Re: [Xen-devel] [PATCH] xen: reuse the same pirq allocated whendriver load first time

From: Stefano Stabellini
Date: Wed Jun 26 2013 - 14:08:17 EST

On Wed, 26 Jun 2013, Zhenzhong Duan wrote:
> On 2013-06-26 01:51, Stefano Stabellini wrote:
> > On Tue, 25 Jun 2013, DuanZhenzhong wrote:
> > > Stefano Stabellini wrote:
> > > > Trimming some of the people in CC
> > > >
> > > > On Mon, 24 Jun 2013, Zhenzhong Duan wrote:
> > > >
> > > > > On 2013-06-20 22:21, Stefano Stabellini wrote:
> > > > >
> > > > > > On Thu, 20 Jun 2013, Zhenzhong Duan wrote:
> > > > > >
> > > > > > > On 2013-06-05 20:50, Stefano Stabellini wrote:
> > > > > > >
> > > > > > > > On Wed, 5 Jun 2013, Zhenzhong Duan wrote:
> > > > > > > >
> > > > > > > > > Stefano Stabellini wrote:
> > > > > > > > >
> > > > > > > > > On Tue, 21 May 2013, Stefano Stabellini wrote:
> > > > > > > > > On Tue, 21 May 2013, Konrad Rzeszutek Wilk wrote:
> > > > > > > > > Looking at the hypervisor code I couldn't see anything
> > > > > > > > > obviously
> > > > > > > > > wrong.
> > > > > > > > > I think the culprit is "physdev_unmap_pirq":
> > > > > > > > >
> > > > > > > > > if ( is_hvm_domain(d) )
> > > > > > > > > {
> > > > > > > > > spin_lock(&d->event_lock);
> > > > > > > > > gdprintk(XENLOG_WARNING,"d%d, pirq: %d is %x %s,
> > > > > > > > > irq:
> > > > > > > > > %d\n",
> > > > > > > > > d->domain_id, pirq, domain_pirq_to_emuirq(d,
> > > > > > > > > pirq),
> > > > > > > > > domain_pirq_to_emuirq(d, pirq) == IRQ_UNBOUND ?
> > > > > > > > > "unbound" :
> > > > > > > > > "",
> > > > > > > > > domain_pirq_to_irq(d, pirq));
> > > > > > > > > if
> > > > > > > > > ( domain_pirq_to_emuirq(d, pirq) != IRQ_UNBOUND )
> > > > > > > > > ret = unmap_domain_pirq_emuirq(d, pirq);
> > > > > > > > > spin_unlock(&d->event_lock);
> > > > > > > > > if ( domid == DOMID_SELF || ret )
> > > > > > > > > goto free_domain;
> > > > > > > > >
> > > > > > > > > It always tells me unbound:
> > > > > > > > >
> > > > > > > > > (XEN) physdev.c:237:d14 14, pirq: 54 is ffffffff
> > > > > > > > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > > > > > > > (XEN) physdev.c:237:d14 14, pirq: 53 is ffffffff
> > > > > > > > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > > > > > > > (XEN) physdev.c:237:d14 14, pirq: 52 is ffffffff
> > > > > > > > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > > > > > > > (XEN) physdev.c:237:d14 14, pirq: 51 is ffffffff
> > > > > > > > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > > > > > > > (XEN) physdev.c:237:d14 14, pirq: 50 is ffffffff
> > > > > > > > > (XEN) irq.c:1873:d14 14, nr_pirqs: 56
> > > > > > > > > (a bit older debug code, so the 'unbound' does not show up
> > > > > > > > > here).
> > > > > > > > >
> > > > > > > > > Which means that the call to unmap_domain_pirq_emuirq does not
> > > > > > > > > happen.
> > > > > > > > > The checks in unmap_domain_pirq_emuirq also look to be depend
> > > > > > > > > on the code being IRQ_UNBOUND.
> > > > > > > > >
> > > > > > > > > In other words, all of that code looks to only clear things
> > > > > > > > > when
> > > > > > > > > they are !IRQ_UNBOUND.
> > > > > > > > >
> > > > > > > > > But the other logic (IRQ_UNBOUND) looks to be missing a
> > > > > > > > > removal
> > > > > > > > > in the radix tree:
> > > > > > > > >
> > > > > > > > > if ( emuirq != IRQ_PT )
> > > > > > > > > radix_tree_delete(&d->arch.hvm_domain.emuirq_pirq,
> > > > > > > > > emuirq);
> > > > > > > > > And
> > > > > > > > > I think that is what is causing the leak - the radix tree
> > > > > > > > > needs to be pruned? Or perhaps the allocate_pirq should check
> > > > > > > > > the radix tree for IRQ_UNBOUND ones and re-use them?
> > > > > > > > > I think that you are looking in the wrong place.
> > > > > > > > > The issue is that QEMU doesn't call pt_msi_disable in
> > > > > > > > > pt_msgctrl_reg_write if (!val & PCI_MSI_FLAGS_ENABLE).
> > > > > > > > >
> > > > > > > > > The code above is correct as is because it is trying to handle
