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From: Mike Rapoport <rppt@kernel.org>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Martin Fernandez <martin.fernandez@eclypsium.com>,
	Richard Hughes <hughsient@gmail.com>,
	linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
	platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
	ardb@kernel.org, dvhart@infradead.org, andy@infradead.org,
	gregkh@linuxfoundation.org, rafael@kernel.org,
	akpm@linux-foundation.org, daniel.gutson@eclypsium.com,
	alex.bazhaniuk@eclypsium.com, alison.schofield@intel.com
Subject: Re: [PATCH v3 0/5] x86: Show in sysfs if a memory node is able to do encryption
Date: Tue, 7 Dec 2021 22:06:44 +0200	[thread overview]
Message-ID: <Ya++1FwWzKr2wYQH@kernel.org> (raw)
In-Reply-To: <1ed6020b-f84b-a29b-690a-9eee683c93a6@intel.com>

On Tue, Dec 07, 2021 at 11:52:54AM -0800, Dave Hansen wrote:
> On 12/7/21 11:45 AM, Martin Fernandez wrote:
> >> I wonder, for example, why did you choose per-node reporting rather than
> >> per-region as described in UEFI spec.
> > Some time ago we discussed about this and concluded with Dave Hansen
> > that it was better to do it in this per-node way.
> 
> Physical memory regions aren't exposed to userspace in any meaningful way.

Well, we have /sys/firmware/memory that exposes e820...
 
> An ABI that says "everything is encrypted" is pretty meaningless and
> only useful for this one, special case.
> 
> A per-node ABI is useful for this case and is also useful going forward
> if folks want to target allocations from applications to NUMA nodes
> which have encryption capabilities.  The ABI in this set is useful for
> the immediate case and is useful to other folks.

I don't mind per-node ABI, I'm just concerned that having a small region
without the encryption flag set will render the entire node "not
encryptable". This may happen because a bug in firmware, a user that shoot
themself in a leg with weird memmap= or some hidden gem in interaction
between e820, EFI and memblock that we still didn't discover.

I agree that per-node flag is useful, but maybe we should also have better
granularity as well.

-- 
Sincerely yours,
Mike.

  reply	other threads:[~2021-12-07 20:07 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-03 19:21 [PATCH v3 0/5] x86: Show in sysfs if a memory node is able to do encryption Martin Fernandez
2021-12-03 19:21 ` [PATCH v3 1/5] mm/memblock: Tag memblocks with crypto capabilities Martin Fernandez
2021-12-03 19:21 ` [PATCH v3 2/5] mm/mmzone: Tag pg_data_t " Martin Fernandez
2021-12-03 19:21 ` [PATCH v3 3/5] Tag e820_entry " Martin Fernandez
2021-12-04  8:21   ` Greg KH
2021-12-04 16:05     ` Mike Rapoport
2021-12-03 19:21 ` [PATCH v3 4/5] x86/efi: Tag e820_entries as crypto capable from EFI memmap Martin Fernandez
2021-12-03 19:21 ` [PATCH v3 5/5] drivers/node: Show in sysfs node's crypto capabilities Martin Fernandez
2021-12-04  8:22   ` Greg KH
2021-12-04 16:35     ` Martin Fernandez
2021-12-04 17:22       ` Greg KH
2021-12-04 18:03         ` Martin Fernandez
2021-12-05  6:04 ` [PATCH v3 0/5] x86: Show in sysfs if a memory node is able to do encryption Mike Rapoport
2021-12-06 19:58   ` Richard Hughes
2021-12-07  7:25     ` Mike Rapoport
2021-12-07 19:45       ` Martin Fernandez
2021-12-07 19:52         ` Dave Hansen
2021-12-07 20:06           ` Mike Rapoport [this message]
2021-12-07 20:13             ` Dave Hansen
2021-12-08 14:05       ` Richard Hughes

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