HW42
7 years ago
parent
9491de3313
commit
ad64b001a0
@ -0,0 +1,195 @@
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From 292dcb5eb9ceedeb981eb926be566af8c99cbb26 Mon Sep 17 00:00:00 2001
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From: HW42 <hw42@ipsumj.de>
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Date: Tue, 12 Sep 2017 00:49:02 +0200
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Subject: [PATCH] xen-pciback: add attribute to allow MSI enable flag writes
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QEMU running in a stubdom needs to be able to set the MSI enable flag in
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the PCI config space. This adds an attribute 'allow_msi_enable' which
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when set for a PCI device allows writes to this flag. The toolstack will
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need to set this for stubdoms.
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This should not introduce any new security issues since a malicious
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guest (or stubdom) can already generate MSIs through other ways, see
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[1] page 8.
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[1]: https://invisiblethingslab.com/resources/2011/Software%20Attacks%20on%20Intel%20VT-d.pdf
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---
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drivers/xen/xen-pciback/conf_space_capability.c | 39 +++++++++++++++
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drivers/xen/xen-pciback/pci_stub.c | 65 +++++++++++++++++++++++++
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drivers/xen/xen-pciback/pciback.h | 1 +
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3 files changed, 105 insertions(+)
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diff --git a/drivers/xen/xen-pciback/conf_space_capability.c b/drivers/xen/xen-pciback/conf_space_capability.c
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index 7f83e9083e9d..793635238267 100644
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--- a/drivers/xen/xen-pciback/conf_space_capability.c
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+++ b/drivers/xen/xen-pciback/conf_space_capability.c
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@@ -189,6 +189,40 @@ static const struct config_field caplist_pm[] = {
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{}
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};
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+#define MSI_OK_BITS (PCI_MSI_FLAGS_ENABLE)
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+
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+static int msi_flags_write(struct pci_dev *dev, int offset, u16 new_value,
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+ void *data)
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+{
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+ int err;
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+ u16 old_value;
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+ struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);
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+
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+ if (xen_pcibk_permissive || dev_data->permissive)
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+ goto write;
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+
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+ err = pci_read_config_word(dev, offset, &old_value);
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+ if (err)
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+ return err;
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+
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+ if (!dev_data->allow_msi_enable
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+ || (new_value ^ old_value) & ~MSI_OK_BITS)
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+ return PCIBIOS_SET_FAILED;
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+
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+write:
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+ return pci_write_config_word(dev, offset, new_value);
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+}
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+
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+static const struct config_field caplist_msi[] = {
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+ {
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+ .offset = PCI_MSI_FLAGS,
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+ .size = 2,
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+ .u.w.read = xen_pcibk_read_config_word,
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+ .u.w.write = msi_flags_write,
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+ },
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+ {}
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+};
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+
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static struct xen_pcibk_config_capability xen_pcibk_config_capability_pm = {
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.capability = PCI_CAP_ID_PM,
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.fields = caplist_pm,
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@@ -197,11 +231,16 @@ static struct xen_pcibk_config_capability xen_pcibk_config_capability_vpd = {
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.capability = PCI_CAP_ID_VPD,
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.fields = caplist_vpd,
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};
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+static struct xen_pcibk_config_capability xen_pcibk_config_capability_msi = {
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+ .capability = PCI_CAP_ID_MSI,
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+ .fields = caplist_msi,
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+};
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int xen_pcibk_config_capability_init(void)
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{
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register_capability(&xen_pcibk_config_capability_vpd);
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register_capability(&xen_pcibk_config_capability_pm);
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+ register_capability(&xen_pcibk_config_capability_msi);
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return 0;
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}
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diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
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index 6331a95691a4..953866285ac1 100644
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--- a/drivers/xen/xen-pciback/pci_stub.c
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+++ b/drivers/xen/xen-pciback/pci_stub.c
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@@ -303,6 +303,8 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
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xen_pcibk_config_reset_dev(dev);
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xen_pcibk_config_free_dyn_fields(dev);
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+ dev_data->allow_msi_enable = 0;
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+
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xen_unregister_device_domain_owner(dev);
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spin_lock_irqsave(&found_psdev->lock, flags);
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@@ -1434,6 +1436,64 @@ static ssize_t permissive_show(struct device_driver *drv, char *buf)
