From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 458B037572A for ; Thu, 30 Oct 2025 20:10:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761855009; cv=none; b=ZSSshwaAB1rwwxEsxBIptzzVPJeMGfOtqDxkooOYWZptIiushbuzC2oDhKvB66E3cR3OmZtbZewvKVw2fc2hUe1x4h+KGPyxlH/jmLW6Z1LAYNlWvD2pzKDE4vwkUGEqWxVdzlvfzFR0fs86waCh7De75WZ6gqv+GKPsoGuL3uI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761855009; c=relaxed/simple; bh=MUDH20eIOuOTsz0KS9uuqL90AQHBBTqkmMlPBeDR0dg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=T//l0+40z6HovReWtdOH5YU2w1NekZU6V7l25VdocAAvpMMZV3S/Eb/Av8lP+ICdMHCndY8hPzuRPzHMGcq4TXC/3q4yrZ9SvzUWpI+GxYTRfc0QaAFKYHCg9LcxcIIG3vFlLBNHUAHBAX3n39zxP2bGmsXNMONPlm4mID/SL/8= 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=3Nd5CoHe; arc=none smtp.client-ip=209.85.214.201 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="3Nd5CoHe" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-294baa12981so19216705ad.1 for ; Thu, 30 Oct 2025 13:10:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1761855007; x=1762459807; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=TnV5Uo4WEDSyHqNRydChmPWwv04NNnacTlgMSv81cvQ=; b=3Nd5CoHeItZGRm7DOBKuDtrJVtAJjhbPMXsbdHY9zoPZdc+j5R/BdFXK4bkWcBnMzK iwpvAP/zsvxs8ul1OMze+b01Bbxnq6HyKl6NjBeI2XQj+Q+gY/vQOuFIbzYLaV6+k4Ks ySdkgOIuaIg0itHWf8IHmtKahW0rV427n6G9xYt+h94YBBQiUFiqK+6RtA09wrXYN7SF OVviFkTBZIUhQun0btCRNygOdXpD0tioc1A4NGQSRztDQ+qoiAhX14sMaMZpEjRdxNr8 Wfaq+q5Z9ormV3Zy6qZn1hwo0o20J/58CIs6R8aefyskrnEsxE8zvaSrbXj9fzRGtjWt nArg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761855007; x=1762459807; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=TnV5Uo4WEDSyHqNRydChmPWwv04NNnacTlgMSv81cvQ=; b=HRmiiw8dhKgPN7WXcVqzCrb7LKnOQpiT86VDD8xJy/eP4AwyoR5fWdxvrn1W8x7Pwy PAN0G9OuTaoA7i1+Cdd+idUavMQMIavF/V09Pfi+SMtjy3wQVlA30g6/yZzM9TGfCKeo dS2As+89FhUrMG58gzAzqhEFHLxs6X3XlGvvGS5Lb2ygqT2EwhmaQbQdN0iKufTtLKl1 yxov33UPeYX7uryd6WSgsmRv7G7qZg1iXy86f2iYKMIcTA36C9ooyF/GMJqwUUbxuX/z x79ursCe2w2hGXJu5HEWerelPqplnVvkveCFqNVNQ0Ck7wlGy1Y5pyQ8dmXn5V5kBDoW FpSw== X-Forwarded-Encrypted: i=1; AJvYcCVuTpV2PT1/LR0xfPAJDTqGjCqsnn7KiDtMP3A33tA/ROn3uVMk8Kw1CXbEAQrGJONOAIepV+5bWlyS@lists.linux.dev X-Gm-Message-State: AOJu0YzEg1f3XhzfCHD0sEUUu7rajtmJ1lE1hwVs/MFgWhysaGDsGYU5 Wg+dRj0jk0pKDAs2l3oLmF30V8y2DbMGpzHpo4TTa6kUoyD1ot6wqFn4gn8z/bl9dZ2veZfZuxj H5hM7Zg== X-Google-Smtp-Source: AGHT+IFGhHo2Di0bU/Eld4A49PARSXoqPeeyu/ySpV1D9gJIOdjNn1G+WqeVqdSQrN5R+YSZ+ehbNpIGVJQ= X-Received: from plow8.prod.google.com ([2002:a17:903:1b08:b0:267:cd3d:3446]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f54c:b0:295:134:9ae5 with SMTP id d9443c01a7336-29519b9f27cmr11657375ad.24.1761855006488; Thu, 30 Oct 2025 13:10:06 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:26 -0700 In-Reply-To: <20251030200951.3402865-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251030200951.3402865-1-seanjc@google.com> X-Mailer: git-send-email 2.51.1.930.gacf6e81ea2-goog Message-ID: <20251030200951.3402865-4-seanjc@google.com> Subject: [PATCH v4 03/28] KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings