Increase DATA_LIMIT to 64 KiB

handler_port.c

@@ -49,31 +49,56 @@ static struct {
 static void
 io_port_writel(uint64_t offset, uint64_t size, uint32_t val)
 {
-    xen_pfn_t pfns[SHMEM_PAGES];
+    xen_pfn_t pfns[SHMEM_PAGES_V2_MAX];
     void *shmem;
+    UINT32 version, nr_pages;
+    enum command_t command;
     int i;
+    uint8_t *ptr;
+    EFI_STATUS status;
 
     if (offset != 0 || size != sizeof(uint32_t)) {
         DBG("Expected size 4, offset 0.  Got %" PRIu64 ", %" PRIu64 ".\n", size, offset);
         return;
     }
 
-    for (i = 0; i < SHMEM_PAGES; i++)
+    for (i = 0; i < SHMEM_PAGES_V2_MAX; i++)
         pfns[i] = val + i;
     DBG("io_port write\n");
 
+    /* Only the first page is wanted for nr_pages detection */
     shmem = xenforeignmemory_map(io_info.fmem,
                                  io_info.domid,
                                  PROT_READ | PROT_WRITE,
-                                 SHMEM_PAGES, pfns, NULL);
+                                 1, pfns, NULL);
+    if (!shmem) {
+        DBG("map foreign range failed (snoop): %d\n", errno);
+        return;
+    }
+
+    ptr = shmem;
+    /* nr_pages is the only thing we're interested in here */
+    status = snoop_command(&ptr, &version, &nr_pages, &command);
+
+    xenforeignmemory_unmap(io_info.fmem, shmem, 1);
+
+    if (status != EFI_SUCCESS) {
+        DBG("snoop_command refused version data\n");
+        return;
+    }
+
+    shmem = xenforeignmemory_map(io_info.fmem,
+                                 io_info.domid,
+                                 PROT_READ | PROT_WRITE,
+                                 nr_pages, pfns, NULL);
     if (!shmem) {
         DBG("map foreign range failed: %d\n", errno);
         return;
     }
 
-    dispatch_command(shmem);
+    dispatch_snooped_command(shmem, version, nr_pages, command);
 
-    xenforeignmemory_unmap(io_info.fmem, shmem, SHMEM_PAGES);
+    xenforeignmemory_unmap(io_info.fmem, shmem, nr_pages);
 
 }
 
@@ -85,4 +110,3 @@ setup_handler_io_port(domid_t domid, xenforeignmemory_handle *fmem) {
 
     return register_io_port_writel_handler(HANDLER_PORT_ADDRESS, io_port_writel);
 }
-

include/handler.h

@@ -34,9 +34,41 @@
 
 #include "efi.h"
 
+#define PAGE_SIZE 4096
+#define SHMEM_PAGES_V1 16
+/* Consumers shouldn't use this value, but should stick to SHMEM_PAGES_V2_MAX */
+#define SHMEM_PAGES_V2_MIN 18
+#define SHMEM_PAGES_V2_MAX 32
+
 #define NAME_LIMIT 4096 /* Maximum length of name */
-#define DATA_LIMIT 57344 /* Maximum length of a single variable */
-#define TOTAL_LIMIT 131072 /* Maximum total storage */
+
+/*
+ * Maximum length of a single variable. To ensure that there's sufficient room
+ * for variables in the communication buffer, SHMEM_PAGES must be high enough to
+ * cover the data limit + 1 page (4096 bytes) for the variable name + 1 page for
+ * protocol overhead.
+ */
+#define DATA_LIMIT(shmem_pages) (((shmem_pages) - 2) * PAGE_SIZE)
+
+/* The following limits must respect the minimum prescribed by WHCP. */
+
+#define DATA_LIMIT_V1 DATA_LIMIT(SHMEM_PAGES_V1)
+/*
+ * For now, DATA_LIMIT_V2 and SHMEM_PAGES_V2_MIN are coupled: DATA_LIMIT_V2 is
+ * calculated from SHMEM_PAGES_V2_MIN, and one can't be increased without
+ * increasing the other.
+ *
+ * However, there's reserved headroom in SHMEM_PAGES_V2_MAX for later silently
+ * increasing DATA_LIMIT_V2; consumers should  stick to SHMEM_PAGES_V2_MAX and
+ * not worry about this.
+ */
+#define DATA_LIMIT_V2 DATA_LIMIT(SHMEM_PAGES_V2_MIN)
+
+/* For non-protocol uses */
+#define DATA_LIMIT_MAX DATA_LIMIT_V2
+
+/* Maximum total storage */
+#define TOTAL_LIMIT 131072
 
 /*
  * A single variable takes up a minimum number of bytes.
@@ -46,10 +78,6 @@
 #define VARIABLE_SIZE_OVERHEAD 128
 #define MAX_VARIABLE_COUNT (TOTAL_LIMIT / VARIABLE_SIZE_OVERHEAD)
 
-#define PAGE_SIZE 4096
-#define SHMEM_PAGES 16
-#define SHMEM_SIZE (SHMEM_PAGES * PAGE_SIZE)
-
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
 
 enum command_t {
@@ -74,6 +102,13 @@ struct efi_variable {
 
 extern struct efi_variable *var_list;
 
+UINTN data_limit(UINT32 version);
+EFI_STATUS snoop_command(uint8_t **comm_buf, UINT32 *out_version,
+                         UINT32 *out_nr_pages, enum command_t *out_command);
+void skip_command(uint8_t **comm_buf, UINT32 version, UINT32 nr_pages,
+                  enum command_t command);
+void dispatch_snooped_command(uint8_t *comm_buf, UINT32 version, UINT32 nr_pages,
+                              enum command_t command);
 void dispatch_command(uint8_t *comm_buf);
 bool setup_crypto(void);
 bool setup_variables(void);