xen: Fix event channel callback via INTX/GSI

[ Upstream commit 3499ba8198cad47b731792e5e56b9ec2a78a83a2 ]

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 <dwmw@amazon.co.uk>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20210113132606.422794-2-dwmw2@infradead.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
David Woodhouse 2021-01-13 13:26:02 +00:00 committed by Greg Kroah-Hartman
parent acc402fa5b
commit a09d4e7acd
7 changed files with 70 additions and 35 deletions

View File

@ -371,7 +371,7 @@ static int __init xen_guest_init(void)
}
gnttab_init();
if (!xen_initial_domain())
xenbus_probe(NULL);
xenbus_probe();
/*
* Making sure board specific code will not set up ops for

View File

@ -1988,16 +1988,6 @@ static struct irq_chip xen_percpu_chip __read_mostly = {
.irq_ack = ack_dynirq,
};
int xen_set_callback_via(uint64_t via)
{
struct xen_hvm_param a;
a.domid = DOMID_SELF;
a.index = HVM_PARAM_CALLBACK_IRQ;
a.value = via;
return HYPERVISOR_hvm_op(HVMOP_set_param, &a);
}
EXPORT_SYMBOL_GPL(xen_set_callback_via);
#ifdef CONFIG_XEN_PVHVM
/* Vector callbacks are better than PCI interrupts to receive event
* channel notifications because we can receive vector callbacks on any

View File

@ -149,7 +149,6 @@ static int platform_pci_probe(struct pci_dev *pdev,
ret = gnttab_init();
if (ret)
goto grant_out;
xenbus_probe(NULL);
return 0;
grant_out:
gnttab_free_auto_xlat_frames();

View File

@ -115,6 +115,7 @@ 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);

View File

@ -57,16 +57,8 @@ DEFINE_MUTEX(xs_response_mutex);
static int xenbus_irq;
static struct task_struct *xenbus_task;
static DECLARE_WORK(probe_work, xenbus_probe);
static irqreturn_t wake_waiting(int irq, void *unused)
{
if (unlikely(xenstored_ready == 0)) {
xenstored_ready = 1;
schedule_work(&probe_work);
}
wake_up(&xb_waitq);
return IRQ_HANDLED;
}

View File

@ -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);
/*
* 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)
{
#ifdef CONFIG_XEN_PVHVM
return xen_store_domain_type == XS_HVM &&
!xen_have_vector_callback;
#else
return false;
#endif
}
static int __init xenbus_probe_initcall(void)
{
if (!xen_domain())
return -ENODEV;
/*
* 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();
if (xen_initial_domain() || xen_hvm_domain())
return 0;
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) &&

View File

@ -187,7 +187,7 @@ void xs_suspend_cancel(void);
struct work_struct;
void xenbus_probe(struct work_struct *);
void xenbus_probe(void);
#define XENBUS_IS_ERR_READ(str) ({ \
if (!IS_ERR(str) && strlen(str) == 0) { \