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[Xen-devel] [PATCH for 4.5 v8 1/1] Add mmio_hole



If you add enough PCI devices then all mmio may not fit below 4G
which may not be the layout the user wanted. This allows you to
increase the below 4G address space that PCI devices can use and
therefore in more cases not have any mmio that is above 4G.

There are real PCI cards that do not support mmio over 4G, so if you
want to emulate them precisely, you may also need to increase the
space below 4G for them. There are drivers for these cards that also
do not work if they have their mmio space mapped above 4G.

This allows growing the MMIO hole to the size needed.

This may help with using pci passthru and HVM.

In the tools this is named mmio_hole_memkb.

Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
---
v8:
    Use MBYTES in xl.cfg
      Done.
    Use LOG().
      Done.
    Please make this a MemKB at the libxl interface level.
      Done -- s/mmio_hole_size/mmio_hole_memkb/ in tools/libxl/*
        s/mmio_hole_size/mmio_hole/ in docs/man/xl.cfg.pod.5 and
        tools/libxl/xl_cmdimpl.c
    Please drop Konrad's comment.
      Done.
    Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
      Did not add do changes to many parts.
      No change to tools/firmware/* so I think it still
        applies there.
    I am OK with this patch going in Xen 4.5 (as a release-manager).
      I think this is still applies.


v7:
    QEMU 2.1.0 reference confusing.
      Dropped.
    Why have assert(i < 9) & assert(i < 11)
      Dropped.
    This check for 256MB is surely obfuscated by the macros.
      Added comment to help.


v6:
  rebased.
    I think we should get rid of xc_hvm_build_with_hole() entirely.
      Done.
    Add text describing restrictions on hole size
      Done.
    "<=", to be consistent with the check in
        libxl__domain_create_info_setdefault ()
      Done

v5:
  Add LIBXL_HAVE_BUILDINFO_HVM_MMIO_HOLE_SIZE.

v4:
    s/pci_hole_min_size/mmio_hole_size/
    s/HVM_BELOW_4G_RAM_END/HVM_BELOW_4G_MMIO_START/
    Add ignore to hvmloader message
    Adjust commit message    
    Dropped min; stopped mmio_hole_size changing in hvmloader

 docs/man/xl.cfg.pod.5             | 15 +++++++++
 tools/firmware/hvmloader/config.h |  1 -
 tools/firmware/hvmloader/pci.c    | 71 +++++++++++++++++++++++++++------------
 tools/libxl/libxl.h               |  5 +++
 tools/libxl/libxl_create.c        | 29 ++++++++++++----
 tools/libxl/libxl_dm.c            | 20 +++++++++--
 tools/libxl/libxl_dom.c           |  8 +++++
 tools/libxl/libxl_types.idl       |  1 +
 tools/libxl/xl_cmdimpl.c          | 13 +++++++
 9 files changed, 132 insertions(+), 31 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index 5830e09..622ea53 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -1164,6 +1164,21 @@ wallclock (i.e., real) time.
 
 =back
 
+=head3 Memory layout
+
+=over 4
+
+=item B<mmio_hole=MBYTES>
+
+Specifies the size the MMIO hole below 4GiB will be.  Only valid for
+device_model_version = "qemu-xen".
+
+Cannot be smaller than 256. Cannot be larger than 3840.
+
+Known good large value is 3072.
+
+=back
+
 =head3 Support for Paravirtualisation of HVM Guests
 
 The following options allow Paravirtualised features (such as devices)
diff --git a/tools/firmware/hvmloader/config.h 
b/tools/firmware/hvmloader/config.h
index 80bea46..b838cf9 100644
--- a/tools/firmware/hvmloader/config.h
+++ b/tools/firmware/hvmloader/config.h
@@ -53,7 +53,6 @@ extern struct bios_config ovmf_config;
 #define PCI_ISA_IRQ_MASK    0x0c20U /* ISA IRQs 5,10,11 are PCI connected */
 
 /* MMIO hole: Hardcoded defaults, which can be dynamically expanded. */
-#define PCI_MEM_START       0xf0000000
 #define PCI_MEM_END         0xfc000000
 
 extern unsigned long pci_mem_start, pci_mem_end;
diff --git a/tools/firmware/hvmloader/pci.c b/tools/firmware/hvmloader/pci.c
index 3712988..4e8d803 100644
--- a/tools/firmware/hvmloader/pci.c
+++ b/tools/firmware/hvmloader/pci.c
@@ -28,9 +28,10 @@
 #include <xen/memory.h>
 #include <xen/hvm/ioreq.h>
 #include <xen/hvm/hvm_xs_strings.h>
+#include <xen/hvm/e820.h>
 #include <stdbool.h>
 
