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 B52DC1FF0E5 for ; Wed, 15 Jul 2026 13:47:10 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id E8F4A213EC; Wed, 15 Jul 2026 13:47:09 +0200 (CEST) From: Maximiliano Sandoval To: Fiona Ebner Subject: Re: [PATCH-SERIES qemu-server v3 0/4] cpu config: enable hv-evmcs for Windows 11/2022/2025 to mitigate issues with VBS In-Reply-To: <20260714104201.71308-1-f.ebner@proxmox.com> (Fiona Ebner's message of "Tue, 14 Jul 2026 12:41:47 +0200") References: <20260714104201.71308-1-f.ebner@proxmox.com> User-Agent: mu4e 1.12.9; emacs 30.1 Date: Wed, 15 Jul 2026 13:46:34 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1784115976614 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.314 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: EJS6OVI7ACGVOY733C3S4ZG4GI52IXCP X-Message-ID-Hash: EJS6OVI7ACGVOY733C3S4ZG4GI52IXCP X-MailFrom: m.sandoval@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: Fiona Ebner writes: > Changes in v3: > * Improve commit message in patch 1. > * Different approach, enable recommended hv-evmcs flag instead of > disabling apicv flags. > * Mock host CPU vendor in tests. > > Changes in v2: > * Disable MBEC by default for machine versions < 11.0 for backwards > compat with older kernel and QEMU. > > As reported in the community forum [0] and enterprise support, Windows > with MBEC and VBS can have issues on certain Intel CPUs, leading to > guest freezes and 100% CPU usage. The detection/enabling of APICv > support in Windows was determined to be related. With hv_emcs, that > feature is not used in Windows anymore. The flag is also recommended > in the QEMU documentation [1], so start using it with a bumped > 11.0+pve2 machine version. > > [0]: https://forum.proxmox.com/threads/184178 > [1]: https://www.qemu.org/docs/master/system/i386/hyperv.html#recommendations > > [..] I tested this direction on my host with a AMD CPU as a smoke test and updated the machine version from three Windows VMs from 10.1 to 11.0+pve2 (two were using i440fx and the third q35) from the web UI and the VMs boot as expected. The windows versions were 2019, 2016, and 2022. I also tried with a Linux VM. The code looks OK to me. Tested-by: Maximiliano Sandoval Reviewed-by: Maximiliano Sandoval -- Maximiliano