From: "Michael S. Tsirkin" <mst@redhat.com> To: Borislav Petkov <bp@alien8.de> Cc: "Tom Lendacky" <thomas.lendacky@amd.com>, 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, "Rik van Riel" <riel@redhat.com>, "Radim Krčmář" <rkrcmar@redhat.com>, "Arnd Bergmann" <arnd@arndb.de>, "Jonathan Corbet" <corbet@lwn.net>, "Matt Fleming" <matt@codeblueprint.co.uk>, "Joerg Roedel" <joro@8bytes.org>, "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>, "Paolo Bonzini" <pbonzini@redhat.com>, "Larry Woodman" <lwoodman@redhat.com>, "Ingo Molnar" <mingo@redhat.com>, "Andy Lutomirski" <luto@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, "Andrey Ryabinin" <aryabinin@virtuozzo.com> Subject: Re: [RFC PATCH v3 13/20] x86: DMA support for memory encryption Date: Tue, 22 Nov 2016 17:22:38 +0200 [thread overview] Message-ID: <20161122171455-mutt-send-email-mst@kernel.org> (raw) In-Reply-To: <20161122113859.5dtlrfgizwpum6st@pd.tnic> On Tue, Nov 22, 2016 at 12:38:59PM +0100, Borislav Petkov wrote: > On Tue, Nov 15, 2016 at 12:29:35PM -0600, Tom Lendacky wrote: > > > Makes sense, but I think at least a dmesg warning here > > > might be a good idea. > > > > Good idea. Should it be a warning when it is first being set up or > > a warning the first time the bounce buffers need to be used. Or maybe > > both? > > Ok, let me put my user hat on... > > (... puts a felt hat ...) > > so what am I supposed to do about this as a user? Go and physically > remove those devices because I want to enable SME?! > > IMO, the only thing we should do is issue a *single* warning - > pr_warn_once - along the lines of: > > "... devices present which due to SME will use bounce buffers and will > cause their speed to diminish. Boot with sme=debug to see full info". > > And then sme=debug will dump the whole gory details. I don't think > screaming for each device is going to change anything in many cases. > 99% of people don't care - they just want shit to work. The issue is it's a (potential) security hole, not a slowdown. > > > A boot flag that says "don't enable devices that don't support > > > encryption" might be a good idea, too, since most people > > > don't read dmesg output and won't notice the message. > > > > I'll look into this. It might be something that can be checked as > > part of the device setting its DMA mask or the first time a DMA > > API is used if the device doesn't explicitly set its mask. > > Still with my user hat on, what would be the purpose of such an option? > > We already use bounce buffers so those devices do support encryption, > albeit slower. > > felt hat is confused. To disable unsecure things. If someone enables SEV one might have an expectation of security. Might help push vendors to do the right thing as a side effect. > -- > Regards/Gruss, > Boris. > > Good mailing practices for 400: avoid top-posting and trim the reply. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com> To: Borislav Petkov <bp@alien8.de> Cc: "Tom Lendacky" <thomas.lendacky@amd.com>, 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, "Rik van Riel" <riel@redhat.com>, "Radim Krčmář" <rkrcmar@redhat.com>, "Arnd Bergmann" <arnd@arndb.de>, "Jonathan Corbet" <corbet@lwn.net>, "Matt Fleming" <matt@codeblueprint.co.uk>, "Joerg Roedel" <joro@8bytes.org>, "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>, "Paolo Bonzini" <pbonzini@redhat.com>, "Larry Woodman" <lwoodman@redhat.com>, "Ingo Molnar" <mingo@redhat.com>, "Andy Lutomirski" <luto@kernel.org>, "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 v3 13/20] x86: DMA support for memory encryption Date: Tue, 22 Nov 2016 17:22:38 +0200 [thread overview] Message-ID: <20161122171455-mutt-send-email-mst@kernel.org> (raw) Message-ID: <20161122152238.bra1uNZ5SE4xtOxebtXLoWruZkcICzqbd7PGrztZ9DI@z> (raw) In-Reply-To: <20161122113859.5dtlrfgizwpum6st@pd.tnic> On Tue, Nov 22, 2016 at 12:38:59PM +0100, Borislav Petkov wrote: > On Tue, Nov 15, 2016 at 12:29:35PM -0600, Tom Lendacky wrote: > > > Makes sense, but I think at least a dmesg warning here > > > might be a good idea. > > > > Good idea. Should it be a warning when it is first being set up or > > a warning the first time the bounce buffers need to be used. Or maybe > > both? > > Ok, let me put my user hat on... > > (... puts a felt hat ...) > > so what am I supposed to do about this as a user? Go and physically > remove those devices because I want to enable SME?! > > IMO, the only thing we should do is issue a *single* warning - > pr_warn_once - along the lines of: > > "... devices present which due to SME will use bounce buffers and will > cause their speed to diminish. Boot with sme=debug to see full info". > > And then sme=debug will dump the whole gory details. I don't think > screaming for each device is going to change anything in many cases. > 99% of people don't care - they just want shit to work. The issue is it's a (potential) security hole, not a slowdown. > > > A boot flag that says "don't enable devices that don't support > > > encryption" might be a good idea, too, since most people > > > don't read dmesg output and won't notice the message. > > > > I'll look into this. It might be something that can be checked as > > part of the device setting its DMA mask or the first time a DMA > > API is used if the device doesn't explicitly set its mask. > > Still with my user hat on, what would be the purpose of such an option? > > We already use bounce buffers so those devices do support encryption, > albeit slower. > > felt hat is confused. To disable unsecure things. If someone enables SEV one might have an expectation of security. Might help push vendors to do the right thing as a side effect. > -- > Regards/Gruss, > Boris. > > Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2016-11-22 15:22 UTC|newest] Thread overview: 156+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-11-10 0:34 [RFC PATCH v3 00/20] x86: Secure Memory Encryption (AMD) Tom Lendacky 2016-11-10 0:34 ` Tom Lendacky 2016-11-10 0:34 ` [RFC PATCH v3 01/20] x86: Documentation for AMD Secure Memory Encryption (SME) Tom Lendacky 2016-11-10 0:34 ` Tom Lendacky 2016-11-10 10:51 ` Borislav Petkov 2016-11-10 10:51 ` Borislav Petkov 2016-11-14 17:15 ` Tom Lendacky 2016-11-14 17:15 ` Tom Lendacky 2016-11-10 0:34 ` [RFC PATCH v3 02/20] x86: Set the write-protect cache mode for full PAT support Tom Lendacky 2016-11-10 0:34 ` Tom Lendacky 2016-11-10 13:14 ` Borislav Petkov 2016-11-10 13:14 ` Borislav Petkov 2016-11-11 1:26 ` Kani, Toshimitsu 2016-11-11 1:26 ` Kani, Toshimitsu [not found] ` <1478827480.20881.142.camel-ZPxbGqLxI0U@public.gmane.org> 2016-11-14 16:51 ` Tom Lendacky 2016-11-14 16:51 ` Tom Lendacky 2016-11-10 0:35 ` [RFC PATCH v3 07/20] x86: Provide general kernel support for memory encryption Tom Lendacky 2016-11-10 0:35 ` Tom Lendacky 2016-11-10 0:36 ` [RFC PATCH v3 08/20] x86: Add support for early encryption/decryption of memory Tom Lendacky 2016-11-10 0:36 ` Tom Lendacky [not found] ` <20161110003610.3280.22043.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-16 10:46 ` Borislav Petkov 2016-11-16 10:46 ` Borislav Petkov [not found] ` <20161116104656.qz5wp33zzyja373r-fF5Pk5pvG8Y@public.gmane.org> 2016-11-16 19:22 ` Tom Lendacky 2016-11-16 19:22 ` Tom Lendacky 2016-11-10 0:36 ` [RFC PATCH v3 09/20] x86: Insure that boot memory areas are mapped properly Tom Lendacky 2016-11-10 0:36 ` Tom Lendacky [not found] ` <20161110003620.3280.20613.