on some modern machines like the x250, the bios arranges the mtrr's
and the framebuffer membar in a way that doesnt allow us to mark
the framebuffer pages as write combining, leading to slow graphics.
since the pentium III, the processor interprets the page table bit
combinations of the WT, CD and bit7 bits as an index into the
page attribute table (PAT).
to not change the semantics of the WT and CD bits, we preserve
the bit patterns 0-3 and use the last entry 7 for write combining.
(done in mmuinit() for each core).
the new patwc() function takes virtual address range and changes
the page table marking the range as write combining. no attempt
is made on invalidating tlb's. doesnt matter in our case as the
following mtrr() call in screen.c does it for us.
introduce cpushutdown() function that does the common
operation of initiating shutdown, returning once all
cpu's got the message and are about to shutdown. this
avoids duplicated code which isnt really machine specific.
automatic reboot on panic only when *debug= is not set
and the machine is a cpu server or has no display,
otherwise just hang.
add bootscreenconf(VGAscr *) function, that is called whenever
the framebuffer configuration is changed by devvga. that way, we
can pass the current setting of the framebuffer to the new
kernel when using /dev/reboot.
we have to reset hwblank when switching drivers to
prevent the generic vgablank() to be called by
blankscreen().
remove code setting hwblank from vga drivers as
devvga will always force hwblank to be 1 or 0
depending on if the driver provides a native blanking
routine.
set hwaccel to 1 when the driver provides native fill
and scroll routines independent of softscreen being
disabled. this allows hw acceleration to be used when
softscreen gets switched off.
to make it possible to mark the bootscreen framebuffer
as write combining in early initialization, mtrr() is
changed not not to error() but to return an error string.
as bootscreen() is used before multiprocessor initialization,
we have to synchronize the mtrr's for every processor as
it comes online. for this, a new mtrrsync() function is
provided that is called from cpuidentify() if mtrr support
is indicated.
the boot processor runs mtrrsync() which snarfs the
registers. later, mtrrsync() is run again from the
application processors which apply the values from the
boot processor.
checkmtrr() from mp.c was removed as its task is also
done by mtrrsync() now.
the vmware svga video card emulated by qemu (qemu -vga vmware) complains and eventually causes a panic if the rectangles aren't clipped.
messages like the following can be observed from qemu before the kernel panics:
vmsvga_update_rect: update h was < 0 (-20000)
vmsvga_update_rect: update height too large y: 10000, h: 0
vmsvga_update_rect: update w was < 0 (-20000)
vmsvga_update_rect: update width too large x: 10000, w: 0
i could only reproduce this in qemu 2.0.50 on the master branch, when using the ui and had selected 'Zoom To Fit' from the View menu.
the software cursor starts flickering and reacts bumby if a process
spends most of its time with drawlock acquired because the timer interrupt
thats supposed to redraw the cursor fails to acquire the lock at the time
the timer fires.
instead of trying to draw the cursor on the screen from a timer interrupt
30 times per second, devmouse now creates a process calling cursoron() and
cursoroff() when the cursor needs to be redrawn. this allows the swcursor
to schedule a redraw while holding the drawlock in swcursoravoid() and
cursoron()/cursoroff() are now able to wait for a qlock (drawlock) because
they get called from process context.
the overall responsiveness is also improved with this change as the cursor
redraw rate isnt limited to 30 times a second anymore.
previously, we had to maintain 3 sets of pci vid/did's:
1) in /lib/vgadb for detection
2) in the userspace driver in aux/vga
3) in the kernel mode driver
this change makes the kernel mode driver more dumb in
the cases where possible. we let userspace do the pci
enumeration and if needed, it can set the pci address
of the vga card. kernel mode drivers can assume to get
the right pci device passed in scr->pci for enable()
and linear() functions and just do very basic sanity
checking before mapping framebuffer and mmio regions.
vgalinearpciid() was removed as userspace is responsible
to pick pci device.
theres a new vgactl message "pcidev" where userspace
can set the bus address. we initialize scr->pci in
vgareset() to the first pci graphics card found. this
should cover cases when an old aux/vga binary is used
that doesnt use the new pcidev message.
userspace drivers will now use the pci device that got
a match from /lib/vgadb and skip ther own enumeration.
this way, vga cards can be made to work by simply adding
an entry in vgadb with no need to modify userspace or
kernelspace drivers. this is not always possible if
the driver derives information from the specific card
model.
allow the shadow framebuffer (softscreen) to be used with any
vga driver, not just vesa. this removes the ugly scr->paddr = 0
hack employed by vesa driver to force softscreen and adds a
softscreen vgactl message that can switch the feature on and off
at runtime.
softscreen can greatly improve graphics performance when bus
reads are slow even tho it disables hardware acceleration.
