[Qemu-devel] [PATCH v2] xen_console: support the new extended xenstore protocol

[Qemu-devel] [PATCH v2] xen_console: support the new extended xenstore protocol

[stefano.stabellini]

From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

Since CS 21994 on xen-unstable.hg and CS
466608f3a32e1f9808acdf832a5843af37e5fcec on qemu-xen-unstable.git, few
changes have been introduced to the PV console xenstore protocol, as
described by the document docs/misc/console.txt under xen-unstable.hg.

>From the Qemu point of view, very few modifications are needed to
correctly support the protocol: read from xenstore the "output" node
that tell us what the output of the PV console is going to be.
In case the output is a tty, write to xenstore the device name.

Changes in v2:

- fix error paths: free malloc'ed strings and close the xenstore
connection before returning;

- remove useless snprintf in xenstore_store_pv_console_info if i == 0.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 hw/xen.h         |    1 +
 hw/xen_console.c |   16 +++++++++-----
 xen-all.c        |   60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+), 6 deletions(-)

diff --git a/hw/xen.h b/hw/xen.h
index d435ca0..dad0ca0 100644
--- a/hw/xen.h
+++ b/hw/xen.h
@@ -50,6 +50,7 @@ qemu_irq *xen_interrupt_controller_init(void);
 int xen_init(void);
 int xen_hvm_init(void);
 void xen_vcpu_init(void);
+void xenstore_store_pv_console_info(int i, struct CharDriverState *chr);
 
 #if defined(NEED_CPU_H) && !defined(CONFIG_USER_ONLY)
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size);
diff --git a/hw/xen_console.c b/hw/xen_console.c
index 519d5f5..e81afcd 100644
--- a/hw/xen_console.c
+++ b/hw/xen_console.c
@@ -179,8 +179,9 @@ static void xencons_send(struct XenConsole *con)
 static int con_init(struct XenDevice *xendev)
 {
     struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);
-    char *type, *dom;
+    char *type, *dom, label[32];
     int ret = 0;
+    const char *output;
 
     /* setup */
     dom = xs_get_domain_path(xenstore, con->xendev.dom);
@@ -194,11 +195,14 @@ static int con_init(struct XenDevice *xendev)
         goto out;
     }
 
-    if (!serial_hds[con->xendev.dev])
-	xen_be_printf(xendev, 1, "WARNING: serial line %d not configured\n",
-                      con->xendev.dev);
-    else
-        con->chr = serial_hds[con->xendev.dev];
+    output = xenstore_read_str(con->console, "output");
+    /* output is a pty by default */
+    if (output == NULL) {
+        output = "pty";
+    }
+    snprintf(label, sizeof(label), "xencons%d", con->xendev.dev);
+    con->chr = qemu_chr_open(label, output, NULL);
+    xenstore_store_pv_console_info(con->xendev.dev, con->chr);
 
 out:
     qemu_free(type);
diff --git a/xen-all.c b/xen-all.c
index 6099bff..3f8aadb 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -737,6 +737,66 @@ static void cpu_handle_ioreq(void *opaque)
     }
 }
 
+static int store_dev_info(int domid, CharDriverState *cs, const char *string)
+{
+    struct xs_handle *xs = NULL;
+    char *path = NULL;
+    char *newpath = NULL;
+    char *pts = NULL;
+    int ret = -1;
+
+    /* Only continue if we're talking to a pty. */
+    if (strncmp(cs->filename, "pty:", 4)) {
+        return 0;
+    }
+    pts = cs->filename + 4;
+
+    /* We now have everything we need to set the xenstore entry. */
+    xs = xs_daemon_open();
+    if (xs == NULL) {
+        fprintf(stderr, "Could not contact XenStore\n");
+        goto out;
+    }
+
+    path = xs_get_domain_path(xs, domid);
+    if (path == NULL) {
+        fprintf(stderr, "xs_get_domain_path() error\n");
+        goto out;
+    }
+    newpath = realloc(path, (strlen(path) + strlen(string) +
+                strlen("/tty") + 1));
+    if (newpath == NULL) {
+        fprintf(stderr, "realloc error\n");
+        goto out;
+    }
+    path = newpath;
+
+    strcat(path, string);
+    strcat(path, "/tty");
+    if (!xs_write(xs, XBT_NULL, path, pts, strlen(pts))) {
+        fprintf(stderr, "xs_write for '%s' fail", string);
+        goto out;
+    }
+    ret = 0;
+
+out:
+    free(path);
+    xs_daemon_close(xs);
+
+    return ret;
+}
+
+void xenstore_store_pv_console_info(int i, CharDriverState *chr)
+{
+    if (i == 0) {
+        store_dev_info(xen_domid, chr, "/console");
+    } else {
+        char buf[32];
+        snprintf(buf, sizeof(buf), "/device/console/%d", i);
+        store_dev_info(xen_domid, chr, buf);
+    }
+}
+
 static void xenstore_record_dm_state(XenIOState *s, const char *state)
 {
     char path[50];
-- 
1.7.2.3

Re: [Qemu-devel] [PATCH v2] xen_console: support the new extended xenstore protocol

[Peter Maydell]

On 28 June 2011 15:55,  <stefano.stabellini@eu.citrix.com> wrote:
> +    xs = xs_daemon_open();
> +    if (xs == NULL) {
> +        fprintf(stderr, "Could not contact XenStore\n");
> +        goto out;
> +    }

> +out:
> +    free(path);
> +    xs_daemon_close(xs);

Google suggests xs_daemon_close(NULL) will crash...

-- PMM

Re: [Qemu-devel] [Xen-devel] Re: [PATCH v2] xen_console: support the new extended xenstore protocol

[Ian Campbell]

On Tue, 2011-06-28 at 16:02 +0100, Peter Maydell wrote:
> On 28 June 2011 15:55,  <stefano.stabellini@eu.citrix.com> wrote:
> > +    xs = xs_daemon_open();
> > +    if (xs == NULL) {
> > +        fprintf(stderr, "Could not contact XenStore\n");
> > +        goto out;
> > +    }
> 
> > +out:
> > +    free(path);
> > +    xs_daemon_close(xs);
> 
> Google suggests xs_daemon_close(NULL) will crash...

Also the preferred interface these days is just xs_open/close. The other
variants are deprecated.

Ian.

Re: [Qemu-devel] [Xen-devel] Re: [PATCH v2] xen_console: support the new extended xenstore protocol

[Stefano Stabellini]

On Tue, 28 Jun 2011, Ian Campbell wrote:
> On Tue, 2011-06-28 at 16:02 +0100, Peter Maydell wrote:
> > On 28 June 2011 15:55,  <stefano.stabellini@eu.citrix.com> wrote:
> > > +    xs = xs_daemon_open();
> > > +    if (xs == NULL) {
> > > +        fprintf(stderr, "Could not contact XenStore\n");
> > > +        goto out;
> > > +    }
> > 
> > > +out:
> > > +    free(path);
> > > +    xs_daemon_close(xs);
> > 
> > Google suggests xs_daemon_close(NULL) will crash...
> 
> Also the preferred interface these days is just xs_open/close. The other
> variants are deprecated.

And xs_close doesn't crash if the parameter is NULL, so it will kill two
birds with one stone.