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-17 12:20 ` Borislav Petkov 2016-11-17 12:20 ` Borislav Petkov 2016-11-19 18:12 ` Tom Lendacky 2016-11-19 18:12 ` Tom Lendacky 2016-11-10 0:37 ` [RFC PATCH v3 13/20] x86: DMA support for memory encryption Tom Lendacky 2016-11-10 0:37 ` Tom Lendacky 2016-11-15 14:39 ` Radim Krčmář 2016-11-15 14:39 ` Radim Krčmář 2016-11-15 17:02 ` Tom Lendacky 2016-11-15 17:02 ` Tom Lendacky [not found] ` <d5ebd13d-1278-8714-3f03-8ee7f04a2b38-5C7GfCeVMHo@public.gmane.org> 2016-11-15 18:17 ` Radim Krčmář 2016-11-15 18:17 ` Radim Krčmář 2016-11-15 20:33 ` Tom Lendacky 2016-11-15 20:33 ` Tom Lendacky 2016-11-15 15:16 ` Michael S. Tsirkin 2016-11-15 15:16 ` Michael S. Tsirkin [not found] ` <20161115171443-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> 2016-11-15 18:29 ` Tom Lendacky 2016-11-15 18:29 ` Tom Lendacky 2016-11-15 19:16 ` Michael S. Tsirkin 2016-11-15 19:16 ` Michael S. Tsirkin 2016-11-22 11:38 ` Borislav Petkov 2016-11-22 11:38 ` Borislav Petkov 2016-11-22 15:22 ` Michael S. Tsirkin [this message] 2016-11-22 15:22 ` Michael S. Tsirkin 2016-11-22 15:41 ` Borislav Petkov 2016-11-22 15:41 ` Borislav Petkov [not found] ` <20161122154137.z5vp3xcl5cpesuiz-fF5Pk5pvG8Y@public.gmane.org> 2016-11-22 20:41 ` Michael S. Tsirkin 2016-11-22 20:41 ` Michael S. Tsirkin 2016-11-10 0:37 ` [RFC PATCH v3 15/20] x86: Check for memory encryption on the APs Tom Lendacky 2016-11-10 0:37 ` Tom Lendacky 2016-11-22 19:25 ` Borislav Petkov 2016-11-22 19:25 ` Borislav Petkov [not found] ` <20161122192526.vg63jjhwsbjwex7i-fF5Pk5pvG8Y@public.gmane.org> 2016-11-29 18:00 ` Tom Lendacky 2016-11-29 18:00 ` Tom Lendacky [not found] ` <20161110003426.3280.2999.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-10 0:34 ` [RFC PATCH v3 03/20] x86: Add the Secure Memory Encryption cpu feature Tom Lendacky 2016-11-10 0:34 ` Tom Lendacky 2016-11-11 11:53 ` Borislav Petkov 2016-11-11 11:53 ` Borislav Petkov 2016-11-10 0:35 ` [RFC PATCH v3 04/20] x86: Handle reduction in physical address size with SME Tom Lendacky 2016-11-10 0:35 ` Tom Lendacky [not found] ` <20161110003513.3280.12104.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-15 12:10 ` Joerg Roedel 2016-11-15 12:10 ` Joerg Roedel 2016-11-15 12:14 ` Borislav Petkov 2016-11-15 12:14 ` Borislav Petkov 2016-11-15 14:40 ` Tom Lendacky 2016-11-15 14:40 ` Tom Lendacky [not found] ` <a4cc5b07-89e1-aaa0-1977-1de95883ba62-5C7GfCeVMHo@public.gmane.org> 2016-11-15 15:33 ` Borislav Petkov 2016-11-15 15:33 ` Borislav Petkov [not found] ` <20161115153338.a2cxmatnpqcgiaiy-fF5Pk5pvG8Y@public.gmane.org> 2016-11-15 16:06 ` Tom Lendacky 2016-11-15 16:06 ` Tom Lendacky 2016-11-15 16:33 ` Borislav Petkov 2016-11-15 16:33 ` Borislav Petkov 2016-11-15 17:08 ` Tom Lendacky 2016-11-15 17:08 ` Tom Lendacky [not found] ` <20161115121456.f4slpk4i2jl3e2ke-fF5Pk5pvG8Y@public.gmane.org> 2016-11-15 21:22 ` Tom Lendacky 2016-11-15 21:22 ` Tom Lendacky 2016-11-15 21:33 ` Borislav Petkov 2016-11-15 21:33 ` Borislav Petkov 2016-11-15 22:01 ` Tom Lendacky 2016-11-15 22:01 ` Tom Lendacky [not found] ` <20161115121035.GD24857-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> 2016-11-15 14:32 ` Tom Lendacky 2016-11-15 14:32 ` Tom Lendacky 2016-11-10 0:35 ` [RFC PATCH v3 05/20] x86: Add Secure Memory Encryption (SME) support Tom Lendacky 2016-11-10 0:35 ` Tom Lendacky 2016-11-10 0:35 ` [RFC PATCH v3 06/20] x86: Add support to enable SME during early boot processing Tom Lendacky 2016-11-10 0:35 ` Tom Lendacky [not found] ` <20161110003543.3280.99623.