hvmloader: Add a xenbus frontend so it can read values from xenstore

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>

tools/firmware/hvmloader/Makefile

@@ -29,7 +29,7 @@ LOADADDR = 0x100000
 CFLAGS += $(CFLAGS_include) -I.
 
 SRCS  = hvmloader.c mp_tables.c util.c smbios.c 
-SRCS += 32bitbios_support.c smp.c cacheattr.c
+SRCS += 32bitbios_support.c smp.c cacheattr.c xenbus.c
 ifeq ($(debug),y)
 SRCS += tests.c
 endif

tools/firmware/hvmloader/hvmloader.c

@@ -704,6 +704,7 @@ int main(void)
 
     printf("CPU speed is %u MHz\n", get_cpu_mhz());
 
+    xenbus_setup();
     apic_setup();
     pci_setup();
 
@@ -803,6 +804,8 @@ int main(void)
     bios_info->madt_lapic0_addr = madt_lapic0_addr;
     bios_info->bios32_entry = bios32_addr;
 
+    xenbus_shutdown();
+
     printf("Invoking ROMBIOS ...\n");
     return 0;
 }

tools/firmware/hvmloader/util.h

@@ -155,6 +155,18 @@ int vprintf(const char *fmt, va_list ap);
 void *mem_alloc(uint32_t size, uint32_t align);
 #define virt_to_phys(v) ((unsigned long)(v))
 
+/* Connect our xenbus client to the backend.  
+ * Call once, before any other xenbus actions. */
+void xenbus_setup(void);
+
+/* Reset the xenbus connection so the next kernel can start again. */
+void xenbus_shutdown(void);
+
+/* Read a xenstore key.  Returns a nul-terminated string (even if the XS
+ * data wasn't nul-terminated) or NULL.  The returned string is in a
+ * static buffer, so only valid until the next xenstore/xenbus operation. */
+char *xenstore_read(char *path);
+
 /* Prepare the 32bit BIOS */
 uint32_t highbios_setup(void);
 