From: Sean Christopherson To: Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Madhavan Srinivasan , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Sean Christopherson , Paolo Bonzini , "Kirill A. Shutemov" Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, Ira Weiny , Kai Huang , Binbin Wu , Michael Roth , Yan Zhao , Vishal Annapurve , Rick Edgecombe , Ackerley Tng Content-Type: text/plain; charset="UTF-8" Drop TDX's sanity check that a mirror EPT mapping isn't zapped between creating said mapping and doing TDH.MEM.PAGE.ADD, as the check is simultaneously superfluous and incomplete. Per commit 2608f1057601 ("KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU"), the justification for introducing kvm_tdp_mmu_gpa_is_mapped() was to check that the target gfn was pre-populated, with a link that points to this snippet: : > One small question: : > : > What if the memory region passed to KVM_TDX_INIT_MEM_REGION hasn't been pre- : > populated? If we want to make KVM_TDX_INIT_MEM_REGION work with these regions, : > then we still need to do the real map. Or we can make KVM_TDX_INIT_MEM_REGION : > return error when it finds the region hasn't been pre-populated? : : Return an error. I don't love the idea of bleeding so many TDX details into : userspace, but I'm pretty sure that ship sailed a long, long time ago. But that justification makes little sense for the final code, as the check on nr_premapped after TDH.MEM.PAGE.ADD will detect and return an error if KVM attempted to zap a S-EPT entry (tdx_sept_zap_private_spte() will fail on TDH.MEM.RANGE.BLOCK due lack of a valid S-EPT entry). And as evidenced by the "is mapped?" code being guarded with CONFIG_KVM_PROVE_MMU=y, KVM is NOT relying on the check for general correctness. The sanity check is also incomplete in the sense that mmu_lock is dropped between the check and TDH.MEM.PAGE.ADD, i.e. will only detect KVM bugs that zap SPTEs in a very specific window (note, this also applies to the check on nr_premapped). Removing the sanity check will allow removing kvm_tdp_mmu_gpa_is_mapped(), which has no business being exposed to vendor code, and more importantly will pave the way for eliminating the "pre-map" approach entirely in favor of doing TDH.MEM.PAGE.ADD under mmu_lock. Reviewed-by: Ira Weiny Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 326db9b9c567..4c3014befe9f 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3181,20 +3181,6 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, if (ret < 0) goto out; - /* - * The private mem cannot be zapped after kvm_tdp_map_page() - * because all paths are covered by slots_lock and the - * filemap invalidate lock. Check that they are indeed enough. - */ - if (IS_ENABLED(CONFIG_KVM_PROVE_MMU)) { - scoped_guard(read_lock, &kvm->mmu_lock) { - if (KVM_BUG_ON(!kvm_tdp_mmu_gpa_is_mapped(vcpu, gpa), kvm)) { - ret = -EIO; - goto out; - } - } - } - ret = 0; err = tdh_mem_page_add(&kvm_tdx->td, gpa, pfn_to_page(pfn), src_page, &entry, &level_state); -- 2.51.1.930.gacf6e81ea2-goog