-unsigned long pci_mem_start = PCI_MEM_START;
+unsigned long pci_mem_start = HVM_BELOW_4G_MMIO_START;
 unsigned long pci_mem_end = PCI_MEM_END;
 uint64_t pci_hi_mem_start = 0, pci_hi_mem_end = 0;
 
@@ -59,6 +60,7 @@ void pci_setup(void)
         uint64_t bar_sz;
     } *bars = (struct bars *)scratch_start;
     unsigned int i, nr_bars = 0;
+    uint64_t mmio_hole_size = 0;
 
     const char *s;
     /*
@@ -86,6 +88,10 @@ void pci_setup(void)
     printf("Relocating guest memory for lowmem MMIO space %s\n",
            allow_memory_relocate?"enabled":"disabled");
 
+    s = xenstore_read("platform/mmio_hole_size", NULL);
+    if ( s )
+        mmio_hole_size = strtoll(s, NULL, 0);
+
     /* Program PCI-ISA bridge with appropriate link routes. */
     isa_irq = 0;
     for ( link = 0; link < 4; link++ )
@@ -237,26 +243,49 @@ void pci_setup(void)
         pci_writew(devfn, PCI_COMMAND, cmd);
     }
 
-    /*
-     * At the moment qemu-xen can't deal with relocated memory regions.
-     * It's too close to the release to make a proper fix; for now,
-     * only allow the MMIO hole to grow large enough to move guest memory
-     * if we're running qemu-traditional.  Items that don't fit will be
-     * relocated into the 64-bit address space.
-     *
-     * This loop now does the following:
-     * - If allow_memory_relocate, increase the MMIO hole until it's
-     *   big enough, or until it's 2GiB
-     * - If !allow_memory_relocate, increase the MMIO hole until it's
-     *   big enough, or until it's 2GiB, or until it overlaps guest
-     *   memory
-     */
-    while ( (mmio_total > (pci_mem_end - pci_mem_start)) 
-            && ((pci_mem_start << 1) != 0)
-            && (allow_memory_relocate
-                || (((pci_mem_start << 1) >> PAGE_SHIFT)
-                    >= hvm_info->low_mem_pgend)) )
-        pci_mem_start <<= 1;
+    if ( mmio_hole_size )
+    {
+        uint64_t max_ram_below_4g = (1ULL << 32) - mmio_hole_size;
+
+        if ( max_ram_below_4g > HVM_BELOW_4G_MMIO_START )
+        {
+            printf("max_ram_below_4g=0x"PRIllx
+                   " too big for mmio_hole_size=0x"PRIllx
+                   " has been ignored.\n",
+                   PRIllx_arg(max_ram_below_4g),
+                   PRIllx_arg(mmio_hole_size));
+        }
+        else
+        {
+            pci_mem_start = max_ram_below_4g;
+            printf("pci_mem_start=0x%lx (was 0x%x) for mmio_hole_size=%lu\n",
+                   pci_mem_start, HVM_BELOW_4G_MMIO_START,
+                   (long)mmio_hole_size);
+        }
+    }
+    else
+    {
+        /*
+         * At the moment qemu-xen can't deal with relocated memory regions.
+         * It's too close to the release to make a proper fix; for now,
+         * only allow the MMIO hole to grow large enough to move guest memory
+         * if we're running qemu-traditional.  Items that don't fit will be
+         * relocated into the 64-bit address space.
+         *
+         * This loop now does the following:
+         * - If allow_memory_relocate, increase the MMIO hole until it's
+         *   big enough, or until it's 2GiB
+         * - If !allow_memory_relocate, increase the MMIO hole until it's
+         *   big enough, or until it's 2GiB, or until it overlaps guest
+         *   memory
+         */
+        while ( (mmio_total > (pci_mem_end - pci_mem_start))
+                && ((pci_mem_start << 1) != 0)
+                && (allow_memory_relocate
+                    || (((pci_mem_start << 1) >> PAGE_SHIFT)
+                        >= hvm_info->low_mem_pgend)) )
+            pci_mem_start <<= 1;
+    }
 
     if ( mmio_total > (pci_mem_end - pci_mem_start) )
     {
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 28b614f..c3451bd 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -158,6 +158,11 @@
 #define LIBXL_BUILDINFO_HVM_VIRIDIAN_ENABLE_DISABLE_WIDTH 64
 
