recipes-kernel: linux: add support for Xen

This patch adds support to enable Xen for ti-linux-staging. This
involves a kernel fragment specifying desired defconfig options as well
as two patches:

fix-rpmsg-xen.patch: This patch fixes the rpmsg_probe failure that
happens otherwise.

drivers-...-protocol.patch: This patch [1] is required for compatibility
with a patchset [2] for xen which fixes init-dom0less and hotplugging
for dom0less domains.

[1]: https://lore.kernel.org/xen-devel/[email protected]/
[2]: https://lore.kernel.org/all/alpine.DEB.2.22.394.2405241552240.2557291@ubuntu-linux-20-04-desktop/

Signed-off-by: Amneesh Singh <[email protected]>

recipes-kernel/linux/linux-ti-enable-xen.inc

@@ -0,0 +1,9 @@
+FILESEXTRAPATHS:prepend := "${THISDIR}/xen:"
+
+SRC_URI:append = " \
+        file://drivers-xen-improve-the-late-xenstore-init-protocol.patch \
+        file://fix-rpmsg-xen.patch \
+        file://xen.cfg \
+        "
+
+KERNEL_CONFIG_FRAGMENTS:append = " ${WORKDIR}/xen.cfg"

recipes-kernel/linux/linux-ti-staging-rt_%.bbappend

@@ -1,4 +1,6 @@
 SRCREV:tie-jailhouse = "782a2e18a2af099d5c53bc4ba9f59d24a0ce8467"
 
+include ${@bb.utils.contains('DISTRO_FEATURES', 'xen', 'linux-ti-enable-xen.inc', '', d)}
+
 PR:append = "_tisdk_8"
 

recipes-kernel/linux/linux-ti-staging_%.bbappend

@@ -1,4 +1,5 @@
 SRCREV:tie-jailhouse = "c76373e447c96b32fe08beceef7a499d16eaed96"
 
-PR:append = "_tisdk_5"
+include ${@bb.utils.contains('DISTRO_FEATURES', 'xen', 'linux-ti-enable-xen.inc', '', d)}
 
+PR:append = "_tisdk_5"

recipes-kernel/linux/xen/drivers-xen-improve-the-late-xenstore-init-protocol.patch

@@ -0,0 +1,116 @@
+Subject: [PATCH v2] drivers/xen: Improve the late XenStore init
+
+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() to select the code path of doing the
+late XenStore init protocol or not. Since now we have more than one
+condition for XenStore late init, rework the check in xenbus_probe()
+for the free_irq().
+
+Take the opportunity to enhance the check of the allocated XenStore
+interface can be properly mapped, and return error early if the
+memremap() fails.
+
+Fixes: 5b3353949e89 ("xen: add support for initializing xenstore later as HVM domain")
+Signed-off-by: Henry Wang <[email protected]>
+Signed-off-by: Michal Orzel <[email protected]>
+---
+v2:
+- Use -EINVAL for the memremap() check. (Stefano)
+- Add Fixes: tag. (Stefano)
+- Rework the condition for free_irq() in xenbus_probe(). (Stefano)
+---
+ drivers/xen/xenbus/xenbus_probe.c | 36 ++++++++++++++++++++-----------
+ 1 file changed, 23 insertions(+), 13 deletions(-)
+
+diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
+index 3205e5d724c8..1a9ded0cddcb 100644
+--- a/drivers/xen/xenbus/xenbus_probe.c
++++ b/drivers/xen/xenbus/xenbus_probe.c
+@@ -65,13 +65,17 @@
+ #include "xenbus.h"
+
+
+-static int xs_init_irq;
++static int xs_init_irq = -1;
+ int xen_store_evtchn;
+ 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);
+
+@@ -751,19 +755,19 @@ static void xenbus_probe(void)
+ {
+ 	xenstored_ready = 1;
+
+-	if (!xen_store_interface) {
++	if (!xen_store_interface)
+ 		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
+-		 * bound again from xb_init_comms. Note that calling
+-		 * unbind_from_irqhandler now would result in xen_evtchn_close()
+-		 * being called and the event channel not being enabled again
+-		 * afterwards, resulting in missed event notifications.
+-		 */
++	/*
++	 * Now it is safe to free the IRQ used for xenstore late
++	 * initialization. No need to unbind: it is about to be
++	 * bound again from xb_init_comms. Note that calling
++	 * unbind_from_irqhandler now would result in xen_evtchn_close()
++	 * being called and the event channel not being enabled again
++	 * afterwards, resulting in missed event notifications.
++	 */
++	if (xs_init_irq >= 0)
+ 		free_irq(xs_init_irq, &xb_waitq);
+-	}
+
+ 	/*
+ 	 * In the HVM case, xenbus_init() deferred its call to
+@@ -822,7 +826,7 @@ 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 +835,7 @@ 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 +1018,12 @@ 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 = -EINVAL;
++				goto out_error;
++			}
+ 			if (xen_store_interface->connection != XENSTORE_CONNECTED)
+ 				wait = true;
+ 		}
+--
+2.34.1

