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ivshmem: Don't update non-existent MSI routes

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As of commit 660c97eef6 ("ivshmem: use kvm irqfd for msi notifications"),
QEMU crashes with:

  kvm_irqchip_commit_routes: Assertion `ret == 0' failed.

if the ivshmem device is configured with more vectors than what the server
supports. This is caused by the ivshmem_vector_unmask() being called on
vectors that have not been initialized by ivshmem_add_kvm_msi_virq().

This commit fixes it by adding a simple check to the mask and unmask
callbacks.

Note that the opposite mismatch, if the server supplies more vectors than
what the device is configured for, is already handled and leads to output
like:

  Too many eventfd received, device has 1 vectors

To reproduce the assert, run:

  ivshmem-server -n 0

and QEMU with:

  -device ivshmem-doorbell,chardev=iv
  -chardev socket,path=/tmp/ivshmem_socket,id=iv

then load the Windows driver, at the time of writing available at:

https://github.com/virtio-win/kvm-guest-drivers-windows/tree/master/ivshmem

The issue is believed to have been masked by other guest drivers, notably
Linux ones, not enabling MSI-X on the device.

Fixes: 660c97eef6 ("ivshmem: use kvm irqfd for msi notifications")
Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20171211072110.9058-2-lprosek@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Ladi Prosek 2017-12-11 08:21:07 +01:00 committed by Paolo Bonzini
parent a8aa6197a2
commit e6a354be6e
1 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
hw/misc/ivshmem.c
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@ -316,6 +316,10 @@ static int ivshmem_vector_unmask(PCIDevice *dev, unsigned vector,
int ret;
IVSHMEM_DPRINTF("vector unmask %p %d\n", dev, vector);
if (!v->pdev) {
error_report("ivshmem: vector %d route does not exist", vector);
return -EINVAL;
}
ret = kvm_irqchip_update_msi_route(kvm_state, v->virq, msg, dev);
if (ret < 0) {
@ -330,12 +334,16 @@ static void ivshmem_vector_mask(PCIDevice *dev, unsigned vector)
{
IVShmemState *s = IVSHMEM_COMMON(dev);
EventNotifier *n = &s->peers[s->vm_id].eventfds[vector];
MSIVector *v = &s->msi_vectors[vector];
int ret;
IVSHMEM_DPRINTF("vector mask %p %d\n", dev, vector);
if (!v->pdev) {
error_report("ivshmem: vector %d route does not exist", vector);
return;
}
ret = kvm_irqchip_remove_irqfd_notifier_gsi(kvm_state, n,
s->msi_vectors[vector].virq);
ret = kvm_irqchip_remove_irqfd_notifier_gsi(kvm_state, n, v->virq);
if (ret != 0) {
error_report("remove_irqfd_notifier_gsi failed");
}