Hello Gerd, > -----Original Message----- > From: Qemu-devel > [mailto:qemu-devel-bounces+liqiang6-s=360...@nongnu.org] On Behalf Of > Gerd Hoffmann > Sent: Thursday, March 16, 2017 5:31 PM > To: qemu-devel@nongnu.org > Cc: Gerd Hoffmann > Subject: [Qemu-devel] [PULL for-2.9 4/7] cirrus: add option to disable blitter > > Ok, we have this beast in the cirrus code which is not used at all by modern > guests, except when you try to find security holes in qemu. So, add an option > to disable blitter altogether. Guests released within the last ten years > should > not show any rendering issues if you turn off blitter support. > > There are no known bugs in the cirrus blitter code. But in the past we hoped > a > few times already that we've finally nailed the last issue. So having some > easy > way to mitigate in case yet another blitter issue shows up certainly makes me > sleep a bit better at night. > > For completeness: The by far better way to mitigate is to switch away from > cirrus and use stdvga instead. Or something more modern like virtio-vga in > case your guest has support for it. > > Signed-off-by: Gerd Hoffmann <kra...@redhat.com> > Message-id: 1489494540-15745-1-git-send-email-kra...@redhat.com > --- > hw/display/cirrus_vga.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c index > 6ffe64f..326d511 100644 > --- a/hw/display/cirrus_vga.c > +++ b/hw/display/cirrus_vga.c > @@ -205,6 +205,7 @@ typedef struct CirrusVGAState { > uint32_t cirrus_bank_base[2]; > uint32_t cirrus_bank_limit[2]; > uint8_t cirrus_hidden_palette[48]; > + bool enable_blitter; > int cirrus_blt_pixelwidth; > int cirrus_blt_width; > int cirrus_blt_height; > @@ -960,6 +961,10 @@ static void cirrus_bitblt_start(CirrusVGAState * s) { > uint8_t blt_rop; > > + if (!s->enable_blitter) { > + goto bitblt_ignore; > + } > + > s->vga.gr[0x31] |= CIRRUS_BLT_BUSY; > > s->cirrus_blt_width = (s->vga.gr[0x20] | (s->vga.gr[0x21] << 8)) + 1; @@ > -3024,6 +3029,8 @@ static void isa_cirrus_vga_realizefn(DeviceState *dev, > Error **errp) static Property isa_cirrus_vga_properties[] = { > DEFINE_PROP_UINT32("vgamem_mb", struct ISACirrusVGAState, > cirrus_vga.vga.vram_size_mb, 4), > + DEFINE_PROP_BOOL("blitter", struct ISACirrusVGAState, > + cirrus_vga.enable_blitter, true), > DEFINE_PROP_END_OF_LIST(), > }; > > @@ -3093,6 +3100,8 @@ static void pci_cirrus_vga_realize(PCIDevice *dev, > Error **errp) static Property pci_vga_cirrus_properties[] = { > DEFINE_PROP_UINT32("vgamem_mb", struct PCICirrusVGAState, > cirrus_vga.vga.vram_size_mb, 4), > + DEFINE_PROP_BOOL("blitter", struct PCICirrusVGAState, > + cirrus_vga.enable_blitter, true),
The default is 'ENABLE'? I think there should be 'false'. Thanks. Qiang > DEFINE_PROP_END_OF_LIST(), > }; > > -- > 1.8.3.1 >
