* [PATCH] KVM: Fix assigned device MSI-X entry setting leak
@ 2012-01-30 18:06 Alex Williamson
2012-01-30 18:24 ` Jan Kiszka
0 siblings, 1 reply; 3+ messages in thread
From: Alex Williamson @ 2012-01-30 18:06 UTC (permalink / raw)
To: kvm; +Cc: linux-kernel, alex.williamson, jan.kiszka
We need to prioritize our matching when setting MSI-X vector
entries. Unused entries should only be used if we don't find
an exact match or else we risk duplicating entries. This was
causing an ENOSPC return when trying to mask and unmask MSI-X
vectors based on guest MSI-X table updates.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
The faulting sequence went something like:
Start:
[0] entry 0, vector A
[1] entry 1, vector B
[2] entry 2, vector C
Set entry 1 to 0:
[0] entry 0, vector A
[1] entry 1->1, vector B->0
[2] entry 2, vector C
Set entry 2 to 0:
[0] entry 0, vector A
[1] entry 1->2, vector 0->0 <- incorrectly matched
[2] entry 2, vector C
Set entry 2 to C:
[0] entry 0, vector A
[1] entry 2->2, vector 0->C <- incorrectly matched again
[2] entry 2, vector C
Set entry 1 to B:
[0] entry 0, vector A
[1] entry 2, vector C
[2] entry 2, vector C
-ENOSPC
Userspace will need to test for this bug (or do we want to set
a feature flag?).
virt/kvm/assigned-dev.c | 21 +++++++++++++++------
1 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index 758e3b3..798a090 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -728,7 +728,7 @@ msix_nr_out:
static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm,
struct kvm_assigned_msix_entry *entry)
{
- int r = 0, i;
+ int r = 0, i, unused = -1;
struct kvm_assigned_dev_kernel *adev;
mutex_lock(&kvm->lock);
@@ -741,17 +741,26 @@ static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm,
goto msix_entry_out;
}
- for (i = 0; i < adev->entries_nr; i++)
- if (adev->guest_msix_entries[i].vector == 0 ||
- adev->guest_msix_entries[i].entry == entry->entry) {
+ for (i = 0; i < adev->entries_nr; i++) {
+ if (unused < 0 && !adev->guest_msix_entries[i].vector)
+ unused = i;
+
+ if (adev->guest_msix_entries[i].entry == entry->entry) {
adev->guest_msix_entries[i].entry = entry->entry;
adev->guest_msix_entries[i].vector = entry->gsi;
adev->host_msix_entries[i].entry = entry->entry;
break;
}
+ }
+
if (i == adev->entries_nr) {
- r = -ENOSPC;
- goto msix_entry_out;
+ if (unused < 0) {
+ r = -ENOSPC;
+ goto msix_entry_out;
+ }
+ adev->guest_msix_entries[unused].entry = entry->entry;
+ adev->guest_msix_entries[unused].vector = entry->gsi;
+ adev->host_msix_entries[unused].entry = entry->entry;
}
msix_entry_out:
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: Fix assigned device MSI-X entry setting leak
2012-01-30 18:06 [PATCH] KVM: Fix assigned device MSI-X entry setting leak Alex Williamson
@ 2012-01-30 18:24 ` Jan Kiszka
2012-01-30 18:35 ` Alex Williamson
0 siblings, 1 reply; 3+ messages in thread
From: Jan Kiszka @ 2012-01-30 18:24 UTC (permalink / raw)
To: Alex Williamson; +Cc: kvm, linux-kernel
On 2012-01-30 19:06, Alex Williamson wrote:
> We need to prioritize our matching when setting MSI-X vector
> entries. Unused entries should only be used if we don't find
> an exact match or else we risk duplicating entries. This was
> causing an ENOSPC return when trying to mask and unmask MSI-X
> vectors based on guest MSI-X table updates.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>
> ---
>
> The faulting sequence went something like:
>
> Start:
> [0] entry 0, vector A
> [1] entry 1, vector B
> [2] entry 2, vector C
>
> Set entry 1 to 0:
> [0] entry 0, vector A
> [1] entry 1->1, vector B->0
> [2] entry 2, vector C
>
> Set entry 2 to 0:
> [0] entry 0, vector A
> [1] entry 1->2, vector 0->0 <- incorrectly matched
> [2] entry 2, vector C
>
> Set entry 2 to C:
> [0] entry 0, vector A
> [1] entry 2->2, vector 0->C <- incorrectly matched again
> [2] entry 2, vector C
>
> Set entry 1 to B:
> [0] entry 0, vector A
> [1] entry 2, vector C
> [2] entry 2, vector C
> -ENOSPC
>
> Userspace will need to test for this bug (or do we want to set
> a feature flag?).
The latter is much simpler. We did it before.
