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Message-ID: <e316cb7e-6f73-4aff-8533-c73539f4ae91@email.android.com>
Date: Thu, 29 Aug 2013 09:31:55 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: zhenzhong.duan@...cle.com,
Zhenzhong Duan <zhenzhong.duan@...cle.com>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
xen-devel <xen-devel@...ts.xen.org>
CC: Bjorn Helgaas <bhelgaas@...gle.com>, Feng Jin <joe.jin@...cle.com>,
Sucheta Chakraborty <sucheta.chakraborty@...gic.com>
Subject: Re: [PATCH 2/3 v3] Refactor MSI restore call-chain to drop unnecessary argument
Zhenzhong Duan <zhenzhong.duan@...cle.com> wrote:
>Driver init call graph under baremetal:
>driver_init->
> msix_capability_init->
> msix_program_entries->
> msix_mask_irq->
> entry->masked = 1
> request_irq->
> __setup_irq->
> irq_startup->
> unmask_msi_irq->
> msix_mask_irq->
> entry->masked = 0
>
>So entry->masked is always updated with newest value and its value
>could be used
>to restore to mask register in device.
>
>But in initial domain (aka priviliged guest), it's different.
>Driver init call graph under initial domain:
>driver_init->
> msix_capability_init->
> msix_program_entries->
> msix_mask_irq->
> entry->masked = 1
> request_irq->
> __setup_irq->
> irq_startup->
> __startup_pirq->
> EVTCHNOP_bind_pirq hypercall (trap into Xen)
>[Xen:]
>pirq_guest_bind->
> startup_msi_irq->
> unmask_msi_irq->
> msi_set_mask_bit->
> entry->msi_attrib.masked = 0
>
>So entry->msi_attrib.masked in xen side always has newest value.
>entry->masked
>in initial domain is untouched and is 1 after msix_capability_init.
>
>Based on above, it's Xen's duty to restore entry->msi_attrib.masked to
>device,
>but with current code, entry->masked is used and MSI-x interrupt is
>masked.
>
>Before patch, restore call graph under initial domain:
>pci_reset_function->
> pci_restore_state->
> __pci_restore_msix_state->
> arch_restore_msi_irqs->
> xen_initdom_restore_msi_irqs->
> PHYSDEVOP_restore_msi hypercall (first mask restore)
> msix_mask_irq(entry, entry->masked) (second mask restore)
>
>So msix_mask_irq call in initial domain call graph needs to be removed.
>
>Based on this we can move the restore of the mask in
>default_restore_msi_irqs
>which would avoid restoring the invalid mask under Xen. Furthermore
>this
>simplifies the API by making everything related to restoring an MSI be
>in the
>platform specific APIs instead of just parts of it.
>
>After patch, restore call graph under initial domain:
>pci_reset_function->
> pci_restore_state->
> __pci_restore_msix_state->
> arch_restore_msi_irqs->
> xen_initdom_restore_msi_irqs->
> PHYSDEVOP_restore_msi hypercall (first mask restore)
>
>Logic for baremetal is not changed.
>Before patch, restore call graph under baremetal:
>pci_reset_function->
> pci_restore_state->
> __pci_restore_msix_state->
> arch_restore_msi_irqs->
> default_restore_msi_irqs->
> msix_mask_irq(entry, entry->masked) (first mask restore)
>
>After patch, restore call graph under baremetal:
>pci_reset_function->
> pci_restore_state->
> __pci_restore_msix_state->
> arch_restore_msi_irqs->
> default_restore_msi_irqs->
> msix_mask_irq(entry, entry->masked) (first mask restore)
>
>The process for MSI code is similiar.
>
>-v3: Update patch description per Konrad suggestion, thanks.
>
>Tested-by: Sucheta Chakraborty <sucheta.chakraborty@...gic.com>
>Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
Bjorn,
If this is not too late to add to your queue please add it with my Acked-By.
Thanks.
>---
> drivers/pci/msi.c | 17 ++++++++++++++---
> 1 files changed, 14 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
>index 87223ae..922fb49 100644
>--- a/drivers/pci/msi.c
>+++ b/drivers/pci/msi.c
>@@ -216,6 +216,8 @@ void unmask_msi_irq(struct irq_data *data)
> #ifdef HAVE_DEFAULT_MSI_RESTORE_IRQS
> void default_restore_msi_irqs(struct pci_dev *dev, int irq)
> {
>+ int pos;
>+ u16 control;
> struct msi_desc *entry;
>
> entry = NULL;
>@@ -228,8 +230,19 @@ void default_restore_msi_irqs(struct pci_dev *dev,
>int irq)
> entry = irq_get_msi_desc(irq);
> }
>
>- if (entry)
>+ if (entry) {
> write_msi_msg(irq, &entry->msg);
>+ if (dev->msix_enabled) {
>+ msix_mask_irq(entry, entry->masked);
>+ readl(entry->mask_base);
>+ } else {
>+ pos = entry->msi_attrib.pos;
>+ pci_read_config_word(dev, pos + PCI_MSI_FLAGS,
>+ &control);
>+ msi_mask_irq(entry, msi_capable_mask(control),
>+ entry->masked);
>+ }
>+ }
> }
> #endif
>
>@@ -406,7 +419,6 @@ static void __pci_restore_msi_state(struct pci_dev
>*dev)
> arch_restore_msi_irqs(dev, dev->irq);
>
> pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
>- msi_mask_irq(entry, msi_capable_mask(control), entry->masked);
> control &= ~PCI_MSI_FLAGS_QSIZE;
> control |= (entry->msi_attrib.multiple << 4) | PCI_MSI_FLAGS_ENABLE;
> pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
>@@ -430,7 +442,6 @@ static void __pci_restore_msix_state(struct pci_dev
>*dev)
>
> list_for_each_entry(entry, &dev->msi_list, list) {
> arch_restore_msi_irqs(dev, entry->irq);
>- msix_mask_irq(entry, entry->masked);
> }
>
> control &= ~PCI_MSIX_FLAGS_MASKALL;
--
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