From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [45.144.208.40]) by lore.proxmox.com (Postfix) with ESMTPS id 7EB291FF0ED for ; Fri, 31 Jul 2026 10:09:53 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id C1B242132B; Fri, 31 Jul 2026 10:09:52 +0200 (CEST) Date: Fri, 31 Jul 2026 10:09:46 +0200 From: Arthur Bied-Charreton To: Fiona Ebner Subject: Re: [RFC qemu/qemu-server 0/2] qemu: dump and ship CPU model expansions Message-ID: References: <20260730141522.203966-1-f.ebner@proxmox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260730141522.203966-1-f.ebner@proxmox.com> X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1785485377824 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.763 Adjusted score from AWL reputation of From: address DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment (newer systems) RCVD_IN_DNSWL_LOW -0.7 Sender listed at https://www.dnswl.org/, low trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: D7VYIHKRLTZU2JWCOK6R4ORVNQZZSXV5 X-Message-ID-Hash: D7VYIHKRLTZU2JWCOK6R4ORVNQZZSXV5 X-MailFrom: a.bied-charreton@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: pve-devel@lists.proxmox.com X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu, Jul 30, 2026 at 04:15:08PM +0200, Fiona Ebner wrote: > Sending this, so Arthur and Erik can look into it for issue #7841. > > Having the CPU model expansions readily available makes it possible to > be precise when checking for the presence of certain CPU flags or > properties. For example, the pdpe1gb flag is relevant since OVMF will > limit the phys-bits to 40 without that. Starting a QEMU process to > query this via QMP is too costly in many cases, so qemu-server is > currently limited to use heuristics. > > Having the flags can also be useful for the custom CPU model editor to > show what the default value for a given flag and model actually is. > > The one for x86_64 is rather large with 1.65 MiB, but it can be loaded > on first use and then cached by the CPUConfig.pm module. > > It's important to be aware that some features/flags are gated behind > others, most prominently, the nested virtualization ones. > Thanks for sending this! Wouldn't it make more sense to build this directly in such a way that we can query model expansions dynamically though? As far as I can tell, gated flags mean that, as soon as a CPU config has one flag set/unset (which I think is a pretty common case), we cannot rely on the static file anymore. There might be a way to find out which features gate others, but this seems like a workaround that could be avoided entirely with dynamic queriability. What do you think? > pve-qemu: > > Fiona Ebner (1): > d/rules: dump and ship CPU model expansions > > debian/cpu-model-expansions-aarch64.json | 220 + > debian/cpu-model-expansions-x86_64.json | 51268 +++++++++++++++++++++ > debian/dump-cpu-model-expansions.pl | 66 + > debian/rules | 10 + > 4 files changed, 51564 insertions(+) > create mode 100644 debian/cpu-model-expansions-aarch64.json > create mode 100644 debian/cpu-model-expansions-x86_64.json > create mode 100755 debian/dump-cpu-model-expansions.pl > > > qemu-server: > > Fiona Ebner (1): > cpu flags: introduce get_cpu_model_expansions() helper > > src/PVE/QemuServer/CPUFlags.pm | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > > Summary over all repositories: > 5 files changed, 51591 insertions(+), 0 deletions(-) > > -- > Generated by git-murpp 0.5.0 > > > >