On 10 September 2014 12:43, Christoffer Dall <christoffer.d...@linaro.org> wrote: > On Tue, Sep 09, 2014 at 03:53:43PM +0100, Peter Maydell wrote: >> The pl011 and pl031 devices both use level triggered interrupts, >> but the device tree we construct was incorrectly telling the >> kernel to configure the GIC to treat them as edge triggered. >> This meant that output from the pl011 would hang after a while. >> >> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> >> Cc: qemu-sta...@nongnu.org >> --- >> Thanks to Christoffer Dall for figuring out the cause of the hangs here. >> >> hw/arm/virt.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/hw/arm/virt.c b/hw/arm/virt.c >> index e8f231e..1b343f0 100644 >> --- a/hw/arm/virt.c >> +++ b/hw/arm/virt.c >> @@ -371,7 +371,7 @@ static void create_uart(const VirtBoardInfo *vbi, >> qemu_irq *pic) >> 2, base, 2, size); >> qemu_fdt_setprop_cells(vbi->fdt, nodename, "interrupts", >> GIC_FDT_IRQ_TYPE_SPI, irq, >> - GIC_FDT_IRQ_FLAGS_EDGE_LO_HI); >> + GIC_FDT_IRQ_FLAGS_LEVEL_HI); >> qemu_fdt_setprop_cells(vbi->fdt, nodename, "clocks", >> vbi->clock_phandle, vbi->clock_phandle); >> qemu_fdt_setprop(vbi->fdt, nodename, "clock-names", >> @@