From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 7A4F91F952 for ; Wed, 13 Sep 2023 17:37:26 +0000 (UTC) Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-1c3a2f46244so251115ad.1 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=lists.linux.dev; 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=HQMRxaUjmGSBCztdUuFOecI/HwiBxF/aovUn5vpKW09nvCgiI9jy4kGKF331HAY2rH WtUCfuM4qskOs/UNL4bbpdMo9be2R/gkpcaL7tBrEJD/TCRhdy2keW/1zGLRpOkXDeqo k4SbFRKuMmpWTslPxenwOS2NwDmhTNCI88DjQCBRc+e6h8D3uJvxngSb8r7fWdKb2QZE aGoT1En3tPl7GMokDamZXA+fO9NTpAetKDx3KhJ9vmBXtoMtivKKdGH+6mCuq7WabDCy FGnjscSwvdPkeBmaW/NZYUTNiyLiRcieM+MytJifJoN5+ic4qupxlBxb+UjskS9WR8fF u5HQ== 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=YGXDC6yYTiC3Yv/3bBFHJqFUg5sGGdv1V0VsgFlzfkWWmjjsbiGW5rTwWhDYgNThij PR6PMO+wPKOmADes6H5Qbr5Lz8zWYxjdx2ikYSRRbfkwkw0gwBO/PZj32Rce9KsivLJE +b3y3ZOh8+fj6aECJO9swCW5VoIWavAqb6rD+gdRLPc/83DRyYdz3jZuiX+1As9v7Vwv EWFhzfJkkAnTXg4+wHT1KkIosTB0Lp/3SOeavdJe4wp36jEFrRSx3RpyHLqwbTsNR/w7 xVnjs9tdOIFpw5UTW4TB5w24UyjJ3d4fd5XbwEwyPCvTNQI+Zl0vBnUoh6Cn0zEIvIkY CESQ== X-Gm-Message-State: AOJu0Yypqu1Q0B4KN6JDIzLzGtGxcEctQ2KFGXLHOooi5DIIhS5EMOoV ziSJinzRMLbtKfS/x6X+ubvbrAEAnO8= 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> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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" 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