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 E1BEE2505B1 for ; Mon, 10 Feb 2025 22:23:40 +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=1739226222; cv=none; b=oaAK3ZpClHS3/h2NqIKXKPXNTSw0HQkKWmVtq0IBLvP0vc9mZPKyuBbiE3y61/MLfhSSLBDAYdqvCkjNWf8ghU8fh5QolcKgDtHZZDuDmCj17kPwp3cFnl7djJ7Y7TuUxdvun6A+H6YAKyPPfCC/wpjNXVUk7fZbbdLU17okLYI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739226222; c=relaxed/simple; bh=hF8Vf4v4gr1R+Shd48LsTyb/BYZwoN0AaP4YvUCD6FU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=N6sG52zNh6u1vEAAGLsVPBiQ3ANHK0dVQ/NdCaxADf4ydaQTI78aUlLAk5VzDsDbxTdUsTHVpDH7Di9FBso5GT0Ccps0rNpPIrol01rysv5UqkwGjWcbkAvQCmHk12FAETjp7Bxan+qRtNISmap+LWl+XK2OrhWpnFpHgqdqnSs= 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=4c/Gi0Pz; 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="4c/Gi0Pz" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-2fa1e63a5ffso13542233a91.3 for ; Mon, 10 Feb 2025 14:23:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1739226220; x=1739831020; 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=pUXvYzG8eRKf2w27XFFoCbVFPZhMAFQZ2tlWsem28oM=; b=4c/Gi0PzVH8a9EgDCiqitnq8V4knhIxPHxi0eLI/uVXtuqLMYY8ZaWLXZS8g0KxtHU oph7inMFINU2v/IINGVFmiGkV5PmUM6jOcFmseBRlmyPaqJBc08XKeujNLWafnPUQd79 WLzG7Ngq54f052sQi1i+GmMuIVLo5AcOv5deboj/oR9Zdf+dePcOooHebU8WK6oLCnGp Vl8F90a/KJut6ytynnRpTUH2y5m5N2emPwVkZM+aeWyqV3+R6iBrOuDLKtVsj25H1SGc 3/DeVNbAKaQzco+1MFWXaWmXZU9/dKT57o4nMMrpXHBx9i33yj70bmA38VkDigPAgC/7 +h4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739226220; x=1739831020; 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=pUXvYzG8eRKf2w27XFFoCbVFPZhMAFQZ2tlWsem28oM=; b=R8Z936wKQ8vCkYlBky6+6AR8dJPh2v5NNYkTIGzFTPBUGlRkxvS78LMWWwcffAn9ZS s3r31Dc2qz+VNZOHqRVQJB9pTsRyodeZiTUAzN/ghfjmhQoIiDozEpBVwjYvFo1sUenl egw5tSSI4kIAldfum/Pujs6raiH/QbSnlSrVlgT5Ja8SmtJKBkGp1KzAEdWNAn6Nzqxq hUGUtX35Yf9LApT/OuffBImS/Y+PdG7Togp+crVVr9aU4VHq0xTKawJvxQFSmGmffcAj u/yjhcFwSRnnc9WD8N4Ts0oTubK+NFA6aSxpA9speF+ZJOnrbINkYTQnMwzHFhEkgzk8 sRUA== X-Forwarded-Encrypted: i=1; AJvYcCWBl+M4T9/yUZDo8JcGnpQNSsHKI92RrWRkIx1pycBizCPlP4JNVVef41PS7mD34w5iKM4=@vger.kernel.org X-Gm-Message-State: AOJu0Yz2H2Mb5OnL5KwENs+dxejePK5hVzm1JRwigrq5vsEi9uw5wFeu m01QhG8mkAyIwwcvaY/UCLjYHLMd2/p9ho15ISMDfcd3q5WSCvzt7PsBrAZaznFFe/uTe8ZPZMP kdg== X-Google-Smtp-Source: AGHT+IEy3+bVFo6JcMsoWvq+cYL38XbyKOeuF/tQSdUVXK2R0Wk67Xr5wVNUmJlCk3rS7iPBAN0yLqQOGnk= X-Received: from pfmu14.prod.google.com ([2002:aa7:838e:0:b0:730:9617:a4c9]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:3989:b0:730:f1b7:9bb2 with SMTP id d2e1a72fcca58-730f1b79cfdmr3734751b3a.13.1739226220172; Mon, 10 Feb 2025 14:23:40 -0800 (PST) Date: Mon, 10 Feb 2025 14:23:38 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250207030640.1585-1-yan.y.zhao@intel.com> <20250207030900.1808-1-yan.y.zhao@intel.com> Message-ID: Subject: Re: [PATCH 3/4] KVM: x86/mmu: Make sure pfn is not changed for spurious fault From: Sean Christopherson To: Yan Zhao Cc: pbonzini@redhat.com, rick.p.edgecombe@intel.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Sat, Feb 08, 2025, Yan Zhao wrote: > On Fri, Feb 07, 2025 at 07:07:06AM -0800, Sean Christopherson wrote: > > On Fri, Feb 07, 2025, Yan Zhao wrote: > > > Make sure pfn is not changed for a spurious fault by warning in the TDP > > > MMU. For shadow path, only treat a prefetch fault as spurious when pfn is > > > not changed, since the rmap removal and add are required when pfn is > > > changed. > > > > I like sanity checks, but I don't like special casing "prefetch" faults like this. > > KVM should _never_ change the PFN of a shadow-present SPTE. The TDP MMU already > > BUG()s on this, and mmu_spte_update() WARNs on the transition. > However, both TDP MMU and mmu_set_spte() return RET_PF_SPURIOUS directly before > the BUG() in TDP MMU or mmu_spte_update() could be hit. Ah, that's very different than treating a prefetch fault as !spurious though. I would be a-ok with this: if (is_shadow_present_pte(iter->old_spte) && (fault->prefetch || is_access_allowed(fault, iter->old_spte)) && is_last_spte(iter->old_spte, iter->level)) { WARN_ON_ONCE(fault->pfn != spte_to_pfn(iter->old_spte)); return RET_PF_SPURIOUS; }