matt Fleming"
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x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
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"Michael S. Tsirkin"
<mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Paolo Bonzini"
<pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC PATCH v4 01/28] x86: Documentation for AMD Secure Memory Encryption (SME)
Date: Thu, 16 Feb 2017 18:56:25 +0100 [thread overview]
Message-ID: <20170216175625.imxsvz7fzvlpveze@pd.tnic> (raw)
In-Reply-To: <20170216154211.19244.76656.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
Ok, this time detailed review :-)
On Thu, Feb 16, 2017 at 09:42:11AM -0600, Tom Lendacky wrote:
> This patch adds a Documenation entry to decribe the AMD Secure Memory
> Encryption (SME) feature.
Please introduce a spellchecker into your patch creation workflow. I see
two typos in one line.
Also, never start patch commit messages with "This patch" - we know it
is this patch. Always write a doer-sentences explaining the why, not the
what. Something like:
"Add a SME and mem_encrypt= kernel parameter documentation."
for example.
> Signed-off-by: Tom Lendacky <thomas.lendacky-5C7GfCeVMHo@public.gmane.org>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 11 ++++
> Documentation/x86/amd-memory-encryption.txt | 57 +++++++++++++++++++++++
> 2 files changed, 68 insertions(+)
> create mode 100644 Documentation/x86/amd-memory-encryption.txt
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 110745e..91c40fa 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2145,6 +2145,17 @@
> memory contents and reserves bad memory
> regions that are detected.
>
> + mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
> + Valid arguments: on, off
> + Default (depends on kernel configuration option):
> + on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
> + off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
> + mem_encrypt=on: Activate SME
> + mem_encrypt=off: Do not activate SME
> +
> + Refer to the SME documentation for details on when
"Refer to Documentation/x86/amd-memory-encryption.txt .."
> + memory encryption can be activated.
> +
> mem_sleep_default= [SUSPEND] Default system suspend mode:
> s2idle - Suspend-To-Idle
> shallow - Power-On Suspend or equivalent (if supported)
> diff --git a/Documentation/x86/amd-memory-encryption.txt b/Documentation/x86/amd-memory-encryption.txt
> new file mode 100644
> index 0000000..0938e89
> --- /dev/null
> +++ b/Documentation/x86/amd-memory-encryption.txt
> @@ -0,0 +1,57 @@
> +Secure Memory Encryption (SME) is a feature found on AMD processors.
> +
> +SME provides the ability to mark individual pages of memory as encrypted using
> +the standard x86 page tables. A page that is marked encrypted will be
> +automatically decrypted when read from DRAM and encrypted when written to
> +DRAM. SME can therefore be used to protect the contents of DRAM from physical
> +attacks on the system.
> +
> +A page is encrypted when a page table entry has the encryption bit set (see
> +below how to determine the position of the bit). The encryption bit can be
"... how to determine its position)."
> +specified in the cr3 register, allowing the PGD table to be encrypted. Each
> +successive level of page tables can also be encrypted.
> +
> +Support for SME can be determined through the CPUID instruction. The CPUID
> +function 0x8000001f reports information related to SME:
> +
> + 0x8000001f[eax]:
> + Bit[0] indicates support for SME
> + 0x8000001f[ebx]:
> + Bit[5:0] pagetable bit number used to activate memory
> + encryption
s/Bit/Bits/
> + Bit[11:6] reduction in physical address space, in bits, when
Ditto.
> + memory encryption is enabled (this only affects system
> + physical addresses, not guest physical addresses)
> +
> +If support for SME is present, MSR 0xc00100010 (SYS_CFG) can be used to
Let's use the kernel's define name MSR_K8_SYSCFG to avoid ambiguity.
> +determine if SME is enabled and/or to enable memory encryption:
> +
> + 0xc0010010:
> + Bit[23] 0 = memory encryption features are disabled
> + 1 = memory encryption features are enabled
> +
> +Linux relies on BIOS to set this bit if BIOS has determined that the reduction
> +in the physical address space as a result of enabling memory encryption (see
> +CPUID information above) will not conflict with the address space resource
> +requirements for the system. If this bit is not set upon Linux startup then
> +Linux itself will not set it and memory encryption will not be possible.
> +
> +The state of SME in the Linux kernel can be documented as follows:
> + - Supported:
> + The CPU supports SME (determined through CPUID instruction).
> +
> + - Enabled:
> + Supported and bit 23 of the SYS_CFG MSR is set.
Ditto.
> +
> + - Active:
> + Supported, Enabled and the Linux kernel is actively applying
> + the encryption bit to page table entries (the SME mask in the
> + kernel is non-zero).
> +
> +SME can also be enabled and activated in the BIOS. If SME is enabled and
> +activated in the BIOS, then all memory accesses will be encrypted and it will
> +not be necessary to activate the Linux memory encryption support. If the BIOS
> +merely enables SME (sets bit 23 of the SYS_CFG MSR), then Linux can activate
> +memory encryption.
"... This is done by supplying mem_encrypt=on on the kernel command line.
