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 D593D37F31A; Thu, 20 Aug 2026 15:06:24 +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=1787238386; cv=none; b=ExkWtu0qaEoXW0bTVOgI83cxSikXkSB2CyY4xGH327A8i0Kso9VqCYGX7I46nrTWfUa6iyz16e16m9k2rHydMoNbRHaUFlts6IL0GvJm+4bh+Qzqumr0Y2BdtV25jWRVC1EhH1VEX3IuTLxgs8tNONx0LBZAhRO2SyL+Itdbaac= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787238386; c=relaxed/simple; bh=UyDYm8w5MFxsxwKAMa9U+W5CrpEK1iA9ZEngwe2xHvk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eKLgbEz6dQCtHw7KiT3l73C+mnq6nW0dpWQFoHCEH5Y3zkOGIIe/oG3Rl7zlgiJAQyVog0WLTg+J/B/0of3+BgJBBktDh0ZSA0jQwV02xAdFfm9ocWGGh1+pjSiOOgdQubLY81EcCl1MBWLCpkPfrNxwCq076kATnGgJnHGWkkw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JYUcsuv3; 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="JYUcsuv3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B4961F000E9; Thu, 20 Aug 2026 15:06:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787238384; bh=yJgre99bHj8z9ohtKKzcmJ6vfPGHxsjPab1aLlsLa0M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JYUcsuv3z10NiJQy+3Pr7vn4morGK9rUu/9oKwD499QtYvN0n3vkKEeDTZ5XuYy36 nx9+fIw2extS3yaJDgKvCIoqmhaf/Pij/TvdtbQiMjBZ2yUJl6jzaLwcuAx+Ogt6cS e86TU0KNknjNuCJevbanPL+igT5QLV4ni8wH1PX8= 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 7.1 102/228] s390/vfio_ccw: Selectively expand io_mutex Date: Thu, 20 Aug 2026 16:54:04 +0200 Message-ID: <20260820145247.748003438@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145244.450574346@linuxfoundation.org> References: <20260820145244.450574346@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-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