From patchwork Tue Mar 18 01:33:10 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yan Zhao X-Patchwork-Id: 14020147 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A12BC335C0; Tue, 18 Mar 2025 01:34:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.12 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742261679; cv=none; b=Gnd+UYO4dy99XSEr1ZYFe1QoPWxBj5Rws69JnQ/r1tVlCxYP+2mZACTtWF5vKDZF4quylb1RZjDm3GCwj44hx/Mdgnnp6nFrAJwgKOL5Shpk4s2liOBV0qiShG9aC31RAx9g10IJwBtg9HaDO89+odfuZkQMvkikhYxODhNZ+Rg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742261679; c=relaxed/simple; bh=vvkZUaLrHnUJHGxnetVQdXOSxMK2s/AEG29SSV0tqc0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HFyRPu74Q368/JpSxk710qOnVmBzb1ATaKUGnpek+Pq0MTtjof97S/ivDEDOHkHKsd/EFu2zGeCWJWqVsGrGdjOAmmbbdM77ezsIC0MvXR32lUIXm5lQHSJNx9KoOuqdNKXRI1rRA+G/JEsya2bClQ1cdVUK9i9NhgoRZWwsiWI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Hf+XGVFA; arc=none smtp.client-ip=192.198.163.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Hf+XGVFA" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1742261678; x=1773797678; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=vvkZUaLrHnUJHGxnetVQdXOSxMK2s/AEG29SSV0tqc0=; b=Hf+XGVFA2n5R2d42UH5nolEapapT6OVwgwsU/cUjSGq0WvX/20nOk7A/ 9f/eWw8JndEC9DkPMjamVGaPBr/ZZKaxM4c2yunfecoicc41e1qwBF5WA n+c8wXUTYIwpQmkmCreUQFizl8xpb3DxScQuEl7sdnLHxSiybqopvbpKP hSA9Fsarw9qm5txil1sfYm1LyFp/8oFp1mUCGHPOvjRrsoSpupiMa1baK w+ElmakP0JV7G/QdnltaVpM0adcG5Iyr5rhTqQRw4dXqEv5VzByfAjWv7 zh3Az6G7Cp6C+J0oLiRwUAsr0lwdXZxBMzkDu+Mmh5fhDzRBe0g6HLGCE A==; X-CSE-ConnectionGUID: 9XMKcNb6Tuagua1kwILeGA== X-CSE-MsgGUID: 6tvOL6YPSE2eWUrKlDuNOw== X-IronPort-AV: E=McAfee;i="6700,10204,11376"; a="47269874" X-IronPort-AV: E=Sophos;i="6.14,255,1736841600"; d="scan'208";a="47269874" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by fmvoesa106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2025 18:34:37 -0700 X-CSE-ConnectionGUID: NDAEbuUDR2uGardIrFORsA== X-CSE-MsgGUID: fiedTt/KRaWdBpeKeQapgA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.14,255,1736841600"; d="scan'208";a="122131390" Received: from yzhao56-desk.sh.intel.com ([10.239.159.62]) by fmviesa007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2025 18:34:35 -0700 From: Yan Zhao To: pbonzini@redhat.com, seanjc@google.com Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Yan Zhao Subject: [PATCH v2 4/5] KVM: x86/mmu: Warn if PFN changes on shadow-present SPTE in shadow MMU Date: Tue, 18 Mar 2025 09:33:10 +0800 Message-ID: <20250318013310.5781-1-yan.y.zhao@intel.com> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20250318013038.5628-1-yan.y.zhao@intel.com> References: <20250318013038.5628-1-yan.y.zhao@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Warn if PFN changes on shadow-present SPTE in mmu_set_spte(). KVM should _never_ change the PFN of a shadow-present SPTE. In mmu_set_spte(), there is a WARN_ON_ONCE() on pfn changes on shadow-present SPTE in mmu_spte_update() to detect this condition. However, that WARN_ON_ONCE() is not hittable since mmu_set_spte() invokes drop_spte() earlier before mmu_spte_update(), which clears SPTE to a !shadow-present state. So, before invoking drop_spte(), add a WARN_ON_ONCE() in mmu_set_spte() to warn PFN change of a shadow-present SPTE. For the spurious prefetch fault, only return RET_PF_SPURIOUS directly when PFN is not changed. When PFN changes, fall through to follow the sequence of drop_spte(), warn of PFN change, make_spte(), flush tlb, rmap_add(). Signed-off-by: Yan Zhao --- arch/x86/kvm/mmu/mmu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 94c677f8cc05..607cbb19ea96 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2846,7 +2846,8 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, } if (is_shadow_present_pte(*sptep)) { - if (prefetch && is_last_spte(*sptep, level)) + if (prefetch && is_last_spte(*sptep, level) && + pfn == spte_to_pfn(*sptep)) return RET_PF_SPURIOUS; /* @@ -2860,7 +2861,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, child = spte_to_child_sp(pte); drop_parent_pte(vcpu->kvm, child, sptep); flush = true; - } else if (pfn != spte_to_pfn(*sptep)) { + } else if (WARN_ON_ONCE(pfn != spte_to_pfn(*sptep))) { drop_spte(vcpu->kvm, sptep); flush = true; } else