From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AB0F5CCFA05 for ; Fri, 7 Nov 2025 10:00:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vHJGM-0004QQ-4t; Fri, 07 Nov 2025 05:00:10 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vHJGK-0004Q1-0L for qemu-devel@nongnu.org; Fri, 07 Nov 2025 05:00:08 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vHJGG-0004fQ-R4 for qemu-devel@nongnu.org; Fri, 07 Nov 2025 05:00:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762509602; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=Dmmv2c/Zhjm4ukamgxhQU+o21mAuVZsjrQ062leqzZw=; b=RIQVrnQ1g+eXGDfm9757/2eKe2mHzah9kWumACfi9qhb2TpMCruI8gGN/85bUfrsBe7SpD EQIXwhrauB+D0Ow1l+zTSrUBW7H8DIt8hVk1CBSoGu1ZlzeyJ0P7beofu2lIwzYztOnA6Y R4bgOM0xAUrlwDAyXhsV+E2zgShQzIk= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-296-84zePJ-aOMS3teb0xAYc7Q-1; Fri, 07 Nov 2025 04:59:59 -0500 X-MC-Unique: 84zePJ-aOMS3teb0xAYc7Q-1 X-Mimecast-MFC-AGG-ID: 84zePJ-aOMS3teb0xAYc7Q_1762509597 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4926519560B5; Fri, 7 Nov 2025 09:59:57 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.108]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 829AF19560A7; Fri, 7 Nov 2025 09:59:51 +0000 (UTC) Date: Fri, 7 Nov 2025 09:59:46 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Naveen N Rao Cc: Markus Armbruster , qemu-devel , Paolo Bonzini , Eduardo Habkost , Eric Blake , Marcelo Tosatti , Zhao Liu , Nikunj A Dadhania , Tom Lendacky , Michael Roth , Roy Hopkins , Srikanth Aithal Subject: Re: [PATCH v3 8/9] target/i386: SEV: Add support for setting TSC frequency for Secure TSC Message-ID: References: <87cy5vgy66.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.271, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Nov 07, 2025 at 02:21:24PM +0530, Naveen N Rao wrote: > On Thu, Nov 06, 2025 at 01:09:37PM +0100, Markus Armbruster wrote: > > Pardon my ignorance... > > > > "Naveen N Rao (AMD)" writes: > > > > > Add support for configuring the TSC frequency when Secure TSC is enabled > > > in SEV-SNP guests through a new "tsc-frequency" property on SEV-SNP > > > guest objects, similar to the vCPU-specific property used by regular > > > guests and TDX. > > > > Which property exactly? > > Same name: tsc-frequency specified with '-cpu' > > > > > > A new property is needed since SEV-SNP guests require > > > the TSC frequency to be specified during early SNP_LAUNCH_START command > > > before any vCPUs are created. > > > > Sounds awkward. > > > > Do the two properties set the same thing at different times? > > Yes. For regular guests, TSC frequency is set using a vCPU ioctl. > However, TDX and SEV-SNP (with Secure TSC) require the TSC frequency to > be set as a VM property (there is a VM ioctl for this purpose). The '-cpu' arg is global to the VM, so even though the ioctl is per-VCPU, a single '-cpu ...,tsc-frequency=NNN' argument applies universally to all the vCPUs in regular guests. > This was Tom's question too (see v2): is there any way to re-use > 'tsc-frequency' specified with '-cpu' for Secure TSC. I see no reason why we can't simply use the existing '-cpu tsc-frequency' value. Fetch the CPU 0 object and query its "tsc-frequency" property, and just assume all non-0 CPUs have the same tsc-frequency, since we don't provide a way to set it differently per-CPU IIUC. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|