From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (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 A5CABCA4E for ; Wed, 6 Mar 2024 22:43:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709765037; cv=none; b=KwLaGWy9Ecjq6GTP+S7iobc1k8WqpFDn2pVw598SdS0NzU+NSpVrVPDm/9yg0u9rbdsXbIXhyp94T0N0D5YKe68rnngYaw/tJwiZfX2l9ZeN0+sd0lbDjYXWwZ4ymJpHNUvyO2FAlX9D8JhLc2vmVsTG8tyR0+4NcdCKR5whuZo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709765037; c=relaxed/simple; bh=/HhmgHY9Vyo2JQaInrFC98id0ADUFYLs567EtUvXnXw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=u+hzYfmeSqY9d25S6ihVoz5nzzqZMWUlCtZbQLQDqbpaC/HjiO82XGLEuiLR2/mDfU5Bal8Plf2HgYJH7m//hIui+43xVVjPjy6MkhUkxEsKTy4uRjOT8wvY0mvyNBA5vT/YaMNt4NNNIS/OSYCLwz/Ftf/Qs96ad5UO1lq0Okw= 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=a0QuFOVj; arc=none smtp.client-ip=209.85.128.202 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="a0QuFOVj" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-607e613a1baso5491317b3.1 for ; Wed, 06 Mar 2024 14:43:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1709765034; x=1710369834; 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=kYeF/kACf7fpncWg98H8xfi7RXLHudnXWCpEy+NEJ2g=; b=a0QuFOVjcDcIIAy4T76L90YwKpTits+1HtAvGasuZR2unuVp75Egd+4kwtib2nLUaC VoB1fycOqjd6YrnpgzRr0HqQFSdW1lbbgbP1vOa6pvAukRTds96OJ+kWK85oZZ1sxPMR pgNgdpinDnYc6CO12RgccF9E9G6l8+afE3T31EYhnMhTBTt/sUsIOf3spAFZX/GOed6W y4hzlM1tjWEtrHxGmbe1NVXbj28A+2lnyHcQLPdRp46pDO9iAUldeNbSBkmYNlzHLpQY 1ERBp7nniX2VvEdOqSj70JMowNY55zxC92osIAaUO5UpKUD8U3rbpRIH87b+vspwn8u+ BfeA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709765034; x=1710369834; 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=kYeF/kACf7fpncWg98H8xfi7RXLHudnXWCpEy+NEJ2g=; b=L1y5d3fk7nrSQQeCZXeFRGU4cNE3zy4tq+v1nU+V5toV4IMyGJ+DDQ4oWBxue1Klx2 VTQebEb0f4gZNRAGoysICBoUBaCDefWZYnNMrjyA9ggXwKVrQ4g0pz/4M2T2EYgbSgSl 9w1mljWcw/mCluWYeFN8L/62YldDCBRBCLBbDHgy6fj/OKvX2i5kxgiJFIACye+XQbZW qAdQWwPX9G7xzbA7vuasjAfZnZuqyHtHUeaZpJVR4yAnnY3inrrklOtTHjsBkVun6lq2 BsBHcM+4lPjGuLNNxg+7CTwbceeIOb+lTG1lci24blG5d3bcTvQaQB6m5MOFGvSqH5OL 4T3Q== X-Forwarded-Encrypted: i=1; AJvYcCUjS3rgE5+U0LDQu/Ht7CXjT5/1QT+TqJIMHZotueMyreLRl2/xLyFm46VLWPRK5pIhEdwf+7v0e1qEAT2xCPsZXOLL X-Gm-Message-State: AOJu0YwriHz4iLT+4zCzUHhmpX+62zq7yHi2PhIDIOBLohKo+4wfUr8i 3sABQidKsa2nM1RrostwrfgTWyXaTNxJW1dM/YV15WM/r4cTXXv/F3OGcH+65Sg070/Pkjxw3T/ Jqg== X-Google-Smtp-Source: AGHT+IE0lG2XpGXkBwtp0+gcBIrfYiqpLawDQO9qlP+0KYjaaDjD9LVzh573CU0NXKCcbck1ASNBIpC3STo= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:110a:b0:dc7:49a9:6666 with SMTP id o10-20020a056902110a00b00dc749a96666mr4059310ybu.3.1709765034707; Wed, 06 Mar 2024 14:43:54 -0800 (PST) Date: Wed, 6 Mar 2024 14:43:53 -0800 In-Reply-To: <0a05d5ec-5352-4bab-96ae-2fa35235477c@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240228024147.41573-1-seanjc@google.com> <20240228024147.41573-12-seanjc@google.com> <0a05d5ec-5352-4bab-96ae-2fa35235477c@intel.com> Message-ID: Subject: Re: [PATCH 11/16] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO From: Sean Christopherson To: Kai Huang Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yan Zhao , Isaku Yamahata , Michael Roth , Yu Zhang , Chao Peng , Fuad Tabba , David Matlack Content-Type: text/plain; charset="us-ascii" On Thu, Mar 07, 2024, Kai Huang wrote: > > > On 28/02/2024 3:41 pm, Sean Christopherson wrote: > > Explicitly detect and disallow private accesses to emulated MMIO in > > kvm_handle_noslot_fault() instead of relying on kvm_faultin_pfn_private() > > to perform the check. This will allow the page fault path to go straight > > to kvm_handle_noslot_fault() without bouncing through __kvm_faultin_pfn(). > > > > Signed-off-by: Sean Christopherson > > --- > > arch/x86/kvm/mmu/mmu.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index 5c8caab64ba2..ebdb3fcce3dc 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -3314,6 +3314,11 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu, > > { > > gva_t gva = fault->is_tdp ? 0 : fault->addr; > > + if (fault->is_private) { > > + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); > > + return -EFAULT; > > + } > > + > > As mentioned in another reply in this series, unless I am mistaken, for TDX > guest the _first_ MMIO access would still cause EPT violation with MMIO GFN > being private. > > Returning to userspace cannot really help here because the MMIO mapping is > inside the guest. That's a guest bug. The guest *knows* it's a TDX VM, it *has* to know. Accessing emulated MMIO and thus taking a #VE before enabling paging is nonsensical. Either enable paging and setup MMIO regions as shared, or go straight to TDCALL. > > I am hoping I am missing something here?