From: Boris Petkov <bp@alien8.de>
To: Dave Hansen <dave.hansen@intel.com>,
Dan Williams <dan.j.williams@intel.com>
Cc: Martin Fernandez <martin.fernandez@eclypsium.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-efi <linux-efi@vger.kernel.org>,
platform-driver-x86@vger.kernel.org,
Linux MM <linux-mm@kvack.org>, "H. Peter Anvin" <hpa@zytor.com>,
daniel.gutson@eclypsium.com, Darren Hart <dvhart@infradead.org>,
Andy Shevchenko <andy@infradead.org>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Ard Biesheuvel <ardb@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>, X86 ML <x86@kernel.org>,
"Schofield, Alison" <alison.schofield@intel.com>,
hughsient@gmail.com, alex.bazhaniuk@eclypsium.com,
Greg KH <gregkh@linuxfoundation.org>,
Mike Rapoport <rppt@kernel.org>,
Ben Widawsky <ben.widawsky@intel.com>,
"Huang, Kai" <kai.huang@intel.com>
Subject: Re: [PATCH v8 0/8] x86: Show in sysfs if a memory node is able to do encryption
Date: Fri, 06 May 2022 19:02:03 +0000 [thread overview]
Message-ID: <CE52D65A-C9F4-408D-B18A-72D87495A433@alien8.de> (raw)
In-Reply-To: <4bc56567-e2ce-40ec-19ab-349c8de8d969@intel.com>
On May 6, 2022 6:43:39 PM UTC, Dave Hansen <dave.hansen@intel.com> wrote:
>On 5/6/22 11:25, Boris Petkov wrote:
>> On May 6, 2022 6:14:00 PM UTC, Dave Hansen <dave.hansen@intel.com>
>> wrote:
>>> But, this interface will *work* both for the uniform and
>>> non-uniform systems alike.
>> And what would that additional information that some "node" -
>> whatever "node" means nowadays - is not encrypted give you?
>
>Tying it to the node ties it to the NUMA ABIs. For instance, it lets
>you say: "allocate memory with encryption capabilities" with a
>set_mempolicy() to nodes that are enumerated as encryption-capable.
I was expecting something along those lines...
>Imagine that we have a non-uniform system: some memory supports TDX (or
>SEV-SNP) and some doesn't. QEMU calls mmap() to allocate some guest
>memory and then its ioctl()s to get its addresses stuffed into EPT/NPT.
> The memory might be allocated from anywhere, CPU_CRYPTO-capable or not.
> VM creation will fail because the (hardware-enforced) security checks
>can't be satisfied on non-CPU_CRYPTO memory.
>
>Userspace has no recourse to fix this. It's just stuck. In that case,
> the *kernel* needs to be responsible for ensuring that the backing
>physical memory supports TDX (or SEV).
>
>This node attribute punts the problem back out to userspace. It gives
>userspace the ability to steer allocations to compatible NUMA nodes. If
>something goes wrong, they can use other NUMA ABIs to inspect the
>situation, like /proc/$pid/numa_maps.
That's all fine and dandy but I still don't see the *actual*, real-life use case of why something would request memory of particular encryption capabilities. Don't get me wrong - I'm not saying there are not such use cases - I'm saying we should go all the way and fully define properly *why* we're doing this whole hoopla.
Remember - this all started with "i wanna say that mem enc is active" and now we're so far deep down the rabbit hole...
--
Sent from a small device: formatting sux and brevity is inevitable.
next prev parent reply other threads:[~2022-05-06 19:02 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-29 20:17 [PATCH v8 0/8] x86: Show in sysfs if a memory node is able to do encryption Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 1/8] mm/memblock: Tag memblocks with crypto capabilities Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 2/8] mm/mmzone: Tag pg_data_t " Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 3/8] x86/e820: Add infrastructure to refactor e820__range_{update,remove} Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 4/8] x86/e820: Refactor __e820__range_update Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 5/8] x86/e820: Refactor e820__range_remove Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 6/8] x86/e820: Tag e820_entry with crypto capabilities Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 7/8] x86/efi: Mark e820_entries as crypto capable from EFI memmap Martin Fernandez
2022-04-29 20:17 ` [PATCH v8 8/8] drivers/node: Show in sysfs node's crypto capabilities Martin Fernandez
2022-05-04 16:38 ` [PATCH v8 0/8] x86: Show in sysfs if a memory node is able to do encryption Borislav Petkov
2022-05-04 17:18 ` Martin Fernandez
2022-05-06 12:44 ` Borislav Petkov
2022-05-06 14:18 ` Limonciello, Mario
2022-05-06 15:32 ` Dave Hansen
2022-05-06 16:00 ` Dan Williams
2022-05-06 17:55 ` Boris Petkov
2022-05-06 18:14 ` Dave Hansen
2022-05-06 18:25 ` Boris Petkov
2022-05-06 18:43 ` Dave Hansen
2022-05-06 19:02 ` Boris Petkov [this message]
2022-05-09 18:47 ` Dave Hansen
2022-05-09 22:17 ` Borislav Petkov
2022-05-09 22:56 ` Dave Hansen
2022-05-16 8:39 ` Richard Hughes
2022-05-18 7:52 ` Borislav Petkov
2022-05-18 18:28 ` Dan Williams
2022-05-18 20:23 ` Borislav Petkov
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