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[Xen-devel] [PATCH 2/2] vpci/msi: fix update of bound MSI interrupts

Current update process of already bound MSI interrupts is wrong
because unmap_domain_pirq calls pci_disable_msi, which disables MSI
interrupts on the device. On the other hand map_domain_pirq doesn't
enable MSI, so the current update process of already enabled MSI
entries is wrong because MSI control bit will be disabled by
unmap_domain_pirq and not re-enabled by map_domain_pirq.

In order to fix this avoid unmapping the PIRQs and just update the
binding of the PIRQ. A new arch helper to do that is introduced.

Note that MSI-X is not affected because unmap_domain_pirq only
disables the MSI enable control bit for the MSI case, for MSI-X the
bit is left untouched by unmap_domain_pirq.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
 xen/arch/x86/hvm/vmsi.c | 23 +++++++++++++++++++++++
 xen/drivers/vpci/msi.c  |  3 +--
 xen/include/xen/vpci.h  |  2 ++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vmsi.c b/xen/arch/x86/hvm/vmsi.c
index 6e19851439..8f9f84a6f3 100644
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -699,6 +699,29 @@ static int vpci_msi_update(const struct pci_dev *pdev, 
uint32_t data,
     return 0;
+int vpci_msi_arch_update(struct vpci_msi *msi, const struct pci_dev *pdev)
+    int rc;
+    ASSERT(msi->arch.pirq != INVALID_PIRQ);
+    pcidevs_lock();
+    rc = vpci_msi_update(pdev, msi->data, msi->address, msi->vectors,
+                         msi->arch.pirq, msi->mask);
+    if ( rc )
+    {
+        spin_lock(&pdev->domain->event_lock);
+        unmap_domain_pirq(pdev->domain, msi->arch.pirq);
+        spin_unlock(&pdev->domain->event_lock);
+        pcidevs_unlock();
+        msi->arch.pirq = INVALID_PIRQ;
+        return rc;
+    }
+    pcidevs_unlock();
+    return 0;
 static int vpci_msi_enable(const struct pci_dev *pdev, uint32_t data,
                            uint64_t address, unsigned int nr,
                            paddr_t table_base, uint32_t mask)
diff --git a/xen/drivers/vpci/msi.c b/xen/drivers/vpci/msi.c
index ad26c38a92..8f15ad7bf2 100644
--- a/xen/drivers/vpci/msi.c
+++ b/xen/drivers/vpci/msi.c
@@ -87,8 +87,7 @@ static void update_msi(const struct pci_dev *pdev, struct 
vpci_msi *msi)
     if ( !msi->enabled )
-    vpci_msi_arch_disable(msi, pdev);
-    if ( vpci_msi_arch_enable(msi, pdev, msi->vectors) )
+    if ( vpci_msi_arch_update(msi, pdev) )
         msi->enabled = false;
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index 72d2225a97..af2b8580ee 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -159,6 +159,8 @@ int __must_check vpci_msi_arch_enable(struct vpci_msi *msi,
                                       const struct pci_dev *pdev,
                                       unsigned int vectors);
 void vpci_msi_arch_disable(struct vpci_msi *msi, const struct pci_dev *pdev);
+int __must_check vpci_msi_arch_update(struct vpci_msi *msi,
+                                      const struct pci_dev *pdev);
 void vpci_msi_arch_init(struct vpci_msi *msi);
 void vpci_msi_arch_print(const struct vpci_msi *msi);

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