From 3499ba8198cad47b731792e5e56b9ec2a78a83a2 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Wed, 13 Jan 2021 13:26:02 +0000 Subject: xen: Fix event channel callback via INTX/GSI For a while, event channel notification via the PCI platform device has been broken, because we attempt to communicate with xenstore before we even have notifications working, with the xs_reset_watches() call in xs_init(). We tend to get away with this on Xen versions below 4.0 because we avoid calling xs_reset_watches() anyway, because xenstore might not cope with reading a non-existent key. And newer Xen *does* have the vector callback support, so we rarely fall back to INTX/GSI delivery. To fix it, clean up a bit of the mess of xs_init() and xenbus_probe() startup. Call xs_init() directly from xenbus_init() only in the !XS_HVM case, deferring it to be called from xenbus_probe() in the XS_HVM case instead. Then fix up the invocation of xenbus_probe() to happen either from its device_initcall if the callback is available early enough, or when the callback is finally set up. This means that the hack of calling xenbus_probe() from a workqueue after the first interrupt, or directly from the PCI platform device setup, is no longer needed. Signed-off-by: David Woodhouse Reviewed-by: Boris Ostrovsky Link: https://lore.kernel.org/r/20210113132606.422794-2-dwmw2@infradead.org Signed-off-by: Juergen Gross --- drivers/xen/xenbus/xenbus_probe.c | 81 ++++++++++++++++++++++++++++++++------- 1 file changed, 67 insertions(+), 14 deletions(-) (limited to 'drivers/xen/xenbus/xenbus_probe.c') diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index 44634d970a5c..c8f0282bb649 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -683,29 +683,76 @@ void unregister_xenstore_notifier(struct notifier_block *nb) } EXPORT_SYMBOL_GPL(unregister_xenstore_notifier); -void xenbus_probe(struct work_struct *unused) +void xenbus_probe(void) { xenstored_ready = 1; + /* + * In the HVM case, xenbus_init() deferred its call to + * xs_init() in case callbacks were not operational yet. + * So do it now. + */ + if (xen_store_domain_type == XS_HVM) + xs_init(); + /* Notify others that xenstore is up */ blocking_notifier_call_chain(&xenstore_chain, 0, NULL); } -EXPORT_SYMBOL_GPL(xenbus_probe); -static int __init xenbus_probe_initcall(void) +/* + * Returns true when XenStore init must be deferred in order to + * allow the PCI platform device to be initialised, before we + * can actually have event channel interrupts working. + */ +static bool xs_hvm_defer_init_for_callback(void) { - if (!xen_domain()) - return -ENODEV; +#ifdef CONFIG_XEN_PVHVM + return xen_store_domain_type == XS_HVM && + !xen_have_vector_callback; +#else + return false; +#endif +} - if (xen_initial_domain() || xen_hvm_domain()) - return 0; +static int __init xenbus_probe_initcall(void) +{ + /* + * Probe XenBus here in the XS_PV case, and also XS_HVM unless we + * need to wait for the platform PCI device to come up. + */ + if (xen_store_domain_type == XS_PV || + (xen_store_domain_type == XS_HVM && + !xs_hvm_defer_init_for_callback())) + xenbus_probe(); - xenbus_probe(NULL); return 0; } - device_initcall(xenbus_probe_initcall); +int xen_set_callback_via(uint64_t via) +{ + struct xen_hvm_param a; + int ret; + + a.domid = DOMID_SELF; + a.index = HVM_PARAM_CALLBACK_IRQ; + a.value = via; + + ret = HYPERVISOR_hvm_op(HVMOP_set_param, &a); + if (ret) + return ret; + + /* + * If xenbus_probe_initcall() deferred the xenbus_probe() + * due to the callback not functioning yet, we can do it now. + */ + if (!xenstored_ready && xs_hvm_defer_init_for_callback()) + xenbus_probe(); + + return ret; +} +EXPORT_SYMBOL_GPL(xen_set_callback_via); + /* Set up event channel for xenstored which is run as a local process * (this is normally used only in dom0) */ @@ -818,11 +865,17 @@ static int __init xenbus_init(void) break; } - /* Initialize the interface to xenstore. */ - err = xs_init(); - if (err) { - pr_warn("Error initializing xenstore comms: %i\n", err); - goto out_error; + /* + * HVM domains may not have a functional callback yet. In that + * case let xs_init() be called from xenbus_probe(), which will + * get invoked at an appropriate time. + */ + if (xen_store_domain_type != XS_HVM) { + err = xs_init(); + if (err) { + pr_warn("Error initializing xenstore comms: %i\n", err); + goto out_error; + } } if ((xen_store_domain_type != XS_LOCAL) && -- cgit v1.2.3 From 5f46400f7a6a4fad635d5a79e2aa5a04a30ffea1 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Tue, 26 Jan 2021 17:01:49 +0000 Subject: xen: Fix XenStore initialisation for XS_LOCAL In commit 3499ba8198ca ("xen: Fix event channel callback via INTX/GSI") I reworked the triggering of xenbus_probe(). I tried to simplify things by taking out the workqueue based startup triggered from wake_waiting(); the somewhat poorly named xenbus IRQ handler. I missed the fact that in the XS_LOCAL case (Dom0 starting its own xenstored or xenstore-stubdom, which happens after the kernel is booted completely), that IRQ-based