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authorKarimAllah Ahmed <karahmed@amazon.de>2016-08-27 00:55:36 +0300
committerDavid Vrabel <david.vrabel@citrix.com>2016-09-30 13:44:34 +0300
commit72a9b186292d98494f222226cfd24a1621796209 (patch)
tree62bf7896b9e9971a4106adf28dd22b8f3cba4c24 /drivers/xen/platform-pci.c
parentc8761e2016aa51a2829563b02a0a55913bdb0be8 (diff)
downloadlinux-72a9b186292d98494f222226cfd24a1621796209.tar.xz
xen: Remove event channel notification through Xen PCI platform device
Ever since commit 254d1a3f02eb ("xen/pv-on-hvm kexec: shutdown watches from old kernel") using the INTx interrupt from Xen PCI platform device for event channel notification would just lockup the guest during bootup. postcore_initcall now calls xs_reset_watches which will eventually try to read a value from XenStore and will get stuck on read_reply at XenBus forever since the platform driver is not probed yet and its INTx interrupt handler is not registered yet. That means that the guest can not be notified at this moment of any pending event channels and none of the per-event handlers will ever be invoked (including the XenStore one) and the reply will never be picked up by the kernel. The exact stack where things get stuck during xenbus_init: -xenbus_init -xs_init -xs_reset_watches -xenbus_scanf -xenbus_read -xs_single -xs_single -xs_talkv Vector callbacks have always been the favourite event notification mechanism since their introduction in commit 38e20b07efd5 ("x86/xen: event channels delivery on HVM.") and the vector callback feature has always been advertised for quite some time by Xen that's why INTx was broken for several years now without impacting anyone. Luckily this also means that event channel notification through INTx is basically dead-code which can be safely removed without impacting anybody since it has been effectively disabled for more than 4 years with nobody complaining about it (at least as far as I'm aware of). This commit removes event channel notification through Xen PCI platform device. Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Juergen Gross <jgross@suse.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Cc: Julien Grall <julien.grall@citrix.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Ross Lagerwall <ross.lagerwall@citrix.com> Cc: xen-devel@lists.xenproject.org Cc: linux-kernel@vger.kernel.org Cc: linux-pci@vger.kernel.org Cc: Anthony Liguori <aliguori@amazon.com> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Diffstat (limited to 'drivers/xen/platform-pci.c')
-rw-r--r--drivers/xen/platform-pci.c64
1 files changed, 0 insertions, 64 deletions
diff --git a/drivers/xen/platform-pci.c b/drivers/xen/platform-pci.c
index cf9666680c8c..b59c9455aae1 100644
--- a/drivers/xen/platform-pci.c
+++ b/drivers/xen/platform-pci.c
@@ -42,7 +42,6 @@
static unsigned long platform_mmio;
static unsigned long platform_mmio_alloc;
static unsigned long platform_mmiolen;
-static uint64_t callback_via;
static unsigned long alloc_xen_mmio(unsigned long len)
{
@@ -55,51 +54,6 @@ static unsigned long alloc_xen_mmio(unsigned long len)
return addr;
}
-static uint64_t get_callback_via(struct pci_dev *pdev)
-{
- u8 pin;
- int irq;
-
- irq = pdev->irq;
- if (irq < 16)
- return irq; /* ISA IRQ */
-
- pin = pdev->pin;
-
- /* We don't know the GSI. Specify the PCI INTx line instead. */
- return ((uint64_t)0x01 << 56) | /* PCI INTx identifier */
- ((uint64_t)pci_domain_nr(pdev->bus) << 32) |
- ((uint64_t)pdev->bus->number << 16) |
- ((uint64_t)(pdev->devfn & 0xff) << 8) |
- ((uint64_t)(pin - 1) & 3);
-}
-
-static irqreturn_t do_hvm_evtchn_intr(int irq, void *dev_id)
-{
- xen_hvm_evtchn_do_upcall();
- return IRQ_HANDLED;
-}
-
-static int xen_allocate_irq(struct pci_dev *pdev)
-{
- return request_irq(pdev->irq, do_hvm_evtchn_intr,
- IRQF_NOBALANCING | IRQF_TRIGGER_RISING,
- "xen-platform-pci", pdev);
-}
-
-static int platform_pci_resume(struct pci_dev *pdev)
-{
- int err;
- if (xen_have_vector_callback)
- return 0;
- err = xen_set_callback_via(callback_via);
- if (err) {
- dev_err(&pdev->dev, "platform_pci_resume failure!\n");
- return err;
- }
- return 0;
-}
-
static int platform_pci_probe(struct pci_dev *pdev,
const struct pci_device_id *ent)
{
@@ -138,21 +92,6 @@ static int platform_pci_probe(struct pci_dev *pdev,
platform_mmio = mmio_addr;
platform_mmiolen = mmio_len;
- if (!xen_have_vector_callback) {
- ret = xen_allocate_irq(pdev);
- if (ret) {
- dev_warn(&pdev->dev, "request_irq failed err=%d\n", ret);
- goto out;
- }
- callback_via = get_callback_via(pdev);
- ret = xen_set_callback_via(callback_via);
- if (ret) {
- dev_warn(&pdev->dev, "Unable to set the evtchn callback "
- "err=%d\n", ret);
- goto out;
- }
- }
-
max_nr_gframes = gnttab_max_grant_frames();
grant_frames = alloc_xen_mmio(PAGE_SIZE * max_nr_gframes);
ret = gnttab_setup_auto_xlat_frames(grant_frames);
@@ -184,9 +123,6 @@ static struct pci_driver platform_driver = {
.name = DRV_NAME,
.probe = platform_pci_probe,
.id_table = platform_pci_tbl,
-#ifdef CONFIG_PM
- .resume_early = platform_pci_resume,
-#endif
};
static int __init platform_pci_init(void)