From: Wei Hu <[email protected]> Sent: Tuesday, August 27, 2019 4:25 AM > > Without deferred IO support, hyperv_fb driver informs the host to refresh > the entire guest frame buffer at fixed rate, e.g. at 20Hz, no matter there > is screen update or not. This patch supports deferred IO for screens in > graphics mode and also enables the frame buffer on-demand refresh. The > highest refresh rate is still set at 20Hz. > > Currently Hyper-V only takes a physical address from guest as the starting > address of frame buffer. This implies the guest must allocate contiguous > physical memory for frame buffer. In addition, Hyper-V Gen 2 VMs only > accept address from MMIO region as frame buffer address. Due to these > limitations on Hyper-V host, we keep a shadow copy of frame buffer > in the guest. This means one more copy of the dirty rectangle inside > guest when doing the on-demand refresh. This can be optimized in the > future with help from host. For now the host performance gain from deferred > IO outweighs the shadow copy impact in the guest. > > v2: Incorporated review comments from Michael Kelley > - Increased dirty rectangle by one row in deferred IO case when sending > to Hyper-V. > - Corrected the dirty rectangle size in the text mode. > - Added more comments. > - Other minor code cleanups.
Version history should go after the "---" below so it is not included in the commit message. > > Signed-off-by: Wei Hu <[email protected]> > --- > drivers/video/fbdev/Kconfig | 1 + > drivers/video/fbdev/hyperv_fb.c | 221 +++++++++++++++++++++++++++++--- > 2 files changed, 202 insertions(+), 20 deletions(-) > > +/* Deferred IO callback */ > +static void synthvid_deferred_io(struct fb_info *p, > + struct list_head *pagelist) > +{ > + struct hvfb_par *par = p->par; > + struct page *page; > + unsigned long start, end; > + int y1, y2, miny, maxy; > + unsigned long flags; > + > + miny = INT_MAX; > + maxy = 0; > + > + /* > + * Merge dirty pages. It is possible that last page cross > + * over the end of frame buffer row yres. This is taken care of > + * in synthvid_update function by clamping the y2 > + * value to yres. > + */ > + list_for_each_entry(page, pagelist, lru) { > + start = page->index << PAGE_SHIFT; > + end = start + PAGE_SIZE - 1; > + y1 = start / p->fix.line_length; > + y2 = end / p->fix.line_length; > + if (y2 > p->var.yres) > + y2 = p->var.yres; The above test seems contradictory to the comment that says the clamping is done in synthvid_update(). Also, since the above calculation of y2 is "inclusive", the clamping should be done to yres - 1 in order to continue to be inclusive. Then when maxy + 1 is passed to synthvid_update() everything works out correctly. > + miny = min_t(int, miny, y1); > + maxy = max_t(int, maxy, y2); > + > + /* Copy from dio space to mmio address */ > + if (par->fb_ready) { > + spin_lock_irqsave(&par->docopy_lock, flags); > + hvfb_docopy(par, start, PAGE_SIZE); > + spin_unlock_irqrestore(&par->docopy_lock, flags); > + } > + } > + > + if (par->fb_ready) > + synthvid_update(p, 0, miny, p->var.xres, maxy + 1); > +} > + > +static struct fb_deferred_io synthvid_defio = { > + .delay = HZ / 20, > + .deferred_io = synthvid_deferred_io, > +}; > > /* > * Actions on received messages from host: > @@ -604,7 +683,7 @@ static int synthvid_send_config(struct hv_device *hdev) > msg->vid_hdr.type = SYNTHVID_VRAM_LOCATION; > msg->vid_hdr.size = sizeof(struct synthvid_msg_hdr) + > sizeof(struct synthvid_vram_location); > - msg->vram.user_ctx = msg->vram.vram_gpa = info->fix.smem_start; > + msg->vram.user_ctx = msg->vram.vram_gpa = par->mmio_pp; > msg->vram.is_vram_gpa_specified = 1; > synthvid_send(hdev, msg); > > @@ -614,7 +693,7 @@ static int synthvid_send_config(struct hv_device *hdev) > ret = -ETIMEDOUT; > goto out; > } > - if (msg->vram_ack.user_ctx != info->fix.smem_start) { > + if (msg->vram_ack.user_ctx != par->mmio_pp) { > pr_err("Unable to set VRAM location\n"); > ret = -ENODEV; > goto out; > @@ -631,19 +710,82 @@ static int synthvid_send_config(struct hv_device *hdev) > > /* > * Delayed work callback: > - * It is called at HVFB_UPDATE_DELAY or longer time interval to process > - * screen updates. It is re-scheduled if further update is necessary. > + * It is scheduled to call whenever update request is received and it has > + * not been called in last HVFB_ONDEMAND_THROTTLE time interval. > */ > static void hvfb_update_work(struct work_struct *w) > { > struct hvfb_par *par = container_of(w, struct hvfb_par, dwork.work); > struct fb_info *info = par->info; > + unsigned long flags; > + int x1, x2, y1, y2; > + int j; > + > + spin_lock_irqsave(&par->delayed_refresh_lock, flags); > + /* Reset the request flag */ > + par->delayed_refresh = false; > + > + /* Store the dirty rectangle to local variables */ > + x1 = par->x1; > + x2 = par->x2; > + y1 = par->y1; > + y2 = par->y2; > + > + /* Clear dirty rectangle */ > + par->x1 = par->y1 = INT_MAX; > + par->x2 = par->y2 = 0; > + > + spin_unlock_irqrestore(&par->delayed_refresh_lock, flags); > > + if (x1 < 0 || x1 > info->var.xres || x2 < 0 || > + x2 > info->var.xres || y1 < 0 || y1 > info->var.yres || > + y2 < 0 || y2 > info->var.yres || x2 <= x1) > + return; Are the tests for less than 0 needed? I think all possibility of negative values has been eliminated. > + > + /* Copy the dirty rectangle to frame buffer memory */ > + spin_lock_irqsave(&par->docopy_lock, flags); > + for (j = y1; j < y2; j++) { > + if (j == info->var.yres) > + break; The above test isn't needed. The maximum value that y2 can be is yres (that is checked a few lines above in the big "if" statement). Since j is always less than y2, j can never be equal to yres. > + hvfb_docopy(par, > + j * info->fix.line_length + > + (x1 * screen_depth / 8), > + (x2 - x1) * screen_depth / 8); > + } > + spin_unlock_irqrestore(&par->docopy_lock, flags); > + > + /* Refresh */ > if (par->fb_ready) > - synthvid_update(info); > + synthvid_update(info, x1, y1, x2, y2); > +} > + Michael