trigger is still actually needed. So... put it back, except more cleanly. By just spawning a xenbus_probe thread which waits on xb_waitq and runs the probe the first time it gets woken, just as the workqueue-based hack did. This is actually a nicer approach for *all* the back ends with different interrupt methods, and we can switch them all over to that without the complex conditions for when to trigger it. But not in -rc6. This is the minimal fix for the regression, although it's a step in the right direction instead of doing a partial revert and actually putting the workqueue back. It's also simpler than the workqueue. Fixes: 3499ba8198ca ("xen: Fix event channel callback via INTX/GSI") Reported-by: Juergen Gross Signed-off-by: David Woodhouse Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/4c9af052a6e0f6485d1de43f2c38b1461996db99.camel@infradead.org Signed-off-by: Juergen Gross --- drivers/xen/xenbus/xenbus_probe.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'drivers/xen/xenbus/xenbus_probe.c') diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index c8f0282bb649..18ffd0551b54 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -714,6 +714,23 @@ static bool xs_hvm_defer_init_for_callback(void) #endif } +static int xenbus_probe_thread(void *unused) +{ + DEFINE_WAIT(w); + + /* + * We actually just want to wait for *any* trigger of xb_waitq, + * and run xenbus_probe() the moment it occurs. + */ + prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE); + schedule(); + finish_wait(&xb_waitq, &w); + + DPRINTK("probing"); + xenbus_probe(); + return 0; +} + static int __init xenbus_probe_initcall(void) { /* @@ -725,6 +742,20 @@ static int __init xenbus_probe_initcall(void) !xs_hvm_defer_init_for_callback())) xenbus_probe(); + /* + * For XS_LOCAL, spawn a thread which will wait for xenstored + * or a xenstore-stubdom to be started, then probe. It will be + * triggered when communication starts happening, by waiting + * on xb_waitq. + */ + if (xen_store_domain_type == XS_LOCAL) { + struct task_struct *probe_task; + + probe_task = kthread_run(xenbus_probe_thread, NULL, + "xenbus_probe"); + if (IS_ERR(probe_task)) + return PTR_ERR(probe_task); + } return 0; } device_initcall(xenbus_probe_initcall); -- cgit v1.2.3 From c4295ab0b485b8bc50d2264bcae2acd06f25caaf Mon Sep 17 00:00:00 2001 From: Julien Grall Date: Wed, 10 Feb 2021 17:06:54 +0000 Subject: arm/xen: Don't probe xenbus as part of an early initcall After Commit 3499ba8198cad ("xen: Fix event channel callback via INTX/GSI"), xenbus_probe() will be called too early on Arm. This will recent to a guest hang during boot. If the hang wasn't there, we would have ended up to call xenbus_probe() twice (the second time is in xenbus_probe_initcall()). We don't need to initialize xenbus_probe() early for Arm guest. Therefore, the call in xen_guest_init() is now removed. After this change, there is no more external caller for xenbus_probe(). So the function is turned to a static one. Interestingly there were two prototypes for it. Cc: stable@vger.kernel.org Fixes: 3499ba8198cad ("xen: Fix event channel callback via INTX/GSI") Reported-by: Ian Jackson Signed-off-by: Julien Grall Reviewed-by: David Woodhouse Reviewed-by: Stefano Stabellini Link: https://lore.kernel.org/r/20210210170654.5377-1-julien@xen.org Signed-off-by: Juergen Gross --- arch/arm/xen/enlighten.c | 2 -- drivers/xen/xenbus/xenbus.h | 1 - drivers/xen/xenbus/xenbus_probe.c | 2 +- include/xen/xenbus.h | 2 -- 4 files changed, 1 insertion(+), 6 deletions(-) (limited to 'drivers/xen/xenbus/xenbus_probe.c') diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c index 5a957a9a0984..8ad576ecd0f1 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -370,8 +370,6 @@ static int __init xen_guest_init(void) return -ENOMEM; } gnttab_init(); - if (!xen_initial_domain()) - xenbus_probe(); /* * Making sure board specific code will not set up ops for diff --git a/drivers/xen/xenbus/xenbus.h b/drivers/xen/xenbus/xenbus.h index dc1537335414..2a93b7c9c159 100644 --- a/drivers/xen/xenbus/xenbus.h +++ b/drivers/xen/xenbus/xenbus.h @@ -115,7 +115,6 @@ int xenbus_probe_node(struct xen_bus_type *bus, const char *type, const char *nodename); int xenbus_probe_devices(struct xen_bus_type *bus); -void xenbus_probe(void); void xenbus_dev_changed(const char *node, struct xen_bus_type *bus); diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index 18ffd0551b54..8a75092bb148 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -683,7 +683,7 @@ void unregister_xenstore_notifier(struct notifier_block *nb) } EXPORT_SYMBOL_GPL(unregister_xenstore_notifier); -void xenbus_probe(void) +static void xenbus_probe(void) { xenstored_ready = 1; diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h index 2c43b0ef1e4d..bf3cfc7c35d0 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -192,8 +192,6 @@ void xs_suspend_cancel(void); struct work_struct; -void xenbus_probe(void); - #define XENBUS_IS_ERR_READ(str) ({ \ if (!IS_ERR(str) && strlen(str) == 0) { \ kfree(str); \ -- cgit v1.2.3