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Date: Thu, 16 May 2024 09:25:11 +0800
From: Henry Wang <xin.wang2@....com>
To: Stefano Stabellini <sstabellini@...nel.org>
CC: <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>, "Juergen
Gross" <jgross@...e.com>, Oleksandr Tyshchenko
<oleksandr_tyshchenko@...m.com>, Michal Orzel <michal.orzel@....com>
Subject: Re: [PATCH] drivers/xen: Improve the late XenStore init protocol
Hi Stefano,
On 5/16/2024 6:30 AM, Stefano Stabellini wrote:
> On Wed, 15 May 2024, Henry Wang wrote:
>> Currently, the late XenStore init protocol is only triggered properly
>> for the case that HVM_PARAM_STORE_PFN is ~0ULL (invalid). For the
>> case that XenStore interface is allocated but not ready (the connection
>> status is not XENSTORE_CONNECTED), Linux should also wait until the
>> XenStore is set up properly.
>>
>> Introduce a macro to describe the XenStore interface is ready, use
>> it in xenbus_probe_initcall() and xenbus_probe() to select the code
>> path of doing the late XenStore init protocol or not.
>>
>> Take the opportunity to enhance the check of the allocated XenStore
>> interface can be properly mapped, and return error early if the
>> memremap() fails.
>>
>> Signed-off-by: Henry Wang <xin.wang2@....com>
>> Signed-off-by: Michal Orzel <michal.orzel@....com>
> Please add a Fixes: tag
Sure. Will do.
>> ---
>> drivers/xen/xenbus/xenbus_probe.c | 21 ++++++++++++++++-----
>> 1 file changed, 16 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
>> index 3205e5d724c8..8aec0ed1d047 100644
>> --- a/drivers/xen/xenbus/xenbus_probe.c
>> +++ b/drivers/xen/xenbus/xenbus_probe.c
>> @@ -72,6 +72,10 @@ EXPORT_SYMBOL_GPL(xen_store_evtchn);
>> struct xenstore_domain_interface *xen_store_interface;
>> EXPORT_SYMBOL_GPL(xen_store_interface);
>>
>> +#define XS_INTERFACE_READY \
>> + ((xen_store_interface != NULL) && \
>> + (xen_store_interface->connection == XENSTORE_CONNECTED))
>> +
>> enum xenstore_init xen_store_domain_type;
>> EXPORT_SYMBOL_GPL(xen_store_domain_type);
>>
>> @@ -751,9 +755,10 @@ static void xenbus_probe(void)
>> {
>> xenstored_ready = 1;
>>
>> - if (!xen_store_interface) {
>> - xen_store_interface = memremap(xen_store_gfn << XEN_PAGE_SHIFT,
>> - XEN_PAGE_SIZE, MEMREMAP_WB);
>> + if (!xen_store_interface || XS_INTERFACE_READY) {
>> + if (!xen_store_interface)
> These two nested if's don't make sense to me. If XS_INTERFACE_READY
> succeeds, it means that ((xen_store_interface != NULL) &&
> (xen_store_interface->connection == XENSTORE_CONNECTED)).
>
> So it is not possible that xen_store_interface == NULL immediately
> after. Right?
I think this is because we want to free the irq for the late init case,
otherwise the init-dom0less will fail. For the xenstore PFN allocated
case, the connection is already set to CONNECTED when we execute
init-dom0less. But I agree with you, would below diff makes more sense
to you?
diff --git a/drivers/xen/xenbus/xenbus_probe.c
b/drivers/xen/xenbus/xenbus_probe.c
index 8aec0ed1d047..b8005b651a29 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -76,6 +76,8 @@ EXPORT_SYMBOL_GPL(xen_store_interface);
((xen_store_interface != NULL) && \
(xen_store_interface->connection == XENSTORE_CONNECTED))
+static bool xs_late_init = false;
+
enum xenstore_init xen_store_domain_type;
EXPORT_SYMBOL_GPL(xen_store_domain_type);
@@ -755,7 +757,7 @@ static void xenbus_probe(void)
{
xenstored_ready = 1;
- if (!xen_store_interface || XS_INTERFACE_READY) {
+ if (xs_late_init) {
if (!xen_store_interface)
xen_store_interface = memremap(xen_store_gfn <<
XEN_PAGE_SHIFT,
XEN_PAGE_SIZE, MEMREMAP_WB);
@@ -937,6 +939,8 @@ static irqreturn_t xenbus_late_init(int irq, void
*unused)
int err;
uint64_t v = 0;
+ xs_late_init = true;
+
err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
if (err || !v || !~v)
return IRQ_HANDLED;
>> + xen_store_interface = memremap(xen_store_gfn << XEN_PAGE_SHIFT,
>> + XEN_PAGE_SIZE, MEMREMAP_WB);
>> /*
>> * Now it is safe to free the IRQ used for xenstore late
>> * initialization. No need to unbind: it is about to be
>> @@ -822,7 +827,7 @@ static int __init xenbus_probe_initcall(void)
>> if (xen_store_domain_type == XS_PV ||
>> (xen_store_domain_type == XS_HVM &&
>> !xs_hvm_defer_init_for_callback() &&
>> - xen_store_interface != NULL))
>> + XS_INTERFACE_READY))
>> xenbus_probe();
>>
>> /*
>> @@ -831,7 +836,7 @@ static int __init xenbus_probe_initcall(void)
>> * started, then probe. It will be triggered when communication
>> * starts happening, by waiting on xb_waitq.
>> */
>> - if (xen_store_domain_type == XS_LOCAL || xen_store_interface == NULL) {
>> + if (xen_store_domain_type == XS_LOCAL || !XS_INTERFACE_READY) {
>> struct task_struct *probe_task;
>>
>> probe_task = kthread_run(xenbus_probe_thread, NULL,
>> @@ -1014,6 +1019,12 @@ static int __init xenbus_init(void)
>> xen_store_interface =
>> memremap(xen_store_gfn << XEN_PAGE_SHIFT,
>> XEN_PAGE_SIZE, MEMREMAP_WB);
>> + if (!xen_store_interface) {
>> + pr_err("%s: cannot map HVM_PARAM_STORE_PFN=%llx\n",
>> + __func__, v);
>> + err = -ENOMEM;
> I think this should -EINVAL
Will change.
Kind regards,
Henry
>> + goto out_error;
>> + }
>> if (xen_store_interface->connection != XENSTORE_CONNECTED)
>> wait = true;
>> }
>> --
>> 2.34.1
>>
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