[Qemu-devel] [PATCH] RFC: qxl: allow to specify head limit to qxl driver

[Frediano Ziglio <fziglio@redhat.com>]

This patch allow to limit number of heads using qxl driver. By default
qxl driver is not limited on any kind on head use so can decide to use
as much heads.

libvirt has this as a video card parameter (actually set to 1 but not
used). This parameter will allow to limit setting a use can do (which
could be confusing).

This patch rely on some change in spice-protocol which are not still
accepted. See
http://lists.freedesktop.org/archives/spice-devel/2015-June/020160.html.

Main question and stop over are parameter name. Consider that this
parameter is actually more a hint to drivers. I'm looking anyway to
a way to enforce this in spice-server.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
---
 hw/display/qxl.c | 6 ++++++
 hw/display/qxl.h | 1 +
 2 files changed, 7 insertions(+)

diff --git a/hw/display/qxl.c b/hw/display/qxl.c
index b220e2d..e9ccd30 100644
--- a/hw/display/qxl.c
+++ b/hw/display/qxl.c
@@ -327,6 +327,11 @@ static void init_qxl_rom(PCIQXLDevice *d)
     rom->log_level     = cpu_to_le32(d->guestdebug);
     rom->modes_offset  = cpu_to_le32(sizeof(QXLRom));
 
+    if (d->max_heads && d->max_heads <= 64) {
+        rom->flags         = cpu_to_le64(QXL_ROM_FLAG_MAX_HEADS);
+        rom->max_heads     = cpu_to_le16(d->max_heads);
+    }
+
     rom->slot_gen_bits = MEMSLOT_GENERATION_BITS;
     rom->slot_id_bits  = MEMSLOT_SLOT_BITS;
     rom->slots_start   = 1;
@@ -2278,6 +2283,7 @@ static Property qxl_properties[] = {
         DEFINE_PROP_UINT32("vram64_size_mb", PCIQXLDevice, vram_size_mb, -1),
         DEFINE_PROP_UINT32("vgamem_mb", PCIQXLDevice, vgamem_size_mb, 16),
         DEFINE_PROP_INT32("surfaces", PCIQXLDevice, ssd.num_surfaces, 1024),
+        DEFINE_PROP_UINT16("max_heads", PCIQXLDevice, max_heads, 0),
         DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/display/qxl.h b/hw/display/qxl.h
index deddd54..d785761 100644
--- a/hw/display/qxl.h
+++ b/hw/display/qxl.h
@@ -99,6 +99,7 @@ typedef struct PCIQXLDevice {
     QXLModes           *modes;
     uint32_t           rom_size;
     MemoryRegion       rom_bar;
+    uint16_t           max_heads;
 
     /* vram pci bar */
     uint32_t           vram_size;
-- 
2.1.0