linux/virt/kvm
Andres Lagar-Cavilla 234b239bea kvm: Faults which trigger IO release the mmap_sem
When KVM handles a tdp fault it uses FOLL_NOWAIT. If the guest memory
has been swapped out or is behind a filemap, this will trigger async
readahead and return immediately. The rationale is that KVM will kick
back the guest with an "async page fault" and allow for some other
guest process to take over.

If async PFs are enabled the fault is retried asap from an async
workqueue. If not, it's retried immediately in the same code path. In
either case the retry will not relinquish the mmap semaphore and will
block on the IO. This is a bad thing, as other mmap semaphore users
now stall as a function of swap or filemap latency.

This patch ensures both the regular and async PF path re-enter the
fault allowing for the mmap semaphore to be relinquished in the case
of IO wait.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Andres Lagar-Cavilla <andreslc@google.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2014-09-24 14:07:54 +02:00
..
arm KVM: ARM: vgic: register kvm_device_ops dynamically 2014-09-17 13:10:09 +02:00
assigned-dev.c virt/kvm/assigned-dev.c: Set 'dev->irq_source_id' to '-1' after free it 2014-08-19 15:12:28 +02:00
async_pf.c kvm: Faults which trigger IO release the mmap_sem 2014-09-24 14:07:54 +02:00
async_pf.h KVM: Halt vcpu if page it tries to access is swapped out 2011-01-12 11:21:39 +02:00
coalesced_mmio.c KVM: return an error code in kvm_vm_ioctl_register_coalesced_mmio() 2014-01-30 11:56:09 +01:00
coalesced_mmio.h KVM: Make coalesced mmio use a device per zone 2011-09-25 19:17:57 +03:00
eventfd.c KVM: EVENTFD: Remove inclusion of irq.h 2014-09-24 12:06:25 +02:00
ioapic.c kvm: ioapic: conditionally delay irq delivery duringeoi broadcast 2014-09-16 14:44:48 +02:00
ioapic.h kvm: ioapic: conditionally delay irq delivery duringeoi broadcast 2014-09-16 14:44:48 +02:00
iodev.h KVM: remove in_range from io devices 2009-09-10 08:33:05 +03:00
iommu.c kvm: iommu: fix the third parameter of kvm_iommu_put_pages (CVE-2014-3601) 2014-08-19 15:04:45 +02:00
irq_comm.c KVM: Move all accesses to kvm::irq_routing into irqchip.c 2014-08-05 14:26:20 +02:00
irqchip.c KVM: Move irq notifier implementation into eventfd.c 2014-08-05 14:26:24 +02:00
Kconfig KVM: Give IRQFD its own separate enabling Kconfig option 2014-08-05 14:26:28 +02:00
kvm_main.c kvm: Faults which trigger IO release the mmap_sem 2014-09-24 14:07:54 +02:00
vfio.c kvm-vfio: do not use module_init 2014-09-24 14:06:36 +02:00
vfio.h kvm-vfio: do not use module_init 2014-09-24 14:06:36 +02:00