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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C414BEE01F4 for ; Wed, 13 Sep 2023 17:37:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231233AbjIMRhb (ORCPT ); Wed, 13 Sep 2023 13:37:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230347AbjIMRha (ORCPT ); Wed, 13 Sep 2023 13:37:30 -0400 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 327ADB8 for ; Wed, 13 Sep 2023 10:37:26 -0700 (PDT) Received: by mail-pl1-x649.google.com with SMTP id d9443c01a7336-1bf39e73558so162635ad.2 for ; Wed, 13 Sep 2023 10:37:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1694626645; x=1695231445; 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=1AecudT7EiX+/N1zd76G2BuWYAX0/KYuLLaU2H3llYQ=; b=U8BIABw/cNPFs1/y98w03BSd9X0/5LBkjSaM7PWjP1lf52AeXYmdsxMMCDIz6hXa9J O64a4RZhv0YQ3BiVTjffp97ynknGRZElnjkGr6EfygfgPyDWFx1QYt71Wcpz1ejZ9Bst zNVW+z5s8s9r8YL1KD23dY8TRleIJOSifu8nXp79vKxwmtKJu6tCxDnhUXAiENhjm5up w4+5eKwXnesDhFknxdmXA8XU2mbH2y/OfYlPYIOWcPR0xeUBUNWwHARPbKracOS+Jfa4 htlxgUEOMLmfR0z8nr7z3TDKiWoFdRkT5hOg+puL7WSdEG5PV630yUkK5mLoek/K+tEQ Icfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694626645; x=1695231445; 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=1AecudT7EiX+/N1zd76G2BuWYAX0/KYuLLaU2H3llYQ=; b=DMJLkY9kB8HZTRk4O1j1RU7N5BdgVxPnXtGq5bj1JyzF10iywVcAO8OyMrZoK52Ln4 xPQiFyIdOhaQjte+uocLqy8ikt28UuejNBGJte30D1/nUyO0fDwUH/JBfBfbihzAvWFX dLUeaxpPI2m43vysuAqQHWAFCU2klplU/zLNU2HX6BuZO7tqEXELXIz6DQHiXyntJY9b Tiv0NJ7dPIHP0/E9ALJdBE/5jA74tKlG7lHNrsoJKBM4cIxqGzi7Go+PEB2Jqmp6F/zG xR0+6ZrhaBDiESdvuk4Fb2DBktPgb6tmpQrE0LuNWncs2hbvpigrfkIOwlswHbtr8K/p m+1Q== X-Gm-Message-State: AOJu0YzTwbwsRqugoFAo01iTPHLGm8yxsVhcuf3iluiJ4tHnKS5doz96 Ji628aJG52x1KPfXvnxgqYQdRZ6Zl14= X-Google-Smtp-Source: AGHT+IHiMeIl2kyTkgSOGsBoH7eXEckogjT+Oxb3QtAWLG1MtxlYB2PHOPs6XjcZ/s4JwKMi4FJkjjeo9Jg= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90a:c28b:b0:26b:2001:54f5 with SMTP id f11-20020a17090ac28b00b0026b200154f5mr76310pjt.8.1694626645628; Wed, 13 Sep 2023 10:37:25 -0700 (PDT) Date: Wed, 13 Sep 2023 10:37:24 -0700 In-Reply-To: <36f6fae6cd7aaba3b0fc18f10981bbba2c30b979.1694599703.git.isaku.yamahata@intel.com> Mime-Version: 1.0 References: <36f6fae6cd7aaba3b0fc18f10981bbba2c30b979.1694599703.git.isaku.yamahata@intel.com> Message-ID: Subject: Re: [RFC PATCH 3/6] KVM: guest_memfd, x86: MEMORY_FAULT exit with hw poisoned page From: Sean Christopherson To: isaku.yamahata@intel.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com, Michael Roth , Paolo Bonzini , erdemaktas@google.com, Sagi Shahar , David Matlack , Kai Huang , Zhi Wang , chen.bo@intel.com, linux-coco@lists.linux.dev, Chao Peng , Ackerley Tng , Vishal Annapurve , Yuan Yao , Jarkko Sakkinen , Xu Yilun , Quentin Perret , wei.w.wang@intel.com, Fuad Tabba Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 13, 2023, isaku.yamahata@intel.com wrote: > From: Isaku Yamahata > > When resolving kvm page fault and hwpoisoned page is given, KVM exit > with HWPOISONED flag so that user space VMM, e.g. qemu, handle it. > > - Add a new flag POISON to KVM_EXIT_MEMORY_FAULT to indicate the page is > poisoned. > - Make kvm_gmem_get_pfn() return hwpoison state by -EHWPOISON when the > folio is hw-poisoned. > - When page is hw-poisoned on faulting in private gmem, return > KVM_EXIT_MEMORY_FAULT with HWPOISONED flag. > > Signed-off-by: Isaku Yamahata > --- ... > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index eb900344a054..48329cb44415 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -527,7 +527,8 @@ struct kvm_run { > } notify; > /* KVM_EXIT_MEMORY_FAULT */ > struct { > -#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3) > +#define KVM_MEMORY_EXIT_FLAG_PRIVATE BIT_ULL(3) > +#define KVM_MEMORY_EXIT_FLAG_HWPOISON BIT_ULL(4) Rather than add a flag, I think we should double down on returning -1 + errno when exiting with vcpu->run->exit_reason == KVM_EXIT_MEMORY_FAULT, as is being proposed in Anish's series for accelerating UFFD-like behavior in KVM[*]. Then KVM can simply return -EFAULT or -EHWPOISON to communicate why KVM is existing at a higher level, and let the kvm_run structure provide the finer details about the access itself. E.g. kvm_faultin_pfn_private() can simply propagate the return value from kvm_gmem_get_pfn() without having to identify *why* kvm_gmem_get_pfn() failed. static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { int max_order, r; if (!kvm_slot_can_be_private(fault->slot)) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return -EFAULT; } r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn, &max_order); if (r) { kvm_mmu_prepare_memory_fault_exit(vcpu, fault); return r; } ... } [*] https://lore.kernel.org/all/20230908222905.1321305-5-amoorthy@google.com