From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Sasha Levin <sashal@kernel.org>,
virtualization@lists.linux-foundation.org
Subject: [PATCH AUTOSEL 5.10 37/37] virtio: fix up virtio_disable_cb
Date: Sat, 10 Jul 2021 19:50:15 -0400 [thread overview]
Message-ID: <20210710235016.3221124-37-sashal@kernel.org> (raw)
In-Reply-To: <20210710235016.3221124-1-sashal@kernel.org>
From: "Michael S. Tsirkin" <mst@redhat.com>
[ Upstream commit 8d622d21d24803408b256d96463eac4574dcf067 ]
virtio_disable_cb is currently a nop for split ring with event index.
This is because it used to be always called from a callback when we know
device won't trigger more events until we update the index. However,
now that we run with interrupts enabled a lot we also poll without a
callback so that is different: disabling callbacks will help reduce the
number of spurious interrupts.
Further, if using event index with a packed ring, and if being called
from a callback, we actually do disable interrupts which is unnecessary.
Fix both issues by tracking whenever we get a callback. If that is
the case disabling interrupts with event index can be a nop.
If not the case disable interrupts. Note: with a split ring
there's no explicit "no interrupts" value. For now we write
a fixed value so our chance of triggering an interupt
is 1/ring size. It's probably better to write something
related to the last used index there to reduce the chance
even further. For now I'm keeping it simple.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/virtio/virtio_ring.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 71e16b53e9c1..88f0b16b11b8 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -113,6 +113,9 @@ struct vring_virtqueue {
/* Last used index we've seen. */
u16 last_used_idx;
+ /* Hint for event idx: already triggered no need to disable. */
+ bool event_triggered;
+
union {
/* Available for split ring */
struct {
@@ -739,7 +742,10 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
- if (!vq->event)
+ if (vq->event)
+ /* TODO: this is a hack. Figure out a cleaner value to write. */
+ vring_used_event(&vq->split.vring) = 0x0;
+ else
vq->split.vring.avail->flags =
cpu_to_virtio16(_vq->vdev,
vq->split.avail_flags_shadow);
@@ -1605,6 +1611,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
vq->weak_barriers = weak_barriers;
vq->broken = false;
vq->last_used_idx = 0;
+ vq->event_triggered = false;
vq->num_added = 0;
vq->packed_ring = true;
vq->use_dma_api = vring_use_dma_api(vdev);
@@ -1919,6 +1926,12 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
+ /* If device triggered an event already it won't trigger one again:
+ * no need to disable.
+ */
+ if (vq->event_triggered)
+ return;
+
if (vq->packed_ring)
virtqueue_disable_cb_packed(_vq);
else
@@ -1942,6 +1955,9 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
+ if (vq->event_triggered)
+ vq->event_triggered = false;
+
return vq->packed_ring ? virtqueue_enable_cb_prepare_packed(_vq) :
virtqueue_enable_cb_prepare_split(_vq);
}
@@ -2005,6 +2021,9 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
+ if (vq->event_triggered)
+ vq->event_triggered = false;
+
return vq->packed_ring ? virtqueue_enable_cb_delayed_packed(_vq) :
virtqueue_enable_cb_delayed_split(_vq);
}
@@ -2044,6 +2063,10 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
if (unlikely(vq->broken))
return IRQ_HANDLED;
+ /* Just a hint for performance: so it's ok that this can be racy! */
+ if (vq->event)
+ vq->event_triggered = true;
+
pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
if (vq->vq.callback)
vq->vq.callback(&vq->vq);
@@ -2083,6 +2106,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
vq->weak_barriers = weak_barriers;
vq->broken = false;
vq->last_used_idx = 0;
+ vq->event_triggered = false;
vq->num_added = 0;
vq->use_dma_api = vring_use_dma_api(vdev);
#ifdef DEBUG
--
2.30.2
prev parent reply other threads:[~2021-07-10 23:52 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-10 23:49 [PATCH AUTOSEL 5.10 01/37] power: supply: sc27xx: Add missing MODULE_DEVICE_TABLE Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 02/37] power: supply: sc2731_charger: " Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 03/37] f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 04/37] pwm: spear: Don't modify HW state in .remove callback Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 05/37] PCI: ftpci100: Rename macro name collision Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 06/37] power: supply: ab8500: Avoid NULL pointers Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 07/37] PCI: hv: Fix a race condition when removing the device Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 08/37] power: supply: max17042: Do not enforce (incorrect) interrupt trigger type Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 09/37] power: reset: gpio-poweroff: add missing MODULE_DEVICE_TABLE Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 10/37] ARM: 9087/1: kprobes: test-thumb: fix for LLVM_IAS=1 Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 11/37] PCI/P2PDMA: Avoid pci_get_slot(), which may sleep Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 12/37] NFSv4: Fix delegation return in cases where we have to retry Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 13/37] PCI: pciehp: Ignore Link Down/Up caused by DPC Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 14/37] watchdog: Fix possible use-after-free in wdt_startup() Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 15/37] watchdog: sc520_wdt: Fix possible use-after-free in wdt_turnoff() Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 16/37] watchdog: Fix possible use-after-free by calling del_timer_sync() Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 17/37] watchdog: imx_sc_wdt: fix pretimeout Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 18/37] watchdog: iTCO_wdt: Account for rebooting on second timeout Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 19/37] x86/fpu: Return proper error codes from user access functions Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 20/37] remoteproc: core: Fix cdev remove and rproc del Sasha Levin
2021-07-10 23:49 ` [PATCH AUTOSEL 5.10 21/37] PCI: tegra: Add missing MODULE_DEVICE_TABLE Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 22/37] orangefs: fix orangefs df output Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 23/37] ceph: remove bogus checks and WARN_ONs from ceph_set_page_dirty Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 24/37] drm/gma500: Add the missed drm_gem_object_put() in psb_user_framebuffer_create() Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 25/37] NFS: nfs_find_open_context() may only select open files Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 26/37] power: supply: charger-manager: add missing MODULE_DEVICE_TABLE Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 27/37] power: supply: ab8500: " Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 28/37] drm/amdkfd: fix sysfs kobj leak Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 29/37] pwm: img: Fix PM reference leak in img_pwm_enable() Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 30/37] pwm: tegra: Don't modify HW state in .remove callback Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 31/37] ACPI: AMBA: Fix resource name in /proc/iomem Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 32/37] ACPI: video: Add quirk for the Dell Vostro 3350 Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 33/37] PCI: rockchip: Register IRQ handlers after device and data are ready Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 34/37] virtio-blk: Fix memory leak among suspend/resume procedure Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 35/37] virtio_net: Fix error handling in virtnet_restore() Sasha Levin
2021-07-10 23:50 ` [PATCH AUTOSEL 5.10 36/37] virtio_console: Assure used length from device is limited Sasha Levin
2021-07-10 23:50 ` Sasha Levin [this message]
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