From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C0183378826; Thu, 20 Aug 2026 15:15:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787238916; cv=none; b=dbrjvSdseIX6i6fqyJy6F7r9Lz+VIZMOEDpTNVP/hQrDgmK82qEOXe915tqrTqIjcnRLW97QNLE+TM2VtCf/Zd1SAsIM+TfU92dok7QUAmzWh/RJOcMrMqTr4WJ+H2i6ry6EKoXFU0pDYE0XMTRb9sgRQZ6zxbX2BFHCOsqZGMA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787238916; c=relaxed/simple; bh=sw+SZtypDel9LyFntV7aNCzzc0hkz32UY/SaRDM2RPg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eTzqEOXxj+Ae6Hk2I23cl2IGEWEPS1pTtXXcqBdFfkzSiAu0d6hf6DHtNLIn4iAMj42yqFYJpEav5Jw/yawVExqN7iV3eIDqt2W1fOot6C5AwVwn579Bf9lCfko7HxpUGKrrowQ2/NzWucKS8N6Fx9BokWdKWcGjhrsNf8www70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NaIs4bS9; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="NaIs4bS9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 257DC1F000E9; Thu, 20 Aug 2026 15:15:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787238914; bh=PiX6rQPLGZnR2AuTj70UjhJqPYSsWm/bhVkNv6s8gsk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NaIs4bS9ICA5UThQb2T1py10fXI+d6g3Kd2AeSPj615iNZQNlJDJaynbEvKuZ7fje 5+dRSP8Ao0m7hHA9hGv+n7R8GOLAxr+c/IUIRMCeRKFGcRMy8Sj0Iv3rI7zgkN1Ol+ h3tNeOs0FVVoubbAE9HEBJB3lUw/wOBIyq4XSnFo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Farman , Matthew Rosato , Christian Borntraeger Subject: [PATCH 6.18 086/217] s390/vfio_ccw: Selectively expand io_mutex Date: Thu, 20 Aug 2026 16:54:14 +0200 Message-ID: <20260820145240.221294178@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145237.531699751@linuxfoundation.org> References: <20260820145237.531699751@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Farman commit 34f4feff3e90bd09308fad0974e97113b23b812a upstream. The io_mutex was defined to serialize the io_regions, but then has also sort of been associated with the I/O themselves because of the close relationship they share. With the handful of races that are possible, the choices are either to: A) expand the scope of io_mutex to close these remaining windows, or B) reduce the scope of io_mutex to just io_region, and introduce a new lock mechanism for the remaining I/O resources This patch implements A, since B brings with it a lot more interactions that would need to be tracked and kept in a correct hierarchy. It also takes advantage of the workqueue element for cp_free() that now gets called out of fsm_notoper(), which could be invoked out of an interrupt context and thus cannot acquire a mutex itself. Fixes: 4f76617378ee ("vfio-ccw: protect the I/O region") Cc: stable@vger.kernel.org Signed-off-by: Eric Farman Reviewed-by: Matthew Rosato Signed-off-by: Christian Borntraeger Signed-off-by: Greg Kroah-Hartman --- drivers/s390/cio/vfio_ccw_chp.c | 2 +- drivers/s390/cio/vfio_ccw_cp.c | 8 +++++++- drivers/s390/cio/vfio_ccw_drv.c | 6 ++++-- drivers/s390/cio/vfio_ccw_fsm.c | 5 +++++ drivers/s390/cio/vfio_ccw_private.h | 3 ++- 5 files changed, 19 insertions(+), 5 deletions(-) --- a/drivers/s390/cio/vfio_ccw_chp.c +++ b/drivers/s390/cio/vfio_ccw_chp.c @@ -98,13 +98,13 @@ static ssize_t vfio_ccw_crw_region_read( if (pos + count > sizeof(*region)) return -EINVAL; + mutex_lock(&private->io_mutex); crw = list_first_entry_or_null(&private->crw, struct