[PATCH v2 4/5] x86/pci: disable MSI(-X) on all devices at shutdown

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Attempt to disable MSI(-X) capabilities on all PCI devices know by Xen at
shutdown.  Doing such disabling should facilitate kexec chained kernel from
booting more reliably, as device MSI(-X) interrupt generation should be
quiesced.

It would also prevent "Receive accept error" being raised as a result of
non-disabled interrupts targeting offline CPUs.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v1:
 - Split from bigger patch.
 - Iterate over all devices, even if the handler returns failure.
---
 xen/arch/x86/crash.c           |  1 +
 xen/arch/x86/include/asm/msi.h |  1 +
 xen/arch/x86/msi.c             | 18 ++++++++++++++++++
 xen/arch/x86/smp.c             |  1 +
 xen/drivers/passthrough/pci.c  | 33 +++++++++++++++++++++++++++++++++
 xen/include/xen/pci.h          |  4 ++++
 6 files changed, 58 insertions(+)

diff --git a/xen/arch/x86/crash.c b/xen/arch/x86/crash.c
index a789416ca3ae..c946225c0b9b 100644
--- a/xen/arch/x86/crash.c
+++ b/xen/arch/x86/crash.c
@@ -177,6 +177,7 @@ static void nmi_shootdown_cpus(void)
 
         disable_IO_APIC();
         hpet_disable();
+        pci_disable_msi_all();
     }
 }
 
diff --git a/xen/arch/x86/include/asm/msi.h b/xen/arch/x86/include/asm/msi.h
index 63adb19820e8..7f9e531f73e6 100644
--- a/xen/arch/x86/include/asm/msi.h
+++ b/xen/arch/x86/include/asm/msi.h
@@ -86,6 +86,7 @@ extern int pci_enable_msi(struct pci_dev *pdev, struct 
msi_info *msi,
 extern void pci_disable_msi(struct msi_desc *msi_desc);
 extern int pci_prepare_msix(u16 seg, u8 bus, u8 devfn, bool off);
 extern void pci_cleanup_msi(struct pci_dev *pdev);
+extern void pci_disable_msi_all(void);
 extern int setup_msi_irq(struct irq_desc *desc, struct msi_desc *msidesc);
 extern int __setup_msi_irq(struct irq_desc *desc, struct msi_desc *msidesc,
                            hw_irq_controller *handler);
diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index e2360579deda..c9fe942c46f3 100644
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -1248,6 +1248,24 @@ void pci_cleanup_msi(struct pci_dev *pdev)
     msi_free_irqs(pdev);
 }
 
+static int cf_check disable_msi(struct pci_dev *pdev, void *arg)
+{
+    msi_set_enable(pdev, 0);
+    msix_set_enable(pdev, 0);
+
+    return 0;
+}
+
+/* Disable MSI and/or MSI-X on all devices known by Xen. */
+void pci_disable_msi_all(void)
+{
+    int rc = pci_iterate_devices(disable_msi, NULL);
+
+    if ( rc )
+        printk(XENLOG_ERR
+               "Failed to disable MSI(-X) on some devices: %d\n", rc);
+}
+
 int pci_reset_msix_state(struct pci_dev *pdev)
 {
     unsigned int pos = pdev->msix_pos;
diff --git a/xen/arch/x86/smp.c b/xen/arch/x86/smp.c
index f931db0d71c6..f58c8d3cafe1 100644
--- a/xen/arch/x86/smp.c
+++ b/xen/arch/x86/smp.c
@@ -376,6 +376,7 @@ void smp_send_stop(void)
     local_irq_disable();
     disable_IO_APIC();
     hpet_disable();
+    pci_disable_msi_all();
 
     if ( num_online_cpus() > 1 )
     {
diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 777c6b1a7fdc..945118383f45 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -1803,6 +1803,39 @@ int iommu_do_pci_domctl(
     return ret;
 }
 
+struct segment_iter {
+    int (*handler)(struct pci_dev *pdev, void *arg);
+    void *arg;
+    int rc;
+};
+
+static int cf_check iterate_all(struct pci_seg *pseg, void *arg)
+{
+    struct segment_iter *iter = arg;
+    struct pci_dev *pdev;
+
+    list_for_each_entry ( pdev, &pseg->alldevs_list, alldevs_list )
+    {
+        int rc = iter->handler(pdev, iter->arg);
+
+        if ( !iter->rc )
+            iter->rc = rc;
+    }
+
+    return 0;
+}
+
+int pci_iterate_devices(int (*handler)(struct pci_dev *pdev, void *arg),
+                        void *arg)
+{
+    struct segment_iter iter = {
+        .handler = handler,
+        .arg = arg,
+    };
+
+    return pci_segments_iterate(iterate_all, &iter) ?: iter.rc;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
index f784e9116059..983c592124a8 100644
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -226,6 +226,10 @@ struct pci_dev *pci_get_pdev(const struct domain *d, 
pci_sbdf_t sbdf);
 struct pci_dev *pci_get_real_pdev(pci_sbdf_t sbdf);
 void pci_check_disable_device(u16 seg, u8 bus, u8 devfn);
 
+/* Iterate without locking or preemption over all PCI devices known by Xen. */
+int pci_iterate_devices(int (*handler)(struct pci_dev *pdev, void *arg),
+                        void *arg);
+
 uint8_t pci_conf_read8(pci_sbdf_t sbdf, unsigned int reg);
 uint16_t pci_conf_read16(pci_sbdf_t sbdf, unsigned int reg);
 uint32_t pci_conf_read32(pci_sbdf_t sbdf, unsigned int reg);
-- 
2.46.0