> > > > > > > > > emulated
> > > > > > > > > IRQs and MSIs, not real passthrough MSIs. They latter are not
> > > > > > > > > added to
> > > > > > > > > that radix tree, see physdev_hvm_map_pirq and
> > > > > > > > > physdev_map_pirq.
> > > > > > > > > This patch fixes the issue, I have only tested MSI
> > > > > > > > > (MSI-X
> > > > > > > > > completely
> > > > > > > > > untested).
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > diff --git a/hw/pass-through.c b/hw/pass-through.c
> > > > > > > > > index 304c438..079e465 100644
> > > > > > > > > --- a/hw/pass-through.c
> > > > > > > > > +++ b/hw/pass-through.c
> > > > > > > > > @@ -3866,7 +3866,11 @@ static int pt_msgctrl_reg_write(struct
> > > > > > > > > pt_dev
> > > > > > > > > *ptdev,
> > > > > > > > > ptdev->msi->flags |= PCI_MSI_FLAGS_ENABLE;
> > > > > > > > > }
> > > > > > > > > else
> > > > > > > > > - ptdev->msi->flags &= ~PCI_MSI_FLAGS_ENABLE;
> > > > > > > > > + {
> > > > > > > > > + if (ptdev->msi->flags & PT_MSI_MAPPED) {
> > > > > > > > > + pt_msi_disable(ptdev);
> > > > > > > > > + }
> > > > > > > > > + }
> > > > > > > > > /* pass through MSI_ENABLE bit when no MSI-INTx
> > > > > > > > > translation
> > > > > > > > > */
> > > > > > > > > if (!ptdev->msi_trans_en) {
> > > > > > > > > @@ -4013,6 +4017,8 @@ static int pt_msixctrl_reg_write(struct
> > > > > > > > > pt_dev
> > > > > > > > > *ptdev,
> > > > > > > > > pt_disable_msi_translate(ptdev);
> > > > > > > > > }
> > > > > > > > > pt_msix_update(ptdev);
> > > > > > > > > + } else if (!(*value & PCI_MSIX_ENABLE) &&
> > > > > > > > > ptdev->msix->enabled) {
> > > > > > > > > + pt_msix_delete(ptdev);
> > > > > > > > > Hi Stefano,
> > > > > > > > > I made a test with this patch, os reboot when driver reload.
> > > > > > > > > If
> > > > > > > > > use
> > > > > > > > > pt_msix_disable
> > > > > > > > > instead of pt_msix_delete, driver could be reloaded.
> > > > > > > > > But I still see some error in qemu.log and xen console. Seems
> > > > > > > > > four
> > > > > > > > > IRQs
> > > > > > > > > are not freed
> > > > > > > > > when unmap.
> > > > > > > > > --------------first load---------------------------
> > > > > > > > > pt_msix_update_one: pt_msix_update_one requested pirq = 103
> > > > > > > > > pt_msix_update_one: Update msix entry 0 with pirq 67 gvec 0
> > > > > > > > > pt_msix_update_one: pt_msix_update_one requested pirq = 102
> > > > > > > > > pt_msix_update_one: Update msix entry 1 with pirq 66 gvec 0
> > > > > > > > > pt_msix_update_one: pt_msix_update_one requested pirq = 101
> > > > > > > > > pt_msix_update_one: Update msix entry 2 with pirq 65 gvec 0
> > > > > > > > > pt_msix_update_one: pt_msix_update_one requested pirq = 100
> > > > > > > > > pt_msix_update_one: Update msix entry 3 with pirq 64 gvec 0
> > > > > > > > > ------------- first unload---------------------------
> > > > > > > > > pt_msix_disable: Unbind msix with pirq 67, gvec 0
> > > > > > > > > pt_msix_disable: Unmap msix with pirq 67
> > > > > > > > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > > > > > > > pt_msix_disable: Unbind msix with pirq 66, gvec 0
> > > > > > > > > pt_msix_disable: Unmap msix with pirq 66
> > > > > > > > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > > > > > > > pt_msix_disable: Unbind msix with pirq 65, gvec 0
> > > > > > > > > pt_msix_disable: Unmap msix with pirq 65
> > > > > > > > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > > > > > > > pt_msix_disable: Unbind msix with pirq 64, gvec 0
> > > > > > > > > pt_msix_disable: Unmap msix with pirq 64
> > > > > > > > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > > > > > > >
> > > > > > > > Can you add some printks in Xen (the hypercall name is
> > > > > > > > PHYSDEVOP_unmap_pirq) to figure out exactly why they are
> > > > > > > > failing?
> > > > > > > >
> > > > > > > Did some test, domain_pirq_to_emuirq(d, unmap->pirq) = IRQ_UNBOUND
> > > > > > > in
> > > > > > > physdev_unmap_pirq.
> > > > > > >