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-14 17:29 ` Borislav Petkov 2016-11-14 17:29 ` Borislav Petkov 2016-11-14 18:18 ` Tom Lendacky 2016-11-14 18:18 ` Tom Lendacky 2016-11-14 20:01 ` Borislav Petkov 2016-11-14 20:01 ` Borislav Petkov 2016-11-10 0:36 ` [RFC PATCH v3 10/20] Add support to access boot related data in the clear Tom Lendacky 2016-11-10 0:36 ` Tom Lendacky 2016-11-11 16:17 ` Kani, Toshimitsu 2016-11-11 16:17 ` Kani, Toshimitsu [not found] ` <1478880929.20881.148.camel-ZPxbGqLxI0U@public.gmane.org> 2016-11-14 16:24 ` Tom Lendacky 2016-11-14 16:24 ` Tom Lendacky 2016-11-17 15:55 ` Borislav Petkov 2016-11-17 15:55 ` Borislav Petkov [not found] ` <20161117155543.vg3domfqm3bhp4f7-fF5Pk5pvG8Y@public.gmane.org> 2016-11-19 18:33 ` Tom Lendacky 2016-11-19 18:33 ` Tom Lendacky 2016-11-20 23:04 ` Borislav Petkov 2016-11-20 23:04 ` Borislav Petkov [not found] ` <20161110003631.3280.73292.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-12-07 13:19 ` Matt Fleming 2016-12-07 13:19 ` Matt Fleming 2016-12-09 14:26 ` Tom Lendacky 2016-12-09 14:26 ` Tom Lendacky 2016-11-10 0:36 ` [RFC PATCH v3 11/20] x86: Add support for changing memory encryption attribute Tom Lendacky 2016-11-10 0:36 ` Tom Lendacky [not found] ` <20161110003655.3280.57333.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-17 17:39 ` Borislav Petkov 2016-11-17 17:39 ` Borislav Petkov 2016-11-19 18:48 ` Tom Lendacky 2016-11-19 18:48 ` Tom Lendacky [not found] ` <6f1a16e4-5a84-20c0-4bd3-3be5ed933800-5C7GfCeVMHo@public.gmane.org> 2016-11-21 8:27 ` Borislav Petkov 2016-11-21 8:27 ` Borislav Petkov 2016-11-10 0:37 ` [RFC PATCH v3 12/20] x86: Decrypt trampoline area if memory encryption is active Tom Lendacky 2016-11-10 0:37 ` Tom Lendacky [not found] ` <20161110003708.3280.29934.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-17 18:09 ` Borislav Petkov 2016-11-17 18:09 ` Borislav Petkov 2016-11-19 18:50 ` Tom Lendacky 2016-11-19 18:50 ` Tom Lendacky 2016-11-10 0:37 ` [RFC PATCH v3 14/20] iommu/amd: Disable AMD IOMMU " Tom Lendacky 2016-11-10 0:37 ` Tom Lendacky 2016-11-14 16:32 ` Joerg Roedel 2016-11-14 16:32 ` Joerg Roedel 2016-11-14 16:48 ` Tom Lendacky 2016-11-14 16:48 ` Tom Lendacky 2016-11-10 0:37 ` [RFC PATCH v3 16/20] x86: Do not specify encrypted memory for video mappings Tom Lendacky 2016-11-10 0:37 ` Tom Lendacky 2016-11-10 0:38 ` [RFC PATCH v3 17/20] x86/kvm: Enable Secure Memory Encryption of nested page tables Tom Lendacky 2016-11-10 0:38 ` Tom Lendacky 2016-11-10 0:38 ` [RFC PATCH v3 18/20] x86: Access the setup data through debugfs un-encrypted Tom Lendacky 2016-11-10 0:38 ` Tom Lendacky 2016-11-10 0:38 ` [RFC PATCH v3 19/20] x86: Add support to make use of Secure Memory Encryption Tom Lendacky 2016-11-10 0:38 ` Tom Lendacky [not found] ` <20161110003826.3280.5546.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-24 12:50 ` Borislav Petkov 2016-11-24 12:50 ` Borislav Petkov 2016-11-29 18:40 ` Tom Lendacky 2016-11-29 18:40 ` Tom Lendacky 2016-11-10 0:38 ` [RFC PATCH v3 20/20] " Tom Lendacky 2016-11-10 0:38 ` Tom Lendacky [not found] ` <20161110003838.3280.23327.stgit-qCXWGYdRb2BnqfbPTmsdiZQ+2ll4COg0XqFh9Ls21Oc@public.gmane.org> 2016-11-22 18:58 ` Borislav Petkov 2016-11-22 18:58 ` Borislav Petkov 2016-11-26 20:47 ` Borislav Petkov 2016-11-26 20:47 ` Borislav Petkov 2016-11-29 18:48 ` Tom Lendacky 2016-11-29 18:48 ` Tom Lendacky 2016-11-29 19:56 ` Borislav Petkov 2016-11-29 19:56 ` Borislav Petkov
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