From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-228.mta1.migadu.com [95.215.58.228]) (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 C5AA644C67F for ; Wed, 19 Aug 2026 10:28:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.228 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787135316; cv=none; b=cvVQ47Raj03vejuUTufflzXiQDZWk+R47qJyswJWfa52339Wy9fUW2BXeCCvQg7KUhUtjevMK+SAAa5a7yf/21idi7bq5/TtjDBEVtjg+JhBXd0K+9DddL/d4z9lvs7Xloe0mPZL7B+t1xvMM6Wy07BeTuqhtltGZkmhGyfF8Zg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787135316; c=relaxed/simple; bh=ND3FDfa/qCk5V+rP9yXVtcSn7EWp1L01qy+mI7z3Zkk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=tLDX5zjdX149+e3TUJ/CQ8inBJcueUcAh56XDKb47lW34aICpiD5sZaH0R2x+u+LmAge3cWhrvY78aTpUZ5H4zmhwDNCwui7tRgSeomMeUopV9pw2SXk3lTS4txc+yrhA/l/VkMJEHaqBM2Mvt8DVF6CBXt0gfMAspLSiOYpPfs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=OiKqPEq3; arc=none smtp.client-ip=95.215.58.228 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="OiKqPEq3" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=ND3FDfa/qCk5V+rP9yXVtcSn7EWp1L01qy+mI7z3Zkk=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1787135309; v=1; x=1787740109; b=OiKqPEq3KTu4gORRoIWR5xMLppn2wWk+G5qLoG7tMPbFJ+iLPGHpMb8vnfrdP8qfMihHZI9f EP9c1yYiQZ5VVHXGJQU7072aOW6j9jSUhzY5zgF3AFXJUVWZCe9/tMMnAefPIoRz6huSmSfRs2V 47ibg3ffvAEFyq89QJaNTb+I= X-Envelope-To: linux-kernel@vger.kernel.org Received: from claudy.lan (37.156.72.212) by smtp.migadu.com with ESMTPS id 3086ea0630f1674f; Wed, 19 Aug 2026 10:28:28 +0000 X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: Marc Zyngier , Oliver Upton Cc: Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Will Deacon , Sascha Bischoff , Sebastian Ene , Eric Auger , Fuad Tabba , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/4] KVM: arm64: vgic-its: Skip unreachable devices instead of failing the save Date: Wed, 19 Aug 2026 11:28:08 +0100 Message-Id: <20260819102809.310708-4-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260819102809.310708-1-fuad.tabba@linux.dev> References: <20260819102809.310708-1-fuad.tabba@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vgic_its_save_device_tables() aborts with -EINVAL when a device's entry falls outside the device table, which a guest can arrange on its own: an indirect table lets it clear an L1 entry's valid bit without touching GITS_BASER. That fails a save userspace should be able to issue reliably. Skip the device instead, and point the saved DTE chain past it, as commit ad1e686e2378d ("KVM: arm64: vgic-its: Point saved ITEs at the next valid entry") does for ITEs. compute_next_devid_offset() takes the next device off the list whether or not it was saved, so the predecessor would otherwise point at an entry the save never wrote. Restore follows that offset while it stays inside the table being scanned: within an L2 block, or anywhere in a flat table. Both need userspace to remove a memslot under the table, since dropping an L1 entry takes the whole block with it and scan_its_table() stops at the block boundary. Fixes: 57a9a117154c9 ("KVM: arm64: vgic-its: Device table save/restore") Suggested-by: Marc Zyngier Link: https://lore.kernel.org/all/86bjaz5s6v.wl-maz@kernel.org/ Signed-off-by: Fuad Tabba --- arch/arm64/kvm/vgic/vgic-its.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c index cc6ea5c3409ae..717fbd563fb01 100644 --- a/arch/arm64/kvm/vgic/vgic-its.c +++ b/arch/arm64/kvm/vgic/vgic-its.c @@ -2013,18 +2013,22 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev, return ret; } -static u32 compute_next_devid_offset(struct list_head *h, +static u32 compute_next_devid_offset(struct vgic_its *its, u64 baser, struct its_device *dev) { - struct its_device *next; - u32 next_offset; + struct its_device *next = dev; - if (list_is_last(&dev->dev_list, h)) - return 0; - next = list_next_entry(dev, dev_list); - next_offset = next->device_id - dev->device_id; + /* + * Point at the next device vgic_its_save_device_tables() saves. It + * sorts device_list first, so the subtraction cannot underflow. + */ + list_for_each_entry_continue(next, &its->device_list, dev_list) { + if (vgic_its_check_id(its, baser, next->device_id, NULL)) + return min_t(u32, next->device_id - dev->device_id, + VITS_DTE_MAX_DEVID_OFFSET); + } - return min_t(u32, next_offset, VITS_DTE_MAX_DEVID_OFFSET); + return 0; } static u32 compute_next_eventid_offset(struct list_head *h, struct its_ite *ite) @@ -2265,17 +2269,18 @@ static int vgic_its_restore_itt(struct vgic_its *its, struct its_device *dev) * vgic_its_save_dte - Save a device table entry at a given GPA * * @its: ITS handle + * @baser: GITS_BASER the caller is saving against * @dev: ITS device * @ptr: GPA */ -static int vgic_its_save_dte(struct vgic_its *its, struct its_device *dev, - gpa_t ptr) +static int vgic_its_save_dte(struct vgic_its *its, u64 baser, + struct its_device *dev, gpa_t ptr) { u64 val, itt_addr_field; u32 next_offset; itt_addr_field = dev->itt_addr >> 8; - next_offset = compute_next_devid_offset(&its->device_list, dev); + next_offset = compute_next_devid_offset(its, baser, dev); val = (1ULL << KVM_ITS_DTE_VALID_SHIFT | ((u64)next_offset << KVM_ITS_DTE_NEXT_SHIFT) | (itt_addr_field << KVM_ITS_DTE_ITTADDR_SHIFT) | @@ -2374,15 +2379,16 @@ static int vgic_its_save_device_tables(struct vgic_its *its) int ret; gpa_t eaddr; + /* Don't fail a save that userspace must be able to issue. */ if (!vgic_its_check_id(its, baser, dev->device_id, &eaddr)) - return -EINVAL; + continue; ret = vgic_its_save_itt(its, dev); if (ret) return ret; - ret = vgic_its_save_dte(its, dev, eaddr); + ret = vgic_its_save_dte(its, baser, dev, eaddr); if (ret) return ret; } -- 2.39.5