Re: dom0 bootstrap for xenstore

[Rusty Russell <rusty@rustcorp.com.au>]

On Thu, 2005-06-16 at 06:17 +0100, Keir Fraser wrote:
> > I suggested that we simply mmap /dev/kmem for the xenstored to access
> > the domain0 page for the moment.  That doesn't work: we'll do something
> > else.
> 
> Just use xc_map_foreign_range(), as you would for mapping any other 
> domain's xenstore page.

So here's my patch against latest bk, including test program but we have
an issue.  On unmap, I hit the BUG_ON() on mm/rmap.c:482.  Is this some
issue with using xc_map_foreign_range() on non-foreign pages?

Rusty.
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal xen/linux-2.6.11-xen-sparse/drivers/xen/privcmd/privcmd.c xen-dom0-store/linux-2.6.11-xen-sparse/drivers/xen/privcmd/privcmd.c
--- xen/linux-2.6.11-xen-sparse/drivers/xen/privcmd/privcmd.c	2005-06-16 18:03:10.000000000 +1000
+++ xen-dom0-store/linux-2.6.11-xen-sparse/drivers/xen/privcmd/privcmd.c	2005-06-16 15:12:49.000000000 +1000
@@ -196,6 +196,34 @@ static int privcmd_ioctl(struct inode *i
     }
     break;
 
+    case IOCTL_PRIVCMD_INITDOMAIN_STORE:
+    {
+        extern int do_xenbus_probe(void*);
+
+        if (xen_start_info.store_evtchn != 0) {
+	    ret = -EINVAL;
+	    break;
+	}
+
+	/* Allocate page. */
+	xen_start_info.store_page = get_zeroed_page(GFP_KERNEL);
+	if (!xen_start_info.store_page) {
+	    ret = -ENOMEM;
+	    break;
+	}
+
+	/* Initial connect. Setup channel and page. */
+	xen_start_info.store_evtchn = data;
+	ret = pfn_to_mfn(virt_to_phys((void *)xen_start_info.store_page)
+			 >> PAGE_SHIFT);
+
+	strcpy((char *)xen_start_info.store_page, "HELLO THERE!");
+
+	/* We'll return then this will wait for daemon to answer */
+	//kthread_run(do_xenbus_probe, NULL, "xenbus_probe");
+    }
+    break;
+
     default:
         ret = -EINVAL;
         break;
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal xen/linux-2.6.11-xen-sparse/include/asm-xen/linux-public/privcmd.h xen-dom0-store/linux-2.6.11-xen-sparse/include/asm-xen/linux-public/privcmd.h
--- xen/linux-2.6.11-xen-sparse/include/asm-xen/linux-public/privcmd.h	2005-06-16 18:03:13.000000000 +1000
+++ xen-dom0-store/linux-2.6.11-xen-sparse/include/asm-xen/linux-public/privcmd.h	2005-06-16 13:47:48.000000000 +1000
@@ -84,5 +84,7 @@ typedef struct privcmd_blkmsg
     _IOC(_IOC_NONE, 'P', 3, sizeof(privcmd_mmapbatch_t))
 #define IOCTL_PRIVCMD_GET_MACH2PHYS_START_MFN \
     _IOC(_IOC_READ, 'P', 4, sizeof(unsigned long))
+#define IOCTL_PRIVCMD_INITDOMAIN_STORE \
+    _IOC(_IOC_READ, 'P', 5, 0)
 
 #endif /* __PRIVCMD_H__ */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal xen/tools/xenstore/Makefile xen-dom0-store/tools/xenstore/Makefile
--- xen/tools/xenstore/Makefile	2005-06-16 18:03:27.000000000 +1000
+++ xen-dom0-store/tools/xenstore/Makefile	2005-06-16 14:46:51.000000000 +1000
@@ -82,18 +82,22 @@ stresstest: xs_stress xenstored_test
 	rm -rf $(TESTDIR)/store
 	export $(TESTENV); PID=`./xenstored_test --output-pid`; ./xs_stress 10000; ret=$$?; kill $$PID; exit $$ret
 
+xs_dom0_test: xs_dom0_test.o utils.o
+	$(LINK.o) $^ $(LOADLIBES) $(LDLIBS) -lxc -o $@
+
 TAGS:
 	etags `find . -name '*.[ch]'`
 
 tarball: clean
 	cd .. && tar -c -j -v -h -f xenstore.tar.bz2 xenstore/
 
-install: xenstored libxenstore.a
+install: xenstored libxenstore.a xs_dom0_test
 	$(INSTALL_DIR) -p $(DESTDIR)/var/run/xenstored
 	$(INSTALL_DIR) -p $(DESTDIR)/var/lib/xenstored
 	$(INSTALL_DIR) -p $(DESTDIR)/usr/sbin
 	$(INSTALL_DIR) -p $(DESTDIR)/usr/include
 	$(INSTALL_PROG) xenstored $(DESTDIR)/usr/sbin
+	$(INSTALL_PROG) xs_dom0_test $(DESTDIR)/usr/sbin
 	$(INSTALL_DIR) -p $(DESTDIR)/usr/$(LIBDIR)
 	$(INSTALL_DATA) libxenstore.a $(DESTDIR)/usr/$(LIBDIR)
 	$(INSTALL_DATA) xs.h $(DESTDIR)/usr/include
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal xen/tools/xenstore/xs_dom0_test.c xen-dom0-store/tools/xenstore/xs_dom0_test.c
--- xen/tools/xenstore/xs_dom0_test.c	1970-01-01 10:00:00.000000000 +1000
+++ xen-dom0-store/tools/xenstore/xs_dom0_test.c	2005-06-16 16:51:00.000000000 +1000
@@ -0,0 +1,43 @@
+/* Test introduction of domain 0 */
+#include <linux/ioctl.h>
+#include <sys/ioctl.h>
+#include "xs.h"
+#include "utils.h"
+#include <xc.h>
+#include <xen/linux/privcmd.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+int main()
+{
+	int h, local = 0, kernel = 0;
+	long err;
+	void *page;
+
+	h = xc_interface_open();
+	if (h < 0)
+		barf_perror("Failed to open xc");
+
+	if (xc_evtchn_bind_interdomain(h, DOMID_SELF, 0, &local, &kernel) != 0)
+		barf_perror("Failed to bind interdomain");
+
+	printf("Got ports %i & %i\n", local, kernel);
+
+	err = ioctl(h, IOCTL_PRIVCMD_INITDOMAIN_STORE, kernel);
+	if (err < 0)
+		barf_perror("Failed to initialize store");
+	printf("Got mfn %li\n", err);
+
+	page = xc_map_foreign_range(h, 0, getpagesize(), PROT_READ|PROT_WRITE,
+				    err);
+	if (!page)
+		barf_perror("Failed to map page %li", err);
+	printf("Mapped page at %p\n", page);
+	printf("Page says %s\n", (char *)page);
+	munmap(page, getpagesize());
+	printf("unmapped\n");
+	
+	return 0;
+}
+	

-- 
A bad analogy is like a leaky screwdriver -- Richard Braakman