 /*
+ * libxl_domain_build_info has the u.hvm.mmio_hole_memkb field.
+ */
+#define LIBXL_HAVE_BUILDINFO_HVM_MMIO_HOLE_MEMKB 1
+
+/*
  * libxl ABI compatibility
  *
  * The only guarantee which libxl makes regarding ABI compatibility
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 4b33d07..b1ff5ae 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -23,6 +23,7 @@
 #include <xc_dom.h>
 #include <xenguest.h>
 #include <xen/hvm/hvm_info_table.h>
+#include <xen/hvm/e820.h>
 
 int libxl__domain_create_info_setdefault(libxl__gc *gc,
                                          libxl_domain_create_info *c_info)
@@ -226,6 +227,8 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
     case LIBXL_DOMAIN_TYPE_HVM:
         if (b_info->shadow_memkb == LIBXL_MEMKB_DEFAULT)
             b_info->shadow_memkb = 0;
+        if (b_info->u.hvm.mmio_hole_memkb == LIBXL_MEMKB_DEFAULT)
+            b_info->u.hvm.mmio_hole_memkb = 0;
 
         if (!b_info->u.hvm.vga.kind)
             b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
@@ -429,13 +432,25 @@ int libxl__domain_build(libxl__gc *gc,
         vments[4] = "start_time";
         vments[5] = libxl__sprintf(gc, "%lu.%02d", 
start_time.tv_sec,(int)start_time.tv_usec/10000);
 
-        localents = libxl__calloc(gc, 7, sizeof(char *));
-        localents[0] = "platform/acpi";
-        localents[1] = libxl_defbool_val(info->u.hvm.acpi) ? "1" : "0";
-        localents[2] = "platform/acpi_s3";
-        localents[3] = libxl_defbool_val(info->u.hvm.acpi_s3) ? "1" : "0";
-        localents[4] = "platform/acpi_s4";
-        localents[5] = libxl_defbool_val(info->u.hvm.acpi_s4) ? "1" : "0";
+        localents = libxl__calloc(gc, 9, sizeof(char *));
+        i = 0;
+        localents[i++] = "platform/acpi";
+        localents[i++] = libxl_defbool_val(info->u.hvm.acpi) ? "1" : "0";
+        localents[i++] = "platform/acpi_s3";
+        localents[i++] = libxl_defbool_val(info->u.hvm.acpi_s3) ? "1" : "0";
+        localents[i++] = "platform/acpi_s4";
+        localents[i++] = libxl_defbool_val(info->u.hvm.acpi_s4) ? "1" : "0";
+        if (info->u.hvm.mmio_hole_memkb) {
+            uint64_t max_ram_below_4g =
+                (1ULL << 32) - (info->u.hvm.mmio_hole_memkb << 10);
+
+            if (max_ram_below_4g <= HVM_BELOW_4G_MMIO_START) {
+                localents[i++] = "platform/mmio_hole_size";
+                localents[i++] =
+                    libxl__sprintf(gc, "%"PRIu64,
+                                   info->u.hvm.mmio_hole_memkb << 10);
+            }
+        }
 
         break;
     case LIBXL_DOMAIN_TYPE_PV:
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 14dc9fa..3e191c3 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -18,6 +18,7 @@
 #include "libxl_osdeps.h" /* must come before any other headers */
 