>
> virt/kvm/assigned-dev.c | 21 +++++++++++++++------
> 1 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
> index 758e3b3..798a090 100644
> --- a/virt/kvm/assigned-dev.c
> +++ b/virt/kvm/assigned-dev.c
> @@ -728,7 +728,7 @@ msix_nr_out:
> static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm,
> struct kvm_assigned_msix_entry *entry)
> {
> - int r = 0, i;
> + int r = 0, i, unused = -1;
> struct kvm_assigned_dev_kernel *adev;
>
> mutex_lock(&kvm->lock);
> @@ -741,17 +741,26 @@ static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm,
> goto msix_entry_out;
> }
>
> - for (i = 0; i < adev->entries_nr; i++)
> - if (adev->guest_msix_entries[i].vector == 0 ||
> - adev->guest_msix_entries[i].entry == entry->entry) {
> + for (i = 0; i < adev->entries_nr; i++) {
> + if (unused < 0 && !adev->guest_msix_entries[i].vector)
> + unused = i;
> +
> + if (adev->guest_msix_entries[i].entry == entry->entry) {
> adev->guest_msix_entries[i].entry = entry->entry;
> adev->guest_msix_entries[i].vector = entry->gsi;
> adev->host_msix_entries[i].entry = entry->entry;
> break;
> }
> + }
> +
> if (i == adev->entries_nr) {
> - r = -ENOSPC;
> - goto msix_entry_out;
> + if (unused < 0) {
> + r = -ENOSPC;
> + goto msix_entry_out;
> + }
> + adev->guest_msix_entries[unused].entry = entry->entry;
> + adev->guest_msix_entries[unused].vector = entry->gsi;
> + adev->host_msix_entries[unused].entry = entry->entry;
> }
>
> msix_entry_out:
>
Looks good. Does it fix the masking problems?
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: Fix assigned device MSI-X entry setting leak
2012-01-30 18:24 ` Jan Kiszka
@ 2012-01-30 18:35 ` Alex Williamson
0 siblings, 0 replies; 3+ messages in thread
From: Alex Williamson @ 2012-01-30 18:35 UTC (permalink / raw)
To: Jan Kiszka; +Cc: kvm, linux-kernel
On Mon, 2012-01-30 at 19:24 +0100, Jan Kiszka wrote:
> On 2012-01-30 19:06, Alex Williamson wrote:
> > We need to prioritize our matching when setting MSI-X vector
> > entries. Unused entries should only be used if we don't find
> > an exact match or else we risk duplicating entries. This was
> > causing an ENOSPC return when trying to mask and unmask MSI-X
> > vectors based on guest MSI-X table updates.
> >
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> >
> > ---
> >
> > The faulting sequence went something like:
> >
> > Start:
> > [0] entry 0, vector A
> > [1] entry 1, vector B
> > [2] entry 2, vector C
> >
> > Set entry 1 to 0:
> > [0] entry 0, vector A
> > [1] entry 1->1, vector B->0
> > [2] entry 2, vector C
> >
> > Set entry 2 to 0:
> > [0] entry 0, vector A
> > [1] entry 1->2, vector 0->0 <- incorrectly matched
> > [2] entry 2, vector C
> >
> > Set entry 2 to C:
> > [0] entry 0, vector A
> > [1] entry 2->2, vector 0->C <- incorrectly matched again
> > [2] entry 2, vector C
> >
> > Set entry 1 to B:
> > [0] entry 0, vector A
> > [1] entry 2, vector C
> > [2] entry 2, vector C
> > -ENOSPC
> >
> > Userspace will need to test for this bug (or do we want to set
> > a feature flag?).
>
> The latter is much simpler. We did it before.
Yeah, the test is little cumbersome, I'll send a v2 with a feature flag.
> >
> > virt/kvm/assigned-dev.c | 21 +++++++++++++++------
> > 1 files changed, 15 insertions(+), 6 deletions(-)
> >
> > diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
> > index 758e3b3..798a090 100644
> > --- a/virt/kvm/assigned-dev.c
> > +++ b/virt/kvm/assigned-dev.c
> > @@ -728,7 +728,7 @@ msix_nr_out:
> > static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm,
> > struct kvm_assigned_msix_entry *entry)
> > {
> > - int r = 0, i;
> > + int r = 0, i, unused = -1;
> > struct kvm_assigned_dev_kernel *adev;
> >
> > mutex_lock(&kvm->lock);
> > @@ -741,17 +741,26 @@ static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm,
> > goto msix_entry_out;
> > }
> >
> > - for (i = 0; i < adev->entries_nr; i++)
> > - if (adev->guest_msix_entries[i].vector == 0 ||
> > - adev->guest_msix_entries[i].entry == entry->entry) {
> > + for (i = 0; i < adev->entries_nr; i++) {
> > + if (unused < 0 && !adev->guest_msix_entries[i].vector)
> > + unused = i;
> > +
> > + if (adev->guest_msix_entries[i].entry == entry->entry) {
> > adev->guest_msix_entries[i].entry = entry->entry;
> > adev->guest_msix_entries[i].vector = entry->gsi;
> > adev->host_msix_entries[i].entry = entry->entry;
> > break;
> > }
> > + }
> > +
> > if (i == adev->entries_nr) {
> > - r = -ENOSPC;
> > - goto msix_entry_out;
> > + if (unused < 0) {
> > + r = -ENOSPC;
> > + goto msix_entry_out;
> > + }
> > + adev->guest_msix_entries[unused].entry = entry->entry;
> > + adev->guest_msix_entries[unused].vector = entry->gsi;
> > + adev->host_msix_entries[unused].entry = entry->entry;
> > }
> >
> > msix_entry_out:
> >
>
> Looks good. Does it fix the masking problems?
It appears to, a 4-way rhel6 guest w/ assigned igb happily shifts it's
smp affinity around with irqbalance while running netperf in a loop.
Thanks,
Alex
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-01-30 18:06 [PATCH] KVM: Fix assigned device MSI-X entry setting leak Alex Williamson
2012-01-30 18:24 ` Jan Kiszka
2012-01-30 18:35 ` Alex Williamson
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