PV console for HVM domains

Creates a shared memory ring buffer and event channel in HVM domains
for passing debug messages from PV drivers on HVM guests
The console is used by windows pv drivers to send debug data to xenconsoled

Signed-off-by: Owen Smith <owen.smith@citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

tools/libxc/xc_domain_restore.c

@@ -640,6 +640,7 @@ typedef struct {
     uint64_t vcpumap;
     uint64_t identpt;
     uint64_t vm86_tss;
+    uint64_t console_pfn;
 } pagebuf_t;
 
 static int pagebuf_init(pagebuf_t* buf)
@@ -737,6 +738,16 @@ static int pagebuf_get_one(xc_interface *xch, struct restore_ctx *ctx,
             return -1;
         }
         return pagebuf_get_one(xch, ctx, buf, fd, dom);
+    } else if (count == -8 ) {
+        /* Skip padding 4 bytes then read the console pfn location. */
+        if ( read_exact(fd, &buf->console_pfn, sizeof(uint32_t)) ||
+             read_exact(fd, &buf->console_pfn, sizeof(uint64_t)) )
+        {
+            PERROR("error read the address of the console pfn");
+            return -1;
+        }
+        // DPRINTF("console pfn location: %llx\n", buf->console_pfn);
+        return pagebuf_get_one(xch, ctx, buf, fd, dom);
     } else if ( (count > MAX_BATCH_SIZE) || (count < 0) ) {
         ERROR("Max batch size exceeded (%d). Giving up.", count);
         errno = EMSGSIZE;
@@ -1055,6 +1066,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
     pagebuf_t pagebuf;
     tailbuf_t tailbuf, tmptail;
     void* vcpup;
+    uint64_t console_pfn = 0;
 
     static struct restore_ctx _ctx = {
         .live_p2m = NULL,
@@ -1207,6 +1219,8 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
                 xc_set_hvm_param(xch, dom, HVM_PARAM_IDENT_PT, pagebuf.identpt);
             if ( pagebuf.vm86_tss )
                 xc_set_hvm_param(xch, dom, HVM_PARAM_VM86_TSS, pagebuf.vm86_tss);
+            if ( pagebuf.console_pfn )
+                console_pfn = pagebuf.console_pfn;
             break;  /* our work here is done */
         }
 
@@ -1717,6 +1731,19 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
     }
     *store_mfn = tailbuf.u.hvm.magicpfns[2];
 
+    if ( console_pfn ) {
+        if ( xc_clear_domain_page(xch, dom, console_pfn) ) {
+            PERROR("error zeroing console page");
+            goto out;
+        }
+        if ( (frc = xc_set_hvm_param(xch, dom, 
+                                    HVM_PARAM_CONSOLE_PFN, console_pfn)) ) {
+            PERROR("error setting HVM param: %i", frc);
+            goto out;
+        }
+        *console_mfn = console_pfn;
+    }
+
     frc = xc_domain_hvm_setcontext(xch, dom, tailbuf.u.hvm.hvmbuf,
                                    tailbuf.u.hvm.reclen);
     if ( frc )

tools/libxc/xc_domain_save.c

@@ -1587,6 +1587,17 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
             PERROR("Error when writing the vm86 TSS for guest");
             goto out;
         }
+
+        chunk.id = -8;
+        xc_get_hvm_param(xch, dom, HVM_PARAM_CONSOLE_PFN,
+                         (unsigned long *)&chunk.data);
+
+        if ( (chunk.data != 0) &&
+             wrexact(io_fd, &chunk, sizeof(chunk)) )
+        {
+            PERROR("Error when writing the console pfn for guest");
+            goto out;
+        }
     }
 
     /* Zero terminate */

tools/libxc/xc_hvm_build.c

@@ -28,7 +28,8 @@
 #define SPECIALPAGE_XENSTORE 1
 #define SPECIALPAGE_IOREQ    2
 #define SPECIALPAGE_IDENT_PT 3
-#define NR_SPECIAL_PAGES     4
+#define SPECIALPAGE_CONSOLE  4
+#define NR_SPECIAL_PAGES     5
 #define special_pfn(x) (0xff000u - NR_SPECIAL_PAGES + (x))
 
 static void build_hvm_info(void *hvm_info_page, uint64_t mem_size)
@@ -354,6 +355,8 @@ static int setup_guest(xc_interface *xch,
                      special_pfn(SPECIALPAGE_BUFIOREQ));
     xc_set_hvm_param(xch, dom, HVM_PARAM_IOREQ_PFN,
                      special_pfn(SPECIALPAGE_IOREQ));
+    xc_set_hvm_param(xch, dom, HVM_PARAM_CONSOLE_PFN,
+                     special_pfn(SPECIALPAGE_CONSOLE));
 
