From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <tglx@linutronix.de>
Received: from galois.linutronix.de (Galois.linutronix.de. [193.142.43.55])
        by gmr-mx.google.com with ESMTPS id y187si140441wmd.1.2020.12.10.11.42.50
        for <linux-ntb@googlegroups.com>
        (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);
        Thu, 10 Dec 2020 11:42:50 -0800 (PST)
Message-Id: <20201210194045.360198201@linutronix.de>
Date: Thu, 10 Dec 2020 20:26:04 +0100
From: Thomas Gleixner <tglx@linutronix.de>
Subject: [patch 28/30] xen/events: Reduce irq_info::spurious_cnt storage size
References: <20201210192536.118432146@linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-transfer-encoding: 8-bit
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Marc Zyngier <maz@kernel.org>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Juergen Gross <jgross@suse.com>, Stefano Stabellini <sstabellini@kernel.org>, xen-devel@lists.xenproject.org, "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>, Helge Deller <deller@gmx.de>, afzal mohammed <afzal.mohd.ma@gmail.com>, linux-parisc@vger.kernel.org, Russell King <linux@armlinux.org.uk>, linux-arm-kernel@lists.infradead.org, Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Christian Borntraeger <borntraeger@de.ibm.com>, Heiko Carstens <hca@linux.ibm.com>, linux-s390@vger.kernel.org, Jani Nikula <jani.nikula@linux.intel.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>, Chris Wilson <chris@chris-wilson.co.uk>, Wambui Karuga <wambui.karugax@gmail.com>, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>, Linus Walleij <linus.walleij@linaro.org>, linux-gpio@vger.kernel.org, Lee Jones <lee.jones@linaro.org>, Jon Mason <jdmason@kudzu.us>, Dave Jiang <dave.jiang@intel.com>, Allen Hubbe <allenbh@gmail.com>, linux-ntb@googlegroups.com, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>, Rob Herring <robh@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>, Michal Simek <michal.simek@xilinx.com>, linux-pci@vger.kernel.org, Karthikeyan Mitran <m.karthikeyan@mobiveil.co.in>, Hou Zhiqiang <Zhiqiang.Hou@nxp.com>, Tariq Toukan <tariqt@nvidia.com>, "David S. Miller" <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org, linux-rdma@vger.kernel.org, Saeed Mahameed <saeedm@nvidia.com>, Leon Romanovsky <leon@kernel.org>
List-ID: <linux-ntb.googlegroups.com>

To prepare for interrupt spreading reduce the storage size of
irq_info::spurious_cnt to u8 so the required flag for the spreading logic
will not increase the storage size.

Protect the usage site against overruns.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xenproject.org
---
 drivers/xen/events/events_base.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -95,7 +95,7 @@ struct irq_info {
 	struct list_head list;
 	struct list_head eoi_list;
 	short refcnt;
-	short spurious_cnt;
+	u8 spurious_cnt;
 	enum xen_irq_type type; /* type */
 	unsigned irq;
 	evtchn_port_t evtchn;   /* event channel */
@@ -528,8 +528,10 @@ static void xen_irq_lateeoi_locked(struc
 		return;
 
 	if (spurious) {
-		if ((1 << info->spurious_cnt) < (HZ << 2))
-			info->spurious_cnt++;
+		if ((1 << info->spurious_cnt) < (HZ << 2)) {
+			if (info->spurious_cnt != 0xFF)
+				info->spurious_cnt++;
+		}
 		if (info->spurious_cnt > 1) {
 			delay = 1 << (info->spurious_cnt - 2);
 			if (delay > HZ)