vfio_ccw_crw, next); if (crw) list_del(&crw->next); - mutex_lock(&private->io_mutex); if (i >= private->num_regions) { ret = -EINVAL; goto out; --- a/drivers/s390/cio/vfio_ccw_cp.c +++ b/drivers/s390/cio/vfio_ccw_cp.c @@ -976,17 +976,23 @@ void cp_update_scsw(struct channel_progr */ bool cp_iova_pinned(struct channel_program *cp, u64 iova, u64 length) { + struct vfio_ccw_private *private = + container_of(cp, struct vfio_ccw_private, cp); struct ccwchain *chain; int i; if (!cp->initialized) return false; + mutex_lock(&private->io_mutex); list_for_each_entry(chain, &cp->ccwchain_list, next) { for (i = 0; i < chain->ch_len; i++) - if (page_array_iova_pinned(&chain->ch_pa[i], iova, length)) + if (page_array_iova_pinned(&chain->ch_pa[i], iova, length)) { + mutex_unlock(&private->io_mutex); return true; + } } + mutex_unlock(&private->io_mutex); return false; } --- a/drivers/s390/cio/vfio_ccw_drv.c +++ b/drivers/s390/cio/vfio_ccw_drv.c @@ -91,6 +91,7 @@ void vfio_ccw_sch_io_todo(struct work_st is_final = !(scsw_actl(&irb->scsw) & (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT)); + mutex_lock(&private->io_mutex); if (scsw_is_solicited(&irb->scsw)) { cp_update_scsw(&private->cp, &irb->scsw); if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) { @@ -98,9 +99,7 @@ void vfio_ccw_sch_io_todo(struct work_st cp_is_finished = true; } } - mutex_lock(&private->io_mutex); memcpy(private->io_region->irb_area, irb, sizeof(*irb)); - mutex_unlock(&private->io_mutex); /* * Reset to IDLE only if processing of a channel program @@ -110,6 +109,7 @@ void vfio_ccw_sch_io_todo(struct work_st */ if (cp_is_finished) private->state = VFIO_CCW_STATE_IDLE; + mutex_unlock(&private->io_mutex); if (private->io_trigger) eventfd_signal(private->io_trigger); @@ -131,7 +131,9 @@ void vfio_ccw_notoper_todo(struct work_s private = container_of(work, struct vfio_ccw_private, notoper_work); + mutex_lock(&private->io_mutex); cp_free(&private->cp); + mutex_unlock(&private->io_mutex); } /* --- a/drivers/s390/cio/vfio_ccw_fsm.c +++ b/drivers/s390/cio/vfio_ccw_fsm.c @@ -170,6 +170,7 @@ static void fsm_notoper(struct vfio_ccw_ css_sched_sch_todo(sch, SCH_TODO_UNREG); private->state = VFIO_CCW_STATE_NOT_OPER; + /* This routine could be called from IRQ context, so defer */ queue_work(vfio_ccw_work_q, &private->notoper_work); } @@ -409,7 +410,11 @@ static void fsm_close(struct vfio_ccw_pr private->state = VFIO_CCW_STATE_STANDBY; spin_unlock_irq(&sch->lock); + + mutex_lock(&private->io_mutex); cp_free(&private->cp); + mutex_unlock(&private->io_mutex); + return; err_unlock: --- a/drivers/s390/cio/vfio_ccw_private.h +++ b/drivers/s390/cio/vfio_ccw_private.h @@ -88,7 +88,8 @@ struct vfio_ccw_parent { * @state: internal state of the device * @completion: synchronization helper of the I/O completion * @io_region: MMIO region to input/output I/O arguments/results - * @io_mutex: protect against concurrent update of I/O regions + * @io_mutex: protect against concurrent update of I/O resources + * and @cp lifecycle * @region: additional regions for other subchannel operations * @cmd_region: MMIO region for asynchronous I/O commands other than START * @schib_region: MMIO region for SCHIB information