>
> When the QXL driver receives a QXL_INTERRUPT_CLIENT_MONITORS_CONFIG
> interrupt,
> we currently always notify userspace that there was some hotplug event.
>
> However, gnome-shell/mutter is reacting to this event by attempting a
> resolution change, which it does by issueing drmModeRmFB, drmModeAddFB,
> and then drmModeSetCrtc. This has the side-effect of causing
> qxl_crtc_mode_set() to tell the QXL virtual hardware that a primary
> surface was destroyed and created. After going through QEMU and then the
> remote SPICE client, a new identical monitors config message will be
> sent, resulting in a QXL_INTERRUPT_CLIENT_MONITORS_CONFIG interrupt to
> be emitted, and the same scenario occurring again.
>
> As destroying/creating the primary surface causes a visible screen
> flicker, this makes the guest hard to use (
> https://bugzilla.redhat.com/show_bug.cgi?id=1266484 ).
>
> This commit checks if the screen configuration we received is the same
> one as the current one, and does not notify userspace about it if that's
> the case.
>
> Signed-off-by: Christophe Fergeau <cfergeau at redhat.com>
Great message!
> ---
> drivers/gpu/drm/qxl/qxl_display.c | 65
> +++++++++++++++++++++++++++++++++------
> 1 file changed, 55 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/qxl/qxl_display.c
> b/drivers/gpu/drm/qxl/qxl_display.c
> index 156b7de..edb90f6 100644
> --- a/drivers/gpu/drm/qxl/qxl_display.c
> +++ b/drivers/gpu/drm/qxl/qxl_display.c
> @@ -57,11 +57,18 @@ static void qxl_alloc_client_monitors_config(struct
> qxl_device *qdev, unsigned c
> qdev->client_monitors_config->count = count;
> }
>
> +enum MonitorsConfigCopyStatus {
> + MONITORS_CONFIG_COPIED,
> + MONITORS_CONFIG_UNCHANGED,
> + MONITORS_CONFIG_BAD_CRC,
> +};
> +
I don't remember exactly kernel style, a
typedef enum {
MONITORS_CONFIG_COPIED,
MONITORS_CONFIG_UNCHANGED,
MONITORS_CONFIG_BAD_CRC,
} MonitorsConfigCopyStatus;
could make following code shorter.
> static int qxl_display_copy_rom_client_monitors_config(struct qxl_device
> *qdev)
why not returning MonitorsConfigCopyStatus ?
> {
> int i;
> int num_monitors;
> uint32_t crc;
> + bool changed = false;
>
using a "MonitorsConfigCopyStatus res = MONITORS_CONFIG_UNCHANGED" here
could make return statement shorter.
> num_monitors = qdev->rom->client_monitors_config.count;
> crc = crc32(0, (const uint8_t *)&qdev->rom->client_monitors_config,
> @@ -70,7 +77,7 @@ static int
> qxl_display_copy_rom_client_monitors_config(struct qxl_device *qdev)
> qxl_io_log(qdev, "crc mismatch: have %X (%zd) != %X\n", crc,
> sizeof(qdev->rom->client_monitors_config),
> qdev->rom->client_monitors_config_crc);
> - return 1;
> + return MONITORS_CONFIG_BAD_CRC;
> }
> if (num_monitors > qdev->monitors_config->max_allowed) {
> DRM_DEBUG_KMS("client monitors list will be truncated: %d <
> %d\n",
> @@ -79,6 +86,10 @@ static int
> qxl_display_copy_rom_client_monitors_config(struct qxl_device *qdev)
> } else {
> num_monitors = qdev->rom->client_monitors_config.count;
> }
> + if (qdev->client_monitors_config
> + && (num_monitors != qdev->client_monitors_config->count)) {
> + changed = true;
> + }
> qxl_alloc_client_monitors_config(qdev, num_monitors);
> /* we copy max from the client but it isn't used */
> qdev->client_monitors_config->max_allowed =
> @@ -88,17 +99,42 @@ static int
> qxl_display_copy_rom_client_monitors_config(struct qxl_device *qdev)
> &qdev->rom->client_monitors_config.heads[i];
> struct qxl_head *client_head =
> &qdev->client_monitors_config->heads[i];
> - client_head->x = c_rect->left;
> - client_head->y = c_rect->top;
> - client_head->width = c_rect->right - c_rect->left;
> - client_head->height = c_rect->bottom - c_rect->top;
> - client_head->surface_id = 0;
> - client_head->id = i;
> - client_head->flags = 0;
> + if (client_head->x != c_rect->left) {
> + client_head->x = c_rect->left;
> + changed = true;
> + }
> + if (client_head->y != c_rect->top) {
> + client_head->y = c_rect->top;
> + changed = true;
> + }
> + if (client_head->width != c_rect->right - c_rect->left) {
> + client_head->width = c_rect->right - c_rect->left;
> + changed = true;
> + }
> + if (client_head->height != c_rect->bottom - c_rect->top) {
> + client_head->height = c_rect->bottom - c_rect->top;
> + changed = true;
> + }
> + if (client_head->surface_id != 0) {
> + client_head->surface_id = 0;
> + changed = true;
> + }
> + if (client_head->id != i) {
> + client_head->id = i;
> + changed = true;
> + }
quite similar code... I would write a macro but I'm a too macro fun :)
Would be something like this
if (client_head->id != i)
res = MONITORS_CONFIG_COPIED;
client_head->id = i;
make sense?
> + if (client_head->flags != 0) {
> + client_head->flags = 0;
> + changed = true;
> + }
why testing flags change if is always 0 ?
> DRM_DEBUG_KMS("read %dx%d+%d+%d\n", client_head->width,
> client_head->height,
> client_head->x, client_head->y);
> }
> - return 0;
> + if (changed) {
> + return MONITORS_CONFIG_COPIED;
> + } else {
> + return MONITORS_CONFIG_UNCHANGED;
> + }
Here it would be just "return res;".
> }
>
> static void qxl_update_offset_props(struct qxl_device *qdev)
> @@ -124,9 +160,18 @@ void qxl_display_read_client_monitors_config(struct
> qxl_device *qdev)
> {
>
> struct drm_device *dev = qdev->ddev;
> - while (qxl_display_copy_rom_client_monitors_config(qdev)) {
> + enum MonitorsConfigCopyStatus status;
> +
> + status = qxl_display_copy_rom_client_monitors_config(qdev);
> + while (status == MONITORS_CONFIG_BAD_CRC) {
> qxl_io_log(qdev, "failed crc check for client_monitors_config,"
> " retrying\n");
> + status = qxl_display_copy_rom_client_monitors_config(qdev);
> + }
Usually I would write something like
for (;;) {
status = qxl_display_copy_rom_client_monitors_config(qdev);
if (status != MONITORS_CONFIG_BAD_CRC)
break;
qxl_io_log(qdev, "failed crc check for client_monitors_config,"
" retrying\n");
}
or
while ((status = qxl_display_copy_rom_client_monitors_config(qdev))
== MONITORS_CONFIG_BAD_CRC) {
qxl_io_log(qdev, "failed crc check for client_monitors_config,"
" retrying\n");
}
(just style and probably indentation is even wrong)
> + if (status == MONITORS_CONFIG_UNCHANGED) {
> + qxl_io_log(qdev, "config unchanged\n");
> + DRM_DEBUG("ignoring unchanged client monitors config");
> + return;
> }
>
> drm_modeset_lock_all(dev);
Beside all that style paranoia/opinions:
Acked-by: Frediano Ziglio <fziglio at redhat.com>
(feel free to take into account some or none of them).
Frediano
