linux-kernel - [PATCH] xenbus: Allow PVH dom0 a non-local xenstore

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Message-ID: <20250503131935.1885-1-jason.andryuk@amd.com>
Date: Sat, 3 May 2025 09:19:35 -0400
From: Jason Andryuk <jason.andryuk@....com>
To: Juergen Gross <jgross@...e.com>, Stefano Stabellini
	<sstabellini@...nel.org>, Oleksandr Tyshchenko
	<oleksandr_tyshchenko@...m.com>
CC: Jason Andryuk <jason.andryuk@....com>, <xen-devel@...ts.xenproject.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] xenbus: Allow PVH dom0 a non-local xenstore

Make xenbus_init() allow a non-local xenstore for a PVH dom0 - it is
currently forced to XS_LOCAL.  With Hyperlaunch booting dom0 and a
xenstore stubdom, dom0 can be handled as a regular XS_HVM following the
late init path.

Drop the use of xen_initial_domain() and just check for the event
channel instead.  This matches the PV case where there is no check for
initial domain.

Check the full 64bit HVM_PARAM_STORE_EVTCHN value to catch the off
chance that high bits are set for the 32bit event channel.

Signed-off-by: Jason Andryuk <jason.andryuk@....com>
---
 drivers/xen/xenbus/xenbus_probe.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 6d32ffb01136..7604f70ee108 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -966,9 +966,15 @@ static int __init xenbus_init(void)
 	if (xen_pv_domain())
 		xen_store_domain_type = XS_PV;
 	if (xen_hvm_domain())
+	{
 		xen_store_domain_type = XS_HVM;
-	if (xen_hvm_domain() && xen_initial_domain())
-		xen_store_domain_type = XS_LOCAL;
+		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
+		if (err)
+			goto out_error;
+		xen_store_evtchn = (int)v;
+		if (!v)
+			xen_store_domain_type = XS_LOCAL;
+	}
 	if (xen_pv_domain() && !xen_start_info->store_evtchn)
 		xen_store_domain_type = XS_LOCAL;
 	if (xen_pv_domain() && xen_start_info->store_evtchn)
@@ -987,10 +993,6 @@ static int __init xenbus_init(void)
 		xen_store_interface = gfn_to_virt(xen_store_gfn);
 		break;
 	case XS_HVM:
-		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
-		if (err)
-			goto out_error;
-		xen_store_evtchn = (int)v;
 		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
 		if (err)
 			goto out_error;
-- 
2.34.1