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static DRIVER_ATTR(permissive, S_IRUSR | S_IWUSR, permissive_show,
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permissive_add);
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+static ssize_t allow_msi_enable_add(struct device_driver *drv, const char *buf,
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+ size_t count)
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+{
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+ int domain, bus, slot, func;
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+ int err;
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+ struct pcistub_device *psdev;
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+ struct xen_pcibk_dev_data *dev_data;
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+
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+ err = str_to_slot(buf, &domain, &bus, &slot, &func);
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+ if (err)
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+ goto out;
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+
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+ psdev = pcistub_device_find(domain, bus, slot, func);
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+ if (!psdev) {
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+ err = -ENODEV;
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+ goto out;
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+ }
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+
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+ dev_data = pci_get_drvdata(psdev->dev);
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+ /* the driver data for a device should never be null at this point */
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+ if (!dev_data) {
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+ err = -ENXIO;
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+ goto release;
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+ }
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+ dev_data->allow_msi_enable = 1;
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+release:
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+ pcistub_device_put(psdev);
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+out:
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+ if (!err)
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+ err = count;
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+ return err;
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+}
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+
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+static ssize_t allow_msi_enable_show(struct device_driver *drv, char *buf)
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+{
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+ struct pcistub_device *psdev;
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+ struct xen_pcibk_dev_data *dev_data;
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+ size_t count = 0;
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+ unsigned long flags;
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+ spin_lock_irqsave(&pcistub_devices_lock, flags);
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+ list_for_each_entry(psdev, &pcistub_devices, dev_list) {
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+ if (count >= PAGE_SIZE)
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+ break;
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+ if (!psdev->dev)
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+ continue;
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+ dev_data = pci_get_drvdata(psdev->dev);
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+ if (!dev_data || !dev_data->allow_msi_enable)
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+ continue;
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+ count +=
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+ scnprintf(buf + count, PAGE_SIZE - count, "%s\n",
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+ pci_name(psdev->dev));
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+ }
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+ spin_unlock_irqrestore(&pcistub_devices_lock, flags);
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+ return count;
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+}
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+static DRIVER_ATTR(allow_msi_enable, S_IRUSR | S_IWUSR, allow_msi_enable_show,
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+ allow_msi_enable_add);
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+
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static void pcistub_exit(void)
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{
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driver_remove_file(&xen_pcibk_pci_driver.driver, &driver_attr_new_slot);
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@@ -1443,6 +1503,8 @@ static void pcistub_exit(void)
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driver_remove_file(&xen_pcibk_pci_driver.driver, &driver_attr_quirks);
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driver_remove_file(&xen_pcibk_pci_driver.driver,
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&driver_attr_permissive);
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+ driver_remove_file(&xen_pcibk_pci_driver.driver,
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+ &driver_attr_allow_msi_enable);
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driver_remove_file(&xen_pcibk_pci_driver.driver,
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&driver_attr_irq_handlers);
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driver_remove_file(&xen_pcibk_pci_driver.driver,
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@@ -1533,6 +1595,9 @@ static int __init pcistub_init(void)
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if (!err)
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err = driver_create_file(&xen_pcibk_pci_driver.driver,
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&driver_attr_permissive);
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+ if (!err)
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+ err = driver_create_file(&xen_pcibk_pci_driver.driver,
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+ &driver_attr_allow_msi_enable);
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if (!err)
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err = driver_create_file(&xen_pcibk_pci_driver.driver,
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diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
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index 7af369b6aaa2..32006bb4dad1 100644
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--- a/drivers/xen/xen-pciback/pciback.h
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+++ b/drivers/xen/xen-pciback/pciback.h
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@@ -44,6 +44,7 @@ struct xen_pcibk_dev_data {
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struct list_head config_fields;
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struct pci_saved_state *pci_saved_state;
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unsigned int permissive:1;
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+ unsigned int allow_msi_enable:1;
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unsigned int warned_on_write:1;
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unsigned int enable_intx:1;
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unsigned int isr_on:1; /* Whether the IRQ handler is installed. */
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--
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2.14.1
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