> > > > > > That means that Linux didn't call irq_enable on the MSI-X in
> > > > > > question:
> > > > > >
> > > > > > irq_enable -> __startup_pirq -> EVTCHNOP_bind_pirq
> > > > > >
> > > > > > EVTCHNOP_bind_pirq is implemented by evtchn_bind_pirq in Xen and
> > > > > > calls
> > > > > > map_domain_emuirq_pirq, so domain_pirq_to_emuirq(d, unmap->pirq)
> > > > > > should
> > > > > > be IRQ_PT.
> > > > > >
> > > > > > I don't know if that's a normal condition, but in any case it should
> > > > > > not create any problems to physdev_unmap_pirq, in fact the folloing
> > > > > > check:
> > > > > >
> > > > > > if ( domid == DOMID_SELF || ret )
> > > > > > goto free_domain;
> > > > > >
> > > > > > should fail so Xen should continue and execute unmap_domain_pirq.
> > > > > > That's
> > > > > > what we want.
> > > > > >
> > > > > From linux side, request_irq-> request_threaded_irq-> __setup_irq->
> > > > > irq_startup-> startup_pirq-> EVTCHNOP_bind_pirq
> > > > > If irq_enable isn't called, how does the driver receive interrupt, I
> > > > > did
> > > > > see
> > > > > four interrupts in /proc/interrupt and driver works ok.
> > > > >
> > > > Good to know
> > > >
> > > >
> > > > > Could you have a look if there is something wrong in xen side of
> > > > > clearing
> > > > > the
> > > > > mapping?
> > > > >
> > > > What I am saying is that the error you are getting:
> > > >
> > > > pt_msix_disable: Unbind msix with pirq 67, gvec 0
> > > > pt_msix_disable: Unmap msix with pirq 67
> > > > pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
> > > >
> > > > cannot be caused by domain_pirq_to_emuirq(d, pirq) returning
> > > > IRQ_UNBOUND.
> > > > So, why are you getting this error? What is failing?
> > > > I am ready to believe the problem is in Xen but Without understanding
> > > > why you are getting the error it's hard to find a solution.
> > > >
> > > I found the reason, you are looking at xen-unstable, I was working with
> > > 4.1.30-OVM, it has patch of CVE-2012-4536 / XSA-21.
> > > That patch set ret to -EINVAL initially. After remove that line, unmap
> > > succeed.
> > > But we still need below patch to let driver reload succeed everytime.
> > > Without
> > > that, 1st reload failed, 2nd succeed, 3 failed, ...
> > >
> > > diff -up --new-file ./hw/pt-msi.c.old1 ./hw/pt-msi.c
> > > --- ./hw/pt-msi.c.old1 2013-06-26 01:36:08.000000000 +0800
> > > +++ ./hw/pt-msi.c 2013-06-26 01:37:41.000000000 +0800
> > > @@ -469,7 +469,7 @@ static void pci_msix_writel(void *opaque
> > > return;
> > > }
> > >
> > > - if ( offset != 3 && entry->io_mem[offset] != val )
> > > + if ( offset != 3 && (entry->io_mem[offset] != val || entry->pirq ==
> > > -1))
> > > entry->flags = 1;
> > > entry->io_mem[offset] = val;
> > Interesting. I don't think this is the proper fix though.
> > Does the appended patch change anything?
> >
> > diff --git a/hw/pt-msi.c b/hw/pt-msi.c
> > index 71fa6f0..cd5d9c7 100644
> > --- a/hw/pt-msi.c
> > +++ b/hw/pt-msi.c
> > @@ -302,7 +302,7 @@ static int pt_msix_update_one(struct pt_dev *dev, int
> > entry_nr)
> > uint32_t gflags = __get_msi_gflags(entry->io_mem[2], gaddr);
> > int ret;
> > - if ( !entry->flags )
> > + if ( !entry->flags && ptdev->msix->enabled )
> > return 0;
> > if (!gvec) {
> Tested, not work.
> If you look at msix_capability_init in kernel, line 707,722,
> dev->msix->enabled is already set when pt_msix_update is called.

Yeah, but it shouldn't be already set in QEMU. In fact in QEMU
dev->msix->enabled is modified in pt_msixctrl_reg_write after calling to
pt_msix_update.


I was assuming that you needed to add "|| entry->pirq == -1" because you
needed to pass the check:

if ( !entry->flags )
return 0;

at the beginning of pt_msix_update_one. Am I getting it right?

If that is case that I thought that we just needed to make sure that
when ptdev->msix->enabled is still zero then we go through the test in
pt_msix_update_one. Where is the mistake?
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