recipes-kernel/linux/xen/fix-rpmsg-xen.patch

@@ -0,0 +1,13 @@
+diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
+index 7d320f799ca1..96ba831cf73f 100644
+--- a/drivers/virtio/virtio_ring.c
++++ b/drivers/virtio/virtio_ring.c
+@@ -279,7 +279,7 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
+ 	 * the DMA API if we're a Xen guest, which at least allows
+ 	 * all of the sensible Xen configurations to work correctly.
+ 	 */
+-	if (xen_domain())
++	if (xen_pv_domain())
+ 		return true;
+
+ 	return false;

recipes-kernel/linux/xen/xen.cfg

@@ -0,0 +1,55 @@
+#
+# Xen Options
+#
+CONFIG_XEN=y
+CONFIG_XEN_DOM0=y
+CONFIG_MMU_NOTIFIER=y
+CONFIG_HIBERNATE_CALLBACKS=y
+CONFIG_SYS_HYPERVISOR=y
+CONFIG_XEN_BLKDEV_FRONTEND=y
+CONFIG_XEN_BLKDEV_BACKEND=y
+CONFIG_XEN_SCSI_FRONTEND=y
+CONFIG_XEN_NETDEV_FRONTEND=y
+CONFIG_XEN_NETDEV_BACKEND=y
+CONFIG_INPUT_MISC=y
+CONFIG_INPUT_XEN_KBDDEV_FRONTEND=y
+CONFIG_HVC_IRQ=y
+CONFIG_HVC_XEN=y
+CONFIG_HVC_XEN_FRONTEND=y
+CONFIG_XEN_WDT=m
+CONFIG_FB_SYS_FILLRECT=y
+CONFIG_FB_SYS_COPYAREA=y
+CONFIG_FB_SYS_IMAGEBLIT=y
+CONFIG_FB_SYS_FOPS=y
+CONFIG_FB_DEFERRED_IO=y
+CONFIG_XEN_FBDEV_FRONTEND=y
+CONFIG_XEN_BALLOON=y
+CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y
+CONFIG_XEN_SCRUB_PAGES_DEFAULT=y
+CONFIG_XEN_DEV_EVTCHN=y
+CONFIG_XEN_BACKEND=y
+CONFIG_XENFS=y
+CONFIG_XEN_COMPAT_XENFS=y
+CONFIG_XEN_SYS_HYPERVISOR=y
+CONFIG_XEN_XENBUS_FRONTEND=y
+CONFIG_XEN_GNTDEV=y
+CONFIG_XEN_GNTDEV_DMABUF=y
+CONFIG_XEN_GRANT_DEV_ALLOC=y
+CONFIG_XEN_GRANT_DMA_ALLOC=y
+CONFIG_SWIOTLB_XEN=y
+CONFIG_XEN_PRIVCMD=y
+CONFIG_DRM_XEN=y
+CONFIG_DRM_XEN_FRONTEND=y
+
+#
+# PL011 support
+#
+CONFIG_SERIAL_AMBA_PL011=y
+CONFIG_SERIAL_AMBA_PL011_CONSOLE=y
+
+#
+# Userspace IO Options
+#
+CONFIG_UIO=y
+CONFIG_UIO_CIF=y
+CONFIG_UIO_PDRV_GENIRQ=y