Re: [PATCH 1/2] iommu/vt-d: Don't queue_iova() if there is no flush queue
From: Lu Baolu
Date: Fri Jul 19 2019 - 05:27:33 EST
Hi,
On 7/17/19 5:38 AM, Dmitry Safonov wrote:
Intel VT-d driver was reworked to use common deferred flushing
implementation. Previously there was one global per-cpu flush queue,
afterwards - one per domain.
Before deferring a flush, the queue should be allocated and initialized.
Currently only domains with IOMMU_DOMAIN_DMA type initialize their flush
queue. It's probably worth to init it for static or unmanaged domains
too, but it may be arguable - I'm leaving it to iommu folks.
We will submit per-device dma ops soon. Then we don't need to call
intel_unmap() for the identity (static) domain. For unmanaged domains,
the map/unmap happen only during VM startup/shutdown, I am not sure
whether it's worth a flush queue.
This fix looks good to me anyway. We should always avoid deferring a
flush if there's no flush queue there.
Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Best regards,
Baolu
Prevent queuing an iova flush if the domain doesn't have a queue.
The defensive check seems to be worth to keep even if queue would be
initialized for all kinds of domains. And is easy backportable.
On 4.19.43 stable kernel it has a user-visible effect: previously for
devices in si domain there were crashes, on sata devices:
BUG: spinlock bad magic on CPU#6, swapper/0/1
lock: 0xffff88844f582008, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
CPU: 6 PID: 1 Comm: swapper/0 Not tainted 4.19.43 #1
Call Trace:
<IRQ>
dump_stack+0x61/0x7e
spin_bug+0x9d/0xa3
do_raw_spin_lock+0x22/0x8e
_raw_spin_lock_irqsave+0x32/0x3a
queue_iova+0x45/0x115
intel_unmap+0x107/0x113
intel_unmap_sg+0x6b/0x76
__ata_qc_complete+0x7f/0x103
ata_qc_complete+0x9b/0x26a
ata_qc_complete_multiple+0xd0/0xe3
ahci_handle_port_interrupt+0x3ee/0x48a
ahci_handle_port_intr+0x73/0xa9
ahci_single_level_irq_intr+0x40/0x60
__handle_irq_event_percpu+0x7f/0x19a
handle_irq_event_percpu+0x32/0x72
handle_irq_event+0x38/0x56
handle_edge_irq+0x102/0x121
handle_irq+0x147/0x15c
do_IRQ+0x66/0xf2
common_interrupt+0xf/0xf
RIP: 0010:__do_softirq+0x8c/0x2df
The same for usb devices that use ehci-pci:
BUG: spinlock bad magic on CPU#0, swapper/0/1
lock: 0xffff88844f402008, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.43 #4
Call Trace:
<IRQ>
dump_stack+0x61/0x7e
spin_bug+0x9d/0xa3
do_raw_spin_lock+0x22/0x8e
_raw_spin_lock_irqsave+0x32/0x3a
queue_iova+0x77/0x145
intel_unmap+0x107/0x113
intel_unmap_page+0xe/0x10
usb_hcd_unmap_urb_setup_for_dma+0x53/0x9d
usb_hcd_unmap_urb_for_dma+0x17/0x100
unmap_urb_for_dma+0x22/0x24
__usb_hcd_giveback_urb+0x51/0xc3
usb_giveback_urb_bh+0x97/0xde
tasklet_action_common.isra.4+0x5f/0xa1
tasklet_action+0x2d/0x30
__do_softirq+0x138/0x2df
irq_exit+0x7d/0x8b
smp_apic_timer_interrupt+0x10f/0x151
apic_timer_interrupt+0xf/0x20
</IRQ>
RIP: 0010:_raw_spin_unlock_irqrestore+0x17/0x39
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # 4.14+
Fixes: 13cf01744608 ("iommu/vt-d: Make use of iova deferred flushing")
Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
---
drivers/iommu/intel-iommu.c | 3 ++-
drivers/iommu/iova.c | 18 ++++++++++++++----
include/linux/iova.h | 6 ++++++
3 files changed, 22 insertions(+), 5 deletions(-)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index ac4172c02244..6d1510284d21 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3564,7 +3564,8 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)
freelist = domain_unmap(domain, start_pfn, last_pfn);
- if (intel_iommu_strict || (pdev && pdev->untrusted)) {
+ if (intel_iommu_strict || (pdev && pdev->untrusted) ||
+ !has_iova_flush_queue(&domain->iovad)) {
iommu_flush_iotlb_psi(iommu, domain, start_pfn,
nrpages, !freelist, 0);
/* free iova */
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index d499b2621239..8413ae54904a 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -54,9 +54,14 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
}
EXPORT_SYMBOL_GPL(init_iova_domain);
+bool has_iova_flush_queue(struct iova_domain *iovad)
+{
+ return !!iovad->fq;
+}
+
static void free_iova_flush_queue(struct iova_domain *iovad)
{
- if (!iovad->fq)
+ if (!has_iova_flush_queue(iovad))
return;
if (timer_pending(&iovad->fq_timer))
@@ -74,13 +79,14 @@ static void free_iova_flush_queue(struct iova_domain *iovad)
int init_iova_flush_queue(struct iova_domain *iovad,
iova_flush_cb flush_cb, iova_entry_dtor entry_dtor)
{
+ struct iova_fq __percpu *queue;
int cpu;
atomic64_set(&iovad->fq_flush_start_cnt, 0);
atomic64_set(&iovad->fq_flush_finish_cnt, 0);
- iovad->fq = alloc_percpu(struct iova_fq);
- if (!iovad->fq)
+ queue = alloc_percpu(struct iova_fq);
+ if (!queue)
return -ENOMEM;
iovad->flush_cb = flush_cb;
@@ -89,13 +95,17 @@ int init_iova_flush_queue(struct iova_domain *iovad,
for_each_possible_cpu(cpu) {
struct iova_fq *fq;
- fq = per_cpu_ptr(iovad->fq, cpu);
+ fq = per_cpu_ptr(queue, cpu);
fq->head = 0;
fq->tail = 0;
spin_lock_init(&fq->lock);
}
+ smp_wmb();
+
+ iovad->fq = queue;
+
timer_setup(&iovad->fq_timer, fq_flush_timeout, 0);
atomic_set(&iovad->fq_timer_on, 0);
diff --git a/include/linux/iova.h b/include/linux/iova.h
index 781b96ac706f..cd0f1de901a8 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -155,6 +155,7 @@ struct iova *reserve_iova(struct iova_domain *iovad, unsigned long pfn_lo,
void copy_reserved_iova(struct iova_domain *from, struct iova_domain *to);
void init_iova_domain(struct iova_domain *iovad, unsigned long granule,
unsigned long start_pfn);
+bool has_iova_flush_queue(struct iova_domain *iovad);
int init_iova_flush_queue(struct iova_domain *iovad,
iova_flush_cb flush_cb, iova_entry_dtor entry_dtor);
struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn);
@@ -235,6 +236,11 @@ static inline void init_iova_domain(struct iova_domain *iovad,
{
}
+bool has_iova_flush_queue(struct iova_domain *iovad)
+{
+ return false;
+}
+
static inline int init_iova_flush_queue(struct iova_domain *iovad,
iova_flush_cb flush_cb,
iova_entry_dtor entry_dtor)