Alternatively, if the kernel should enable SME by default, set
CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y."
> However, if BIOS does not enable SME, then Linux will not
> +attempt to activate memory encryption, even if configured to do so by default
will not attempt or will not be able to?
> +or the mem_encrypt=on command line parameter is specified.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2017-02-16 17:56 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-16 15:41 [RFC PATCH v4 00/28] x86: Secure Memory Encryption (AMD) Tom Lendacky
2017-02-16 15:42 ` [RFC PATCH v4 01/28] x86: Documentation for AMD Secure Memory Encryption (SME) Tom Lendacky
[not found] ` <20170216154211.19244.76656.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-16 17:56 ` Borislav Petkov [this message]
2017-02-16 19:48 ` Tom Lendacky
2017-02-16 15:42 ` [RFC PATCH v4 02/28] x86: Set the write-protect cache mode for full PAT support Tom Lendacky
[not found] ` <20170216154225.19244.96438.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-17 11:07 ` Borislav Petkov
2017-02-17 15:56 ` Tom Lendacky
2017-02-16 15:42 ` [RFC PATCH v4 03/28] x86: Add the Secure Memory Encryption CPU feature Tom Lendacky
[not found] ` <20170216154236.19244.7580.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-16 18:13 ` Borislav Petkov
2017-02-16 19:42 ` Tom Lendacky
[not found] ` <a1a6a6d7-3aac-3138-1e75-6160f0427a6b-5C7GfCeVMHo@public.gmane.org>
2017-02-16 20:06 ` Borislav Petkov
2017-02-16 15:42 ` [RFC PATCH v4 04/28] x86: Handle reduction in physical address size with SME Tom Lendacky
2017-02-17 11:04 ` Borislav Petkov
2017-02-16 15:43 ` [RFC PATCH v4 05/28] x86: Add Secure Memory Encryption (SME) support Tom Lendacky
2017-02-17 12:00 ` Borislav Petkov
2017-02-25 15:29 ` Borislav Petkov
2017-02-28 23:01 ` Tom Lendacky
2017-02-16 15:43 ` [RFC PATCH v4 06/28] x86: Add support to enable SME during early boot processing Tom Lendacky
[not found] ` <20170216154319.19244.7863.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-20 12:51 ` Borislav Petkov
2017-02-21 14:55 ` Tom Lendacky
[not found] ` <a23be4fa-d7ef-4e7a-5b6b-73e120a5ca80-5C7GfCeVMHo@public.gmane.org>
2017-02-21 15:10 ` Borislav Petkov
2017-02-16 15:43 ` [RFC PATCH v4 07/28] x86: Provide general kernel support for memory encryption Tom Lendacky
[not found] ` <20170216154332.19244.55451.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-20 15:21 ` Borislav Petkov
2017-02-21 17:18 ` Tom Lendacky
2017-02-22 12:08 ` Borislav Petkov
2017-02-20 18:38 ` Borislav Petkov
2017-02-22 16:43 ` Tom Lendacky
2017-02-22 18:13 ` Dave Hansen
2017-02-23 23:12 ` Tom Lendacky
2017-02-22 18:13 ` Dave Hansen
2017-02-16 15:43 ` [RFC PATCH v4 08/28] x86: Extend the early_memremap support with additional attrs Tom Lendacky
[not found] ` <20170216154348.19244.11884.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-20 15:43 ` Borislav Petkov
2017-02-22 15:42 ` Tom Lendacky
2017-02-16 15:43 ` [RFC PATCH v4 09/28] x86: Add support for early encryption/decryption of memory Tom Lendacky
[not found] ` <20170216154358.19244.6082.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-20 18:22 ` Borislav Petkov
2017-02-22 15:48 ` Tom Lendacky
2017-02-16 15:44 ` [RFC PATCH v4 10/28] x86: Insure that boot memory areas are mapped properly Tom Lendacky
[not found] ` <20170216154411.19244.99258.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-20 19:45 ` Borislav Petkov
2017-02-22 18:34 ` Tom Lendacky
2017-02-16 15:44 ` [RFC PATCH v4 11/28] x86: Add support to determine the E820 type of an address Tom Lendacky
[not found] ` <20170216154430.19244.95519.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-20 20:09 ` Borislav Petkov
2017-02-28 22:34 ` Tom Lendacky
2017-03-03 9:52 ` Borislav Petkov
2017-02-16 15:44 ` [RFC PATCH v4 12/28] efi: Add an EFI table address match function Tom Lendacky
2017-02-16 15:44 ` [RFC PATCH v4 13/28] efi: Update efi_mem_type() to return defined EFI mem types Tom Lendacky
