From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (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 BFF612264AB for ; Tue, 22 Sep 2026 00:13:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790036016; cv=none; b=Ti/WjEhwNlXEuCylDmup2HbkWlRl7aOjt668MMhnv/wWJyUHXIaNmJBRP4ZgnBmMVOYpTlM3HPs3DX8XmT+MDaRaPlS6MsH5n9RG7vXRlGToXipUZDGBh33DvQFnY3TX+ZBRtOJcWbGar74jI7xdsOZa+Cx2CK6Ql6AYcUo37w4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790036016; c=relaxed/simple; bh=jpQTZOsq9Y2zE31QAXD+PcxDvJuwfkohXQ2UD5qRwsc=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=XrROll5OKi0uIoaXcht38hJV3W+o+1CPPJ6uCYY6pVfii3lw2+2HglOrxM2UqWNgMNuo3drC1+gnrDmLLCHT3/XpF8uQGOlAJMul0VL2cRUhgMWsektJ5McrGLyzNLual8/ykUgwawX4/H7TGrAz4rADTUlh4pJJa3mu2l+2bYE= 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=mLwW3rwa; arc=none smtp.client-ip=209.85.214.199 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="mLwW3rwa" Received: by mail-pl1-f199.google.com with SMTP id d9443c01a7336-2db3b126c9fso46479965ad.0 for ; Mon, 21 Sep 2026 17:13:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790036014; x=1790640814; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date :reply-to:from:to:cc:subject:date:message-id:reply-to:content-type; bh=nsOiLRN27kcO3pnY9NI5vzYfVkfUxUTwKtW8W3jGLrI=; b=mLwW3rwaI9LymIg0BO5RCIYdCHOkzpInjzBUnoYHUFvFPF8ddVIUdxQj0gXXkMR+Ga tDIckD22JNCAtxmiGUqGI+H1dTizxoZgQcsw+pBySxgty3z+LWlXiwlQq/JXo8ayGZz8 iuAjOtqYnj1tirYFbbCU4e/sdtZv/0I2Czlr1EcPDfhPXz4AfVYWPEgPU2osGl9xWuFp zAWXbyASYt66MGAagudQ/Du1N8UPigxy8uQHmOMeYJhsJK5wyLpyVa2qHsIlJdFz24gp 5sXhQ5nxNW4w9+Lzp9DUFGb6MDqzLVloxjBwtyIUqLPcFYPpakYo4DPVzjMIeG4+71tb ufcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790036014; x=1790640814; h=content-type:cc:to:from:subject:message-id:mime-version:date :reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=nsOiLRN27kcO3pnY9NI5vzYfVkfUxUTwKtW8W3jGLrI=; b=IZ5nbpspACjnMoTzWLrHwsRgfUAiiyGOfXsvv8997B62yeYzBmDwR4XaDSDwTSV3RV chMwq8OUGqBzakP2Nr3bXVfR8Cp6VPNqKVYSLRjrt4VgsB+7jEnDXwrXEH2gnl51AZ1D dWyj98Llq6kgvzw2rYBzyC7fqjxr+oVZnqXq3ArpqmTfuldUNfZVGequK8d1ioHO4ayP CA6alco6Z0X5cf2Ir3VHI1V2PS38OZatiWs5TjRAO4YJHjygbCz7i3+0121RWsXR6cDi vxJZ3Nx7/sdIP/MmCz0wJYXpK/ifs0nUaQA2ensSVUM/clG+KbloQfG5CfkXct/5cnyU x+yQ== X-Forwarded-Encrypted: i=1; AKwUvBxGZNpfxFvmBJqvAUNhNTzY7D1bAToxzf3IEyENIl0SK5KZLfSBrp2tWuSbpayCmHE73Ls=@vger.kernel.org X-Gm-Message-State: AFuF++lWwskplvvrLnEZJWqHbdkDaloqAj8stZq1FGfttIBXA/1bMYD/ n99hDr2WAzbSXZKyJhYlG555uhl0KSJ87QVMDa0+3NFNp4yH09K+Djx7yDZp224gfWav/IPIX4x 5Aggf7w== X-Received: from plhz7.prod.google.com ([2002:a17:902:d9c7:b0:2df:4827:bcc7]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2983:b0:2dd:c100:4257 with SMTP id d9443c01a7336-2ddc1004551mr112666475ad.59.1790036013944; Mon, 21 Sep 2026 17:13:33 -0700 (PDT) Reply-To: Sean Christopherson Date: Mon, 21 Sep 2026 17:13:26 -0700 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <20260922001332.1121266-1-seanjc@google.com> Subject: [PATCH v5 0/6] KVM: guest_memfd: Fix binding bugs From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: David Hildenbrand , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Teodorescu , Dennis Tighe , Sashiko Bot , Ackerley Tng , Yan Zhao Content-Type: text/plain; charset="UTF-8" Sorry for the spam, I am hoping to get this applied before the in-place conversion series, and I really want to get that series applied this week. I finally gave up and split bind() into prepare()+commit(), and I actually like the end result. The only really ugly part is an extra #ifdef, but otherwise gifting the gmem file reference back to kvm_set_memory_region() avoids the TOCTOU issues and weird juggling that led me to initially reject a prepare()+commit() solution. Fix guest_memfd bugs related to binding to a memslot: - Handle errors when inserting into guest_memfd's binding xarray, e.g. to do the right thing on ENOMEM. - Bind a memslot only once the memslot is fully prepared (because it becomes reachable/visible once its inserted into gmem's bindings arraxy). v5: - Split bind() into prepare()+commit() so that the memslot has all the gmem goodies before calling kvm_arch_prepare_memory_region(). [Sashiko] v4: - https://lore.kernel.org/all/20260921210616.1024168-1-seanjc@google.com - Drop intermediate xar variable. [David, Ackerley] - Collect reviews. [David, Ackerley] - Restrict kvm_gmem_bind() to CREATE as calling kvm_arch_free_memslot() on FLAGS_ONLY changes is unsafe, and doing the right thing for dirty bitmaps is tricky for similar reasons. As a bonus, this eliminates the ugly almost-duplicate code that David pointed out. - Explain why KVM must deal with the unwind during bind(). [Ackerley] v3: - https://lore.kernel.org/all/20260904004342.3162959-1-seanjc@google.com - Nullify bindings on error before dropping invalidat lock. [Sashiko x3] v2: - https://lore.kernel.org/all/20260902182020.2615443-1-seanjc@google.com - Fix the binding-too-early bug. [Sashiko] - Explicitly zero the bindings entry on failure to ensure there are no partial entries. [Sashiko] v1: https://lore.kernel.org/all/20260826165154.766699-2-seanjc@google.com Sean Christopherson (6): KVM: guest_memfd: Gracefully handle xarray errors when binding a memslot KVM: Use goto to handle errors during memslot preparation KVM: Only bind memslot to guest_memfd instance for CREATE operations KVM: guest_memfd: Split bind() into prepare()+commit() phases KVM: guest_memfd: Establish memslot<=>guest_memfd bindings *after* memslot is ready KVM: guest_memfd: Drop superfluous WRITE_ONCE() when binding a memslot virt/kvm/guest_memfd.c | 68 ++++++++++++++++++++++++++---------------- virt/kvm/guest_memfd.h | 19 ++++++++---- virt/kvm/kvm_main.c | 65 ++++++++++++++++++++++++++-------------- 3 files changed, 99 insertions(+), 53 deletions(-) base-commit: 70c944caf570fda2d79baa71435589a8db39f048 -- 2.55.0.1082.g2b9226bbc0-goog