From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53B5C2E6D1E for ; Wed, 9 Jul 2025 13:55:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752069338; cv=none; b=Psi+oySh/jx8fnEjjpk0Xn2e40DU1Yfy4gNL2rXTa0UH8ERc0HPV253va6NsGNlW9U+WkUw1zn9vhg5YpUf60sUVE4kc+LAEWI3TjGhqqltytnYh1gZ9+3m010rYQLg8C2+Ri6tL1swvgqdxkvPmDq6nTdMn3xGbMLQnt5ld3WA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752069338; c=relaxed/simple; bh=0h9vbjsgJ4KM4kpziRTulPuUJGQOT13eleRpBAru710=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=A8sVCIauD08divPigKi+EL5jKoBBtZPPGidR7VaYDJuK9Pl6pQYvR+6tf1rw/GKWq55JKXPLX6hnTzpj/G8b4gstUvvYLFwSiIh25lnTFz7JotBAdgVeImzu1nSUiigFWCaP+gsHgWUFQStXEXvqdD/nNE8n/9IASMXunspAD/Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=IzOVu1vH; arc=none smtp.client-ip=209.85.216.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="IzOVu1vH" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-3138f5e8ff5so5587402a91.3 for ; Wed, 09 Jul 2025 06:55:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1752069336; x=1752674136; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=hB2pq64+EiT3q+LG5n2vE09OllB22A/8i32Rf86ziks=; b=IzOVu1vHAiZQEW1SK9aITiCIGPOggzl8NHWRVQJBgoLcGSg2u/0on9W2TcDLu6JHny Ugz1GTUMT2tGgQkTI3WJXqTCzVXvsRdVAxrObAnSaMhd3EuRXcWzffk+1eRMuZnrflg0 ATpR7ptMUXiAil3evEELHgLyEEn68SCHZFUsK9zV43w6C5QwBWkO+UV+9Jw9HoZnObYM 8QdAj8VdML8ieYhklbw9GfwqSFBfHsQX5Ef4ADBG0f2MRElJ5Xkxpu78AxA76NEad84e v6OLA75Wu9vSZHwFiBdDMJyzs7+Cm3wFCtms3jO96QwWZcw9NsLmA915hMd+rRDxq7pK b8+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752069337; x=1752674137; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=hB2pq64+EiT3q+LG5n2vE09OllB22A/8i32Rf86ziks=; b=j19YUC009yukzzdTHzTFFcvCKBKhcT/pl3W229Bdu8y5ULqYYlValdnC6qkY0r6JU2 VI2iQ5v7naJDO+pmC7v48OPuQEMHVkaUejDg76BJou0SIZN/a1CmlyvHAuk/EGHIzQWd oD6ZexncGSmr45N4QKfg3G11sxrYHxV4SlgAMl5KEmK+MDiM8DhvGiBzynw4vNXVHURU j+n1cgJ87LH+phwaMjIIdrLpFIEWc/wmB+MLwVeVspLJJMxDVD15q9msaRvowxrDj8w/ yPc2yi90Y6c2GANy6aKG3wKrvYMkDVnVLKVB3TIyJ0YpIYfZwkaO54UlRjZtd3XD0d3J /FOg== X-Forwarded-Encrypted: i=1; AJvYcCWpSBBrL7r2X6REDmI4/Ejv4l0ACuWEJo0cjG5S/8gC79s0UfrRoOjt4xjUnjL7yyR0Y1o=@vger.kernel.org X-Gm-Message-State: AOJu0YwAFF/+i2kpVV4lLXOOKsqqZpW3FFbql4C2XLN0BmY3KPobCkb6 lNwoPY6xPpfI/eh3DIfkGY5vAxBNQwb962/VsKDZFqkYQ02CnGhHfjRXmrFo/XkoD04ZPnbPFYY 5F4GEoQ== X-Google-Smtp-Source: AGHT+IEoqYqG05CCJJatVWyMPh8LvhP8g90wNpXynV+lVfyOqsEL9Ixv2ihGPj+7dKMNBozMlFC5A8s1AoU= X-Received: from pjbta13.prod.google.com ([2002:a17:90b:4ecd:b0:311:ea2a:3919]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:5345:b0:31a:bc78:7fe1 with SMTP id 98e67ed59e1d1-31c3c2d4748mr6038a91.18.1752069336491; Wed, 09 Jul 2025 06:55:36 -0700 (PDT) Date: Wed, 9 Jul 2025 06:55:35 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <1eaa9ba08d383a7db785491a9bdf667e780a76cc.1752038726.git.kai.huang@intel.com> Message-ID: Subject: Re: [PATCH 2/2] KVM: x86: Reject KVM_SET_TSC_KHZ VM ioctl when vCPU has been created From: Sean Christopherson To: Chao Gao Cc: Kai Huang , pbonzini@redhat.com, kvm@vger.kernel.org, thomas.lendacky@amd.com, nikunj@amd.com, bp@alien8.de, isaku.yamahata@intel.com, xiaoyao.li@intel.com, rick.p.edgecombe@intel.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Wed, Jul 09, 2025, Chao Gao wrote: > On Wed, Jul 09, 2025 at 05:38:00PM +1200, Kai Huang wrote: > >Reject the KVM_SET_TSC_KHZ VM ioctl when there's vCPU has already been > >created. > > > >The VM scope KVM_SET_TSC_KHZ ioctl is used to set up the default TSC > >frequency that all subsequent created vCPUs use. It is only intended to > >be called before any vCPU is created. Allowing it to be called after > >that only results in confusion but nothing good. > > > >Note this is an ABI change. But currently in Qemu (the de facto > >userspace VMM) only TDX uses this VM ioctl, and it is only called once > >before creating any vCPU, therefore the risk of breaking userspace is > >pretty low. > > > >Suggested-by: Sean Christopherson > >Signed-off-by: Kai Huang > >--- > > arch/x86/kvm/x86.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > >index 699ca5e74bba..e5e55d549468 100644 > >--- a/arch/x86/kvm/x86.c > >+++ b/arch/x86/kvm/x86.c > >@@ -7194,6 +7194,10 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) > > u32 user_tsc_khz; > > > > r = -EINVAL; > >+ > >+ if (kvm->created_vcpus) > >+ goto out; > >+ > > shouldn't kvm->lock be held? Yep.