2017-02-21 12:05 ` Matt Fleming
2017-02-23 17:27 ` Tom Lendacky
2017-02-24 9:57 ` Matt Fleming
2017-02-16 15:45 ` [RFC PATCH v4 14/28] Add support to access boot related data in the clear Tom Lendacky
[not found] ` <20170216154508.19244.58580.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-21 15:06 ` Borislav Petkov
2017-02-23 21:34 ` Tom Lendacky
2017-02-24 10:21 ` Borislav Petkov
2017-02-24 15:04 ` Tom Lendacky
2017-02-24 15:22 ` Borislav Petkov
2017-03-08 6:55 ` Dave Young
2017-03-17 19:50 ` Tom Lendacky
2017-02-16 15:45 ` [RFC PATCH v4 15/28] Add support to access persistent memory " Tom Lendacky
2017-03-17 22:58 ` Elliott, Robert (Persistent Memory)
2017-03-23 21:02 ` Tom Lendacky
2017-02-16 15:45 ` [RFC PATCH v4 16/28] x86: Add support for changing memory encryption attribute Tom Lendacky
2017-02-22 18:52 ` Borislav Petkov
2017-02-28 22:46 ` Tom Lendacky
2017-02-16 15:45 ` [RFC PATCH v4 17/28] x86: Decrypt trampoline area if memory encryption is active Tom Lendacky
2017-02-16 15:46 ` [RFC PATCH v4 18/28] x86: DMA support for memory encryption Tom Lendacky
2017-02-25 17:10 ` Borislav Petkov
2017-03-06 17:47 ` Tom Lendacky
2017-02-16 15:46 ` [RFC PATCH v4 19/28] swiotlb: Add warnings for use of bounce buffers with SME Tom Lendacky
2017-02-17 15:59 ` Konrad Rzeszutek Wilk
2017-02-17 16:51 ` Tom Lendacky
2017-03-02 17:01 ` Paolo Bonzini
2017-02-27 17:52 ` Borislav Petkov
2017-02-28 23:19 ` Tom Lendacky
2017-03-01 11:17 ` Borislav Petkov
2017-02-16 15:46 ` [RFC PATCH v4 20/28] iommu/amd: Disable AMD IOMMU if memory encryption is active Tom Lendacky
2017-02-16 15:46 ` [RFC PATCH v4 21/28] x86: Check for memory encryption on the APs Tom Lendacky
[not found] ` <20170216154647.19244.18733.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-27 18:17 ` Borislav Petkov
2017-02-28 23:28 ` Tom Lendacky
[not found] ` <5f461d57-9232-1cb3-d4d9-9b8a39d00b12-5C7GfCeVMHo@public.gmane.org>
2017-03-01 11:17 ` Borislav Petkov
2017-02-16 15:47 ` [RFC PATCH v4 22/28] x86: Do not specify encrypted memory for video mappings Tom Lendacky
2017-02-16 15:47 ` [RFC PATCH v4 23/28] x86/kvm: Enable Secure Memory Encryption of nested page tables Tom Lendacky
2017-02-16 15:47 ` [RFC PATCH v4 24/28] x86: Access the setup data through debugfs decrypted Tom Lendacky
2017-03-08 7:04 ` Dave Young
2017-03-17 19:54 ` Tom Lendacky
2017-02-16 15:47 ` [RFC PATCH v4 25/28] x86: Access the setup data through sysfs decrypted Tom Lendacky
2017-03-08 7:09 ` Dave Young
2017-03-17 20:09 ` Tom Lendacky
2017-02-16 15:47 ` [RFC PATCH v4 26/28] x86: Allow kexec to be used with SME Tom Lendacky
2017-02-17 15:57 ` Konrad Rzeszutek Wilk
2017-02-17 16:43 ` Tom Lendacky
2017-03-01 9:25 ` Dave Young
2017-03-01 9:27 ` Dave Young
2017-03-06 17:58 ` Tom Lendacky
2017-03-06 18:04 ` Tom Lendacky
2017-03-08 8:12 ` Dave Young
2017-02-28 10:35 ` Borislav Petkov
2017-03-01 15:36 ` Tom Lendacky
2017-02-16 15:48 ` [RFC PATCH v4 27/28] x86: Add support to encrypt the kernel in-place Tom Lendacky
[not found] ` <20170216154808.19244.475.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-03-01 17:36 ` Borislav Petkov
2017-03-02 18:30 ` Tom Lendacky
2017-03-02 18:51 ` Borislav Petkov
2017-02-16 15:48 ` [RFC PATCH v4 28/28] x86: Add support to make use of Secure Memory Encryption Tom Lendacky
2017-03-01 18:40 ` Borislav Petkov
2017-03-07 16:05 ` Tom Lendacky
2017-03-07 17:42 ` Borislav Petkov
2017-03-08 15:05 ` Borislav Petkov
[not found] ` <20170216154158.19244.66630.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org>
2017-02-18 18:12 ` [RFC PATCH v4 00/28] x86: Secure Memory Encryption (AMD) Borislav Petkov
2017-02-21 15:09 ` Tom Lendacky
2017-02-21 17:42 ` Rik van Riel
[not found] ` <1487698965.17158.8.camel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-02-21 17:53 ` Borislav Petkov
2017-03-01 9:17 ` Dave Young
2017-03-01 17:51 ` Tom Lendacky
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