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 650081FF0E5 for ; Wed, 15 Jul 2026 14:20:57 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 379092142F; Wed, 15 Jul 2026 14:20:57 +0200 (CEST) Message-ID: Date: Wed, 15 Jul 2026 14:20:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH-SERIES qemu-server v3 0/4] cpu config: enable hv-evmcs for Windows 11/2022/2025 to mitigate issues with VBS To: Fiona Ebner References: <20260714104201.71308-1-f.ebner@proxmox.com> Content-Language: en-US From: Jonas Theisen In-Reply-To: <20260714104201.71308-1-f.ebner@proxmox.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1784118034539 X-SPAM-LEVEL: Spam detection results: 0 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: OAD5QO7EGXD5CGU3BHQMYUNZ2ZZWDOQW X-Message-ID-Hash: OAD5QO7EGXD5CGU3BHQMYUNZ2ZZWDOQW X-MailFrom: j.theisen@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 7/14/26 12:41, Fiona Ebner wrote: > 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 > > [...] Tested the patch on an affected Intel machine with q35 Windows Server 2025 VMs. Bumping the machine version to 11.0-pve2 fixes the issue while the previously available 11.0-pve1 stays unchanged. Tested-by: Jonas Theisen