 #include "libxl_internal.h"
+#include <xen/hvm/e820.h>
 
 static const char *libxl_tapif_script(libxl__gc *gc)
 {
@@ -416,6 +417,7 @@ static char ** libxl__build_device_model_args_new(libxl__gc 
*gc,
     const libxl_vnc_info *vnc = libxl__dm_vnc(guest_config);
     const libxl_sdl_info *sdl = dm_sdl(guest_config);
     const char *keymap = dm_keymap(guest_config);
+    char *machinearg;
     flexarray_t *dm_args;
     int i, connection, devid;
     uint64_t ram_size;
@@ -720,10 +722,24 @@ static char ** 
libxl__build_device_model_args_new(libxl__gc *gc,
             /* Switching here to the machine "pc" which does not add
              * the xen-platform device instead of the default "xenfv" machine.
              */
-            flexarray_append(dm_args, "pc,accel=xen");
+            machinearg = libxl__sprintf(gc, "pc,accel=xen");
         } else {
-            flexarray_append(dm_args, "xenfv");
+            machinearg = libxl__sprintf(gc, "xenfv");
         }
+        if (b_info->u.hvm.mmio_hole_memkb) {
+            uint64_t max_ram_below_4g = (1ULL << 32) -
+                (b_info->u.hvm.mmio_hole_memkb << 10);
+
+            if (max_ram_below_4g > HVM_BELOW_4G_MMIO_START) {
+                LOG(WARN, "mmio_hole_memkb=%"PRIu64
+                    " invalid ignored.\n",
+                    b_info->u.hvm.mmio_hole_memkb);
+            } else {
+                machinearg = libxl__sprintf(gc, "%s,max-ram-below-4g=%"PRIu64,
+                                            machinearg, max_ram_below_4g);
+            }
+        }
+        flexarray_append(dm_args, machinearg);
         for (i = 0; b_info->extra_hvm && b_info->extra_hvm[i] != NULL; i++)
             flexarray_append(dm_args, b_info->extra_hvm[i]);
         break;
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 9d830e1..74ea84b 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -23,6 +23,7 @@
 #include <xc_dom.h>
 #include <xen/hvm/hvm_info_table.h>
 #include <xen/hvm/hvm_xs_strings.h>
+#include <xen/hvm/e820.h>
 
 libxl_domain_type libxl__domain_type(libxl__gc *gc, uint32_t domid)
 {
@@ -800,6 +801,13 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
     args.mem_size = (uint64_t)(info->max_memkb - info->video_memkb) << 10;
     args.mem_target = (uint64_t)(info->target_memkb - info->video_memkb) << 10;
     args.claim_enabled = libxl_defbool_val(info->claim_mode);
+    if (info->u.hvm.mmio_hole_memkb) {
+        uint64_t max_ram_below_4g = (1ULL << 32) -
+            (info->u.hvm.mmio_hole_memkb << 10);
+
+        if (max_ram_below_4g < HVM_BELOW_4G_MMIO_START)
+            args.mmio_size = info->u.hvm.mmio_hole_memkb << 10;
+    }
     if (libxl__domain_firmware(gc, info, &args)) {
         LOG(ERROR, "initializing domain firmware failed");
         goto out;
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index fdda761..ca3f724 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -413,6 +413,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                        ("timeoffset",       string),
                                        ("hpet",             libxl_defbool),
                                        ("vpt_align",        libxl_defbool),
+                                       ("mmio_hole_memkb",  MemKB),
                                        ("timer_mode",       libxl_timer_mode),
                                        ("nested_hvm",       libxl_defbool),
                                        ("smbios_firmware",  string),
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index ea43761..9a88750 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -34,6 +34,7 @@
 #include <ctype.h>
 #include <inttypes.h>
 #include <limits.h>
+#include <xen/hvm/e820.h>
 
 #include "libxl.h"
 #include "libxl_utils.h"
@@ -1191,6 +1192,18 @@ static void parse_config_data(const char *config_source,
             exit(-ERROR_FAIL);
         }
 
+        if (!xlu_cfg_get_long(config, "mmio_hole", &l, 0)) {
+            uint64_t mmio_hole_size;
+
+            b_info->u.hvm.mmio_hole_memkb = l * 1024;
+            mmio_hole_size = b_info->u.hvm.mmio_hole_memkb * 1024;
+            if (mmio_hole_size < HVM_BELOW_4G_MMIO_LENGTH ||
+                mmio_hole_size > HVM_BELOW_4G_MMIO_START) {
+                fprintf(stderr, "ERROR: invalid value %"PRIu64
+                        " for \"mmio_hole\"\n", l);
+                exit (1);
+            }
+        }
         if (!xlu_cfg_get_long(config, "timer_mode", &l, 1)) {
             const char *s = libxl_timer_mode_to_string(l);
             fprintf(stderr, "WARNING: specifying \"timer_mode\" as an integer 
is deprecated. "
-- 
1.8.4


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