From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) (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 820AC41DDF4 for ; Tue, 18 Aug 2026 08:12:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787040781; cv=none; b=Mfhi+/MtLgUbolctiEk34g+B4adcPFKJ1Q0YHw7jVTk5FSS5i4gXQw+Wg2iNmumvlZEZof0PDv0D2nwbiXflIApR/xm2IpG0vIaCfAoxa1Bd5uLfqTkspA8yvHIqlzzTSfKc0f/raOKTGxMeiiT6vnqctiejD8B6o8PSUPhuYrs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787040781; c=relaxed/simple; bh=7i6cqBtbFkQctrI98iz0J10uujeLpSmIIWcG5kUAid8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Kk1/ttjTFFzdeg0bKRMuGQhDwChJtHcpCEJoPyLbF3/HkHvaVRUjfMz8r5G9E9iMjFDmDtkchuWcjccFC1svccVL+PY5+imUKwNgkpLF4VVRm0zYjeDjNSHasDiJu4Kyemaip2e8zKaPXhe3Xg4MPILO+mB/VOzlbabG9C+VGjY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--ackerleytng.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=SxBNQ2WZ; arc=none smtp.client-ip=209.85.210.197 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--ackerleytng.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SxBNQ2WZ" Received: by mail-pf1-f197.google.com with SMTP id d2e1a72fcca58-8485b7e18b4so7129406b3a.1 for ; Tue, 18 Aug 2026 01:12:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787040778; x=1787645578; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=k3ULsNgYxwRhZwue5bCy+g9EswRkhCGynb1/tmXwwp8=; b=SxBNQ2WZdi+yx7i7T7w80XIWfig5JXAq1IWse2xb9wjL5jzs7Y/0BbaEBuDOyNskvY sTqgSq9vfnOQtvByY+mBoyGH8Ta0kDCEK9zQh1V8T6xP00emtVokHkndvObiiIsEJlHh o+rhVAIKMWL7nkZGFtpCdOMhLvjHz/vYCwRaSRTke0S8AlyKuFS7pVuQhj0sGyDD57K8 5goXyDd+eT0fiVNLY6SWfUQ0AAeE/f+WZMsjOAe1+6TISUBLM/nYehISFSK07bpI8FjO VFp8VHhlzw+rwyC4EamFiEsWMKYrlG3o121nxmDgUWl8CueU9oPrYdVLd0uroMnuHlfc 1Obg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787040778; x=1787645578; h=content-type: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:content-type; bh=k3ULsNgYxwRhZwue5bCy+g9EswRkhCGynb1/tmXwwp8=; b=KQEkn8XNwJ2brVMZ3vHHy3fBScCAqm9NdBayXHMQ0PkeKv1POraWNTqUpk9Z7ZnLVt oMkrwOsAs1OIz4uLAxDBkDgi9zNlbDWPiLDgcntz2b20Ss6rAdDNz6DeAf8RRErxS1sz mNe6FVbJgAn3iOqp+7MzoIk3S3iPiREcY4fE460i3nTywg8DjWXTsal6g2RTIe47gSU2 nZd1r7rI5hr649GkeHhrieCwHyorOupEQEAJVVT56/RAEV5oqXjyaoxWSKr0upgKeGdW /eWQuQU1N05Ao/T280LrbQ1OACGX2EVuFbRbv/rK7p5V4/t4jE2YXN2J2n4/k+fMHuV4 Ep1Q== X-Forwarded-Encrypted: i=1; AHgh+RoVhuVqjWBmZ4YzkvKpZ7nsSDOTyBNKiQ123XKcAm+FBK+MM0oIJ8FG+/MyTt2tQC7gwj2w1SZUEJT/ozk=@vger.kernel.org X-Gm-Message-State: AOJu0YyUbH9YkQ8XnTAvLigQ1O59fZkca3LqbVAs9vKMe33/X2OjGHUY hJUvLTaqFpeBQ/IJk4iNBnGjzq8TZAM1Ey5Jfq1LxS1WIZ9Vcxvtb9oe1FoqV8qGmiZQdgucN95 M5VwTRBIZ1f6QXnptOMqUX0tBcw== X-Received: from pglf19.prod.google.com ([2002:a63:1013:0:b0:c96:da8a:c09c]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:10a:b0:3cb:853e:850e with SMTP id adf61e73a8af0-3cc71b7acbamr41629166637.13.1787040777693; Tue, 18 Aug 2026 01:12:57 -0700 (PDT) Date: Tue, 18 Aug 2026 08:12:36 +0000 In-Reply-To: <20260818-gmem-no-return-page-v1-0-4f8d939efdbc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260818-gmem-no-return-page-v1-0-4f8d939efdbc@google.com> X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Developer-Signature: v=1; a=ed25519-sha256; t=1787040773; l=1697; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=7i6cqBtbFkQctrI98iz0J10uujeLpSmIIWcG5kUAid8=; b=ekVPncMmVUriS84Zt3+p8nRYXWSGEYGwwUVXJK5NXlHtz70OGF8spprSioZ5xfncCfU5EKAue 7ocjFnw2d/JCgGzlgbUnq1q4Jp4Sgvc0ggqydJcjSIEBFCCyy17BUEN X-Mailer: b4 0.16.0 Message-ID: <20260818-gmem-no-return-page-v1-2-4f8d939efdbc@google.com> Subject: [PATCH 2/4] KVM: SEV: Drop page refcount early during RMP fault handling From: Ackerley Tng To: Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Ashish Kalra , Michael Roth , Brijesh Singh , Marc Zyngier , Oliver Upton , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , David Hildenbrand , Fuad Tabba , Yan Zhao , "Edgecombe, Rick P" , Vishal Annapurve Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Ackerley Tng Content-Type: text/plain; charset="utf-8" When handling an RMP fault, KVM retrieves the PFN for a private GPA from guest_memfd. The page reference taken during PFN lookup is not needed for the remainder of the handler, as checking the RMP entry, splitting the 2MB page via PSMASH, and zapping shadow page tables only operate on PFNs. Drop the page reference immediately after retrieving the PFN instead of holding it across the entire handler. A later patch will follow up with completely not returning refcounted pages from kvm_gmem_get_pfn(). No functional change intended. Signed-off-by: Ackerley Tng --- arch/x86/kvm/svm/sev.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index b2738362a928b..19c31fa944e34 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -5036,12 +5036,13 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code) gpa); return; } + kvm_release_page_unused(page); ret = snp_lookup_rmpentry(pfn, &assigned, &rmp_level); if (ret || !assigned) { pr_warn_ratelimited("SEV: Unexpected RMP fault, no assigned RMP entry found for GPA 0x%llx PFN 0x%llx error %d\n", gpa, pfn, ret); - goto out_no_trace; + return; } /* @@ -5088,8 +5089,6 @@ void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code) kvm_zap_gfn_range(kvm, gfn, gfn + PTRS_PER_PMD); out: trace_kvm_rmp_fault(vcpu, gpa, pfn, error_code, rmp_level, ret); -out_no_trace: - kvm_release_page_unused(page); } static bool is_pfn_range_shared(kvm_pfn_t start, kvm_pfn_t end) -- 2.55.0.699.gb54405d56f-goog