Proposed changes to squash with previous patch --- multiple-monitors.rst | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/multiple-monitors.rst b/multiple-monitors.rst index 5967999..dd7a439 100644 --- a/multiple-monitors.rst +++ b/multiple-monitors.rst @@ -28,17 +28,18 @@ QXL driver supports multiple displays (up to 4) with a single video device, whereas the Windows QXL driver only supports a single display for each video device. So to enable 4 monitors, a Linux guest would need only a single QXL device, while a Windows guest would need to be configured with 4 separate QXL -devices. It is possible to limit the number of displays that a single linux -driver supports by setting the `qxl-vga.max_outputs` property in qemu. If you -are using libvirt to configure your guest, you may need to ensure that the -`heads` parameter for the video device is set properly. +devices. Since qemu 2.4.0, it is possible to limit the number of displays that +a single linux driver supports by setting the `qxl-vga.max_outputs`. If you are +using libvirt to configure your guest, you may need to ensure that the `heads` +parameter for the video device is set properly. QXL Driver Video Memory ----------------------- If you want to use multiple displays on your guest, you need to make sure that the device has enough video memory to support the number and size of screens -you intend to use. There are several QXL parameters that you can use to control -the amount of memory allocated to the QXL devices. These parameters are: +you intend to use. There are several QXL parameters in qemu that you can use to +control the amount of memory allocated to the QXL devices. These parameters +are: * `ram_size` / `ram_size_mb` * `vram_size` / `vram_size_mb` @@ -57,8 +58,8 @@ determines the size of the primary surface, and therefore determines the maximum resolution of the device. For devices that support multiple displays with a single device (i.e. Linux drivers), this primary surface must be large enough to contain all displays. This bar is also used for -dynamic meory such as cursors, commands, and images. The second bar is used for -offscreen memory. +dynamic memory such as cursors, commands, and images. The second bar is used +for offscreen memory. In KMS-based Linux drivers, all surfaces (including the primary surface) are allocated in the second memory bar and the first memory bar is used for dynamic @@ -66,8 +67,11 @@ memory such as cursors, commands, images, and monitor configs. Therefore, devices that support multiple displays will need larger values for `vram_size` / `vram_size_mb`. -XXX: what is `vram64_size_mb` used for? Does the non-KMS driver actually use -the second bar? +64 bit drivers support a larger second memory bar that can be configured with +`vram64_size_mb`. If `vram_size_mb` is configured to 32 and `vram64_size_mb` is +configured to 128, you will get a 32 bit memory bar of 32 megabytes and a 64 +bit memory bar of 128 megabytes. The first 32 megabytes of the 64 bit memory +bar will contain the same data as the 32 bit memory bar. Spice Protocol ++++++++++++++ @@ -91,7 +95,7 @@ As mentioned above, the Linux QXL device supports multiple displays in a single device, whereas the Windows QXL device requires a separate device for each display. This has implications at the protocol level as well. A Linux guest will have a single DisplayChannel which manages up to 4 displays on the same -channel. A Windows guest will have multiple DisplayChannels, one for each +channel. A Windows guest will have multiple Display channels, one for each device and each managing a single display. Implementation @@ -131,7 +135,7 @@ Older versions of the QXL driver do not provide the callback mentioned above and instead handle all monitor configuration changes via the spice-vdagent executable running within the guest. The configuration is sent from the host to the guest via the vdagent char device. The spice-vdagent executable then uses -platform APIs (e.g. xrandr on linux) to attempt to configure the displays to +platform APIs (e.g. xrandr on Linux) to attempt to configure the displays to match the requested configuration. Device implementation -- 2.9.3 _______________________________________________ Spice-devel mailing list Spice-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/spice-devel