From: "Michael S. Tsirkin" <mst@redhat.com>
To: Kevin Loughlin <kevinloughlin@google.com>
Cc: "David Hildenbrand" <david@kernel.org>,
"Jason Wang" <jasowangio@gmail.com>,
"Eugenio Pérez" <eperezma@redhat.com>,
"Xuan Zhuo" <xuanzhuo@linux.alibaba.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Kiryl Shutsemau" <kas@kernel.org>,
"Thomas Gleixner" <tglx@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Ashish Kalra" <ashish.kalra@amd.com>,
"Michael Roth" <michael.roth@amd.com>,
"Rick Edgecombe" <rick.p.edgecombe@intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Vlastimil Babka" <vbabka@kernel.org>,
"Mike Rapoport" <rppt@kernel.org>,
"Suren Baghdasaryan" <surenb@google.com>,
"Michal Hocko" <mhocko@suse.com>,
"Brendan Jackman" <brendan.jackman@linux.dev>,
"Johannes Weiner" <hannes@cmpxchg.org>, "Zi Yan" <ziy@nvidia.com>,
"Alexander Duyck" <alexanderduyck@fb.com>,
virtualization@lists.linux.dev, linux-coco@lists.linux.dev,
linux-efi@vger.kernel.org, linux-mm@kvack.org,
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"Sidharth Telang" <sidtelang@google.com>,
"Punit Salian" <psalian@google.com>,
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"Ackerley Tng" <ackerleytng@google.com>,
"Jacky Li" <jackyli@google.com>,
"Steve Rutherford" <srutherford@google.com>,
"David Skidmore" <davidskidmore@google.com>
Subject: Re: [PATCH 00/13] virtio_balloon, efi/unaccepted: support memory ballooning and free page reporting in CoCo guests
Date: Tue, 27 Oct 2026 06:29:29 -0400 [thread overview]
Message-ID: <20261027051245-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20261027025616.1632690-1-kevinloughlin@google.com>
On Tue, Oct 27, 2026 at 02:56:03AM +0000, Kevin Loughlin wrote:
> This series enables virtio-balloon free page reporting and memory balloon
> inflation/deflation in Confidential Computing (CoCo) guests, starting
> with architectural hooks implemented for AMD SEV variants, in order to
> support dynamic CoCo guest resizing.
>
> Today, memory ballooning and free page reporting are essentially unusable
> in CoCo guests due to three main roadblocks:
For me, the bigger question is not whether we can, but whether we
should. Considerations I would like to see addressed:
Security, e.g.: does knowing which memory is free leak information from
the guest? If no, why not?
Consider CONFIG_SHUFFLE_PAGE_ALLOCATOR, RANDSTRUCT, etc.
correctness, e.g.: Linux has init on free (and default on windows), if
initialized pages are dropped and host can not be trusted, they have to be
re-initialized. Is this handled? I don't see it in code.
Also, performance, e.g.: How much does this re-initialization cost?
Management: it was simple with balloon off unconditionally.
Now we are in murkier waters with various features offering
various performance/security tradeoffs.
What if some guests want the tradeoffs but others don't?
Documentation: for all of the above.
--
MST
next prev parent reply other threads:[~2026-10-27 10:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-27 2:56 [PATCH 00/13] virtio_balloon, efi/unaccepted: support memory ballooning and free page reporting in CoCo guests Kevin Loughlin
2026-10-27 2:56 ` [PATCH 01/13] virtio_ring: support per-virtqueue DMA mapping ops Kevin Loughlin
2026-10-27 9:42 ` Michael S. Tsirkin
2026-10-27 2:56 ` [PATCH 02/13] virtio_balloon: add reporting_vq DMA map ops Kevin Loughlin
2026-10-27 2:56 ` [PATCH 03/13] x86/coco/sev: add snp_unaccept_memory() Kevin Loughlin
2026-10-27 2:56 ` [PATCH 04/13] x86/coco/sev: fix zeropad #VC on unaccepted memory Kevin Loughlin
2026-10-27 2:56 ` [PATCH 05/13] efi/libstub: start unaccepted bitmap at address 0 Kevin Loughlin
2026-10-27 2:56 ` [PATCH 06/13] efi/unaccepted: add mark_memory_unaccepted() Kevin Loughlin
2026-10-27 2:56 ` [PATCH 07/13] mm/page_alloc: allow lower-order unaccepted_pages Kevin Loughlin
2026-10-27 2:56 ` [PATCH 08/13] mm/page_alloc: route unaccepted isolated pages Kevin Loughlin
2026-10-27 2:56 ` [PATCH 09/13] mm/page_reporting: account for unaccepted memory Kevin Loughlin
2026-10-27 2:56 ` [PATCH 10/13] virtio_balloon: add higher-order page inflation Kevin Loughlin
2026-10-27 9:35 ` Michael S. Tsirkin
2026-10-27 9:36 ` Michael S. Tsirkin
2026-10-27 2:56 ` [PATCH 11/13] virtio_balloon: unaccept free reporting ranges Kevin Loughlin
2026-10-27 2:56 ` [PATCH 12/13] virtio_balloon: unaccept inflated balloon pages Kevin Loughlin
2026-10-27 2:56 ` [PATCH 13/13] virtio_balloon: enforce ACCESS_PLATFORM in CoCo Kevin Loughlin
2026-10-27 10:29 ` Michael S. Tsirkin [this message]
2026-10-27 20:39 ` [PATCH 00/13] virtio_balloon, efi/unaccepted: support memory ballooning and free page reporting in CoCo guests Michael S. Tsirkin
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