From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 9597A524F for ; Wed, 27 Aug 2025 00:05:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756253128; cv=none; b=aM8Bc6nYXXfPtFkj2VpDhVQGXdftdfvW5rAdSrEepaHWYecY+/nKKeLD9Qoup6bwOF7U9YGaVoP00fTXn/i+ubr1XQBCcgUpTIVAfkPE4afJLQhaiQKMoKjL1DDqvGVIrcp2dwhOJo3DTjzAfLLZ9zoNzoGfUJuqAfpB+Riveck= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756253128; c=relaxed/simple; bh=BYrpGObWdcKQBFBTHXHA+hrFfJH7FFHHmouCdbQhKuI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Z98TWtn8LW2Qs/O6helb53B40hoWTXrHtemuliVPsRlyGMu+DL8UkuJwgAygDWPyeJGNkgK7HaNMvSCRB81rf3FIFeXazdYl8izR82knyM97BXG4DIEUZd0CQb6uG5U/9Vo44ndPjEjz06vjU/HXC3RqaxSiBlSdOo0DA6SIb9U= 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=jGyojEsT; arc=none smtp.client-ip=209.85.216.74 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="jGyojEsT" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-324e4c3af5fso6258188a91.3 for ; Tue, 26 Aug 2025 17:05:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1756253126; x=1756857926; darn=vger.kernel.org; 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=s1TG4lPviW9zkkUbrVAE+VToTbwmtvD/jmWrMLbsJcE=; b=jGyojEsT4ct+XdN2AQet9P+2+mGXhZRRCRdydxtZwyXB60FKS+0hlk4KUtiiA62Y41 814sSBNWgLob50pQ4IfEfo/OCQy+UCcTZnIXNwA895PUTMbKECTIEJ6flQXvXok1OLCI RioIjZ6vGtEv32GbiZ8ZIwzwFePa5rhcGFLFfvF/pybMpSkEjVaZxs/JYg7UiEyJDN5F zs2Ed/2GoNnV2VkgvM5iooKOcOGNwKaIEDp4wD1KCMVx0yXgHSqmX/DQ70V05oVHV59M n4iz0a2n0glh0BU34QNeRja9f5Phy7kCDganOGrRWJBpWVPBXWwsu7nqF81YMgfkdwcr uNrg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756253126; x=1756857926; 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=s1TG4lPviW9zkkUbrVAE+VToTbwmtvD/jmWrMLbsJcE=; b=SZJYx+PT45gcYwc4F/EY5RP7P1S57bJOE8QMv3MGGlhIfjbIL0RZsNeXTVF7hCCQtL 8Hpw7YM8CxNNQRiFP86rXgmD5fdDkIzVi+HziXlFA/wMFJofOMRIzDDxOCEGuNJF6cUN iyTnnRj6ntcu/N7tVWZumnX98k/2TYxC0wvq6/Slfgf7dzmJ6vuARDeE7XQMmrnIYMDn G+2X7IVVf5cdqlRJsjQTUV4M3juVQs7qYAtrzguOS1N1/N5aGrSUxalaOu0G14v9samy lZYlXeqIpbcAMGf5iJKoQh8A1hKIHByGvHeGUpMZptR8JWeMcIrQ1MZjP2CpK6uO+BP+ /veg== X-Gm-Message-State: AOJu0YxR5s+LrH3I0aaVl1WclSErEMXdYJbPQmjju7GqkgZnpDKO2hZL 5YrJmsg6wZ76B6Blce2hulxCg2SDmXRijSjcilvOKZz7t2eVduCN8DmLwMV3GFeh+tyqjZWf9Wl OcCpVGg== X-Google-Smtp-Source: AGHT+IHMYfnsineRSbdna+fy5FAeFnMFw6K03y0LLQ596CpMf66ldbok0nFnHZEXgnhOL9BnTiJGl1S20gs= X-Received: from pjae9.prod.google.com ([2002:a17:90a:1189:b0:327:5941:b2fd]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4c85:b0:323:28ac:4594 with SMTP id 98e67ed59e1d1-32515e2e438mr18787121a91.5.1756253125797; Tue, 26 Aug 2025 17:05:25 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 26 Aug 2025 17:05:11 -0700 In-Reply-To: <20250827000522.4022426-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250827000522.4022426-1-seanjc@google.com> X-Mailer: git-send-email 2.51.0.268.g9569e192d0-goog Message-ID: <20250827000522.4022426-2-seanjc@google.com> Subject: [RFC PATCH 01/12] KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Roth , Yan Zhao , Ira Weiny , Vishal Annapurve , Rick Edgecombe Content-Type: text/plain; charset="UTF-8" Drop TDX's sanity check that an S-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 simply doing TDH.MEM.PAGE.ADD without a paranoid sanity check will return an error if the S-EPT mapping is invalid (as evidenced by the code being guarded with CONFIG_KVM_PROVE_MMU=y). 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. Removing the sanity check will allow removing kvm_tdp_mmu_gpa_is_mapped(), which has no business being exposed to vendor code. 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 66744f5768c8..a6155f76cc6a 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3175,20 +3175,6 @@ 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); -- 2.51.0.268.g9569e192d0-goog