     /*
      * Identity-map page table is required for running with CR0.PG=0 when

tools/libxl/libxl_dom.c

@@ -237,7 +237,7 @@ int build_hvm(libxl_ctx *ctx, uint32_t domid,
         return ERROR_FAIL;
     }
     ret = hvm_build_set_params(ctx->xch, domid, info, state->store_port,
-                               &state->store_mfn);
+                               &state->store_mfn, state->console_port, &state->console_mfn);
     if (ret) {
         XL_LOG_ERRNOVAL(ctx, XL_LOG_ERROR, ret, "hvm build set params failed");
         return ERROR_FAIL;

tools/libxl/libxl_internal.h

@@ -173,7 +173,8 @@ int libxl_device_pci_reset(libxl_ctx *ctx, unsigned int domain, unsigned int bus
 /* from xenguest (helper */
 int hvm_build_set_params(xc_interface *handle, uint32_t domid,
                          libxl_domain_build_info *info,
-                         int store_evtchn, unsigned long *store_mfn);
+                         int store_evtchn, unsigned long *store_mfn,
+                         int console_evtchn, unsigned long *console_mfn);
 
 /* xl_exec */
 

tools/libxl/xenguest.c

@@ -23,7 +23,8 @@
 
 int hvm_build_set_params(xc_interface *handle, uint32_t domid,
                          libxl_domain_build_info *info,
-                         int store_evtchn, unsigned long *store_mfn)
+                         int store_evtchn, unsigned long *store_mfn,
+                         int console_evtchn, unsigned long *console_mfn)
 {
     struct hvm_info_table *va_hvm;
     uint8_t *va_map, sum;
@@ -46,6 +47,7 @@ int hvm_build_set_params(xc_interface *handle, uint32_t domid,
     munmap(va_map, XC_PAGE_SIZE);
 
     xc_get_hvm_param(handle, domid, HVM_PARAM_STORE_PFN, store_mfn);
+    xc_get_hvm_param(handle, domid, HVM_PARAM_CONSOLE_PFN, console_mfn);
     xc_set_hvm_param(handle, domid, HVM_PARAM_PAE_ENABLED, info->u.hvm.pae);
 #if defined(__i386__) || defined(__x86_64__)
     xc_set_hvm_param(handle, domid, HVM_PARAM_VIRIDIAN, info->u.hvm.viridian);
@@ -54,5 +56,6 @@ int hvm_build_set_params(xc_interface *handle, uint32_t domid,
     xc_set_hvm_param(handle, domid, HVM_PARAM_TIMER_MODE, (unsigned long) info->u.hvm.timer_mode);
     xc_set_hvm_param(handle, domid, HVM_PARAM_VPT_ALIGN, (unsigned long) info->u.hvm.vpt_align);
     xc_set_hvm_param(handle, domid, HVM_PARAM_STORE_EVTCHN, store_evtchn);
+    xc_set_hvm_param(handle, domid, HVM_PARAM_CONSOLE_EVTCHN, console_evtchn);
     return 0;
 }

tools/libxl/xl_cmdimpl.c

@@ -1433,6 +1433,9 @@ start:
         }
     }
     if (d_config.c_info.hvm) {
+        init_console_info(&console, 0, &state);
+        console.domid = domid;
+        libxl_device_console_add(&ctx, domid, &console);
         dm_info.domid = domid;
         MUST( libxl_create_device_model(&ctx, &dm_info,
                                         d_config.disks, d_config.num_disks,

xen/include/public/hvm/params.h

@@ -109,6 +109,10 @@
 /* Boolean: Enable aligning all periodic vpts to reduce interrupts */
 #define HVM_PARAM_VPT_ALIGN    16
 
-#define HVM_NR_PARAMS          17
+/* Console debug shared memory ring and event channel */
+#define HVM_PARAM_CONSOLE_PFN    17
+#define HVM_PARAM_CONSOLE_EVTCHN 18
+
+#define HVM_NR_PARAMS          19
 
 #endif /* __XEN_PUBLIC_HVM_PARAMS_H__ */