tools/firmware/hvmloader/xenbus.c

@@ -0,0 +1,200 @@
+/*
+ * xenbus.c: static, synchronous, read-only xenbus client for hvmloader.
+ *
+ * Copyright (c) 2009 Tim Deegan, Citrix Systems (R&D) Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "util.h"
+#include "hypercall.h"
+#include <errno.h>
+#include <xen/sched.h>
+#include <xen/event_channel.h>
+#include <xen/hvm/params.h>
+#include <xen/io/xs_wire.h>
+
+struct xenstore_domain_interface *rings; /* Shared ring with dom0 */
+evtchn_port_t event;                     /* Event-channel to dom0 */
+char payload[XENSTORE_PAYLOAD_MAX + 1];  /* Unmarshalling area */
+
+/* Connect our xenbus client to the backend.
+ * Call once, before any other xenbus actions. */
+void xenbus_setup(void)
+{
+    xen_hvm_param_t param;
+
+    /* Ask Xen where the xenbus shared page is. */
+    param.domid = DOMID_SELF;
+    param.index = HVM_PARAM_STORE_PFN;
+    if ( hypercall_hvm_op(HVMOP_get_param, &param) )
+        BUG();
+    rings = (void *) (unsigned long) (param.value << PAGE_SHIFT);
+
+    /* Ask Xen where the xenbus event channel is. */
+    param.domid = DOMID_SELF;
+    param.index = HVM_PARAM_STORE_EVTCHN;
+    if ( hypercall_hvm_op(HVMOP_get_param, &param) )
+        BUG();
+    event = param.value;
+
+    printf("Xenbus rings @0x%lx, event channel %lu\n",
+           (unsigned long) rings, (unsigned long) event);
+}
+
+/* Reset the xenbus connection so the next kernel can start again. 
+ * We zero out the whole ring -- the backend can handle this, and it's 
+ * not going to surprise any frontends since it's equivalent to never 
+ * having used the rings. */
+void xenbus_shutdown(void)
+{
+    ASSERT(rings != NULL);
+    memset(rings, 0, sizeof *rings);
+    rings = NULL;
+}
+
+/* Helper functions: copy data in and out of the ring */
+static void ring_write(char *data, uint32_t len)
+{
+    uint32_t part;
+
+    ASSERT(len <= XENSTORE_PAYLOAD_MAX);
+
+    while ( len )
+    {
+        /* Don't overrun the consumer pointer */
+        part = (XENSTORE_RING_SIZE - 1) -
+            MASK_XENSTORE_IDX(rings->req_prod - rings->req_cons);
+        /* Don't overrun the end of the ring */
+        if ( part > (XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->req_prod)) )
+            part = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->req_prod);
+        /* Don't write more than we were asked for */
+        if ( part > len ) 
+            part = len;
+
+        memcpy(rings->req + MASK_XENSTORE_IDX(rings->req_prod), data, part);
+        barrier(); /* = wmb before prod write, rmb before next cons read */
+        rings->req_prod += part;
+        len -= part;
+
+        if ( len )
+            hypercall_sched_op(SCHEDOP_yield, NULL);
+    }
+}
+
+static void ring_read(char *data, uint32_t len)
+{
+    uint32_t part;
+
+    ASSERT(len <= XENSTORE_PAYLOAD_MAX);
+
+    while ( len )
+    {
+        /* Don't overrun the producer pointer */
+        part = MASK_XENSTORE_IDX(rings->rsp_prod - rings->rsp_cons);
+        /* Don't overrun the end of the ring */
+        if ( part > (XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->rsp_cons)) )
+            part = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->rsp_cons);
+        /* Don't read more than we were asked for */
+        if ( part > len )
+            part = len;
+
+        memcpy(data, rings->rsp + MASK_XENSTORE_IDX(rings->rsp_cons), part);
+        barrier(); /* = wmb before cons write, rmb before next prod read */
+        rings->rsp_cons += part;
+        len -= part;
+        
+        if ( len )
+            hypercall_sched_op(SCHEDOP_yield, NULL);
+    }
+}
+
+
+/* Send a request and wait for the answer.
+ * Returns 0 for success, or an errno for error.
+ * The answer is returned in a static buffer which is only
+ * valid until the next call of xenbus_send(). */
+static int xenbus_send(uint32_t type, uint32_t len, char *data,
+                       uint32_t *reply_len, char **reply_data)
+{
+    struct xsd_sockmsg hdr;
+    evtchn_send_t send;
+    int i;
+
+    /* Not acceptable to use xenbus before setting it up */
+    ASSERT(rings != NULL);
+
+    /* Put the request on the ring */
+    hdr.type = type;
+    hdr.req_id = 0;  /* We only ever issue one request at a time */
+    hdr.tx_id = 0;   /* We never use transactions */
+    hdr.len = len;
+    ring_write((char *) &hdr, sizeof hdr);
+    ring_write(data, len);
+
+    /* Tell the other end about the request */
+    send.port = event;
+    hypercall_event_channel_op(EVTCHNOP_send, &send);
+
+    /* Properly we should poll the event channel now but that involves
+     * mapping the shared-info page and handling the bitmaps. */
+
+    /* Pull the reply off the ring */
+    ring_read((char *) &hdr, sizeof(hdr));
+    ring_read(payload, hdr.len);
+    /* For sanity's sake, nul-terminate the answer */
+    payload[hdr.len] = '\0';
+
+    /* Handle errors */
+    if ( hdr.type == XS_ERROR )
+    {
+        *reply_len = 0;
+        for ( i = 0; i < ((sizeof xsd_errors) / (sizeof xsd_errors[0])); i++ )
+            if ( !strcmp(xsd_errors[i].errstring, payload) )
+                return xsd_errors[i].errnum;
+        /* Default error value if we couldn't decode the ASCII error */
+        return EIO;
+    }
+
+    *reply_data = payload;
+    *reply_len = hdr.len;
+    return 0;
+}
+
+
+/* Read a xenstore key.  Returns a nul-terminated string (even if the XS
+ * data wasn't nul-terminated) or NULL.  The returned string is in a
+ * static buffer, so only valid until the next xenstore/xenbus operation. */
+char *xenstore_read(char *path)
+{
+    uint32_t len = 0;
+    char *answer = NULL;
+
+    /* Include the nul in the request */
+    if ( xenbus_send(XS_READ, strlen(path) + 1, path, &len, &answer) )
+        return NULL;
+    /* We know xenbus_send() nul-terminates its answer, so just pass it on. */
+    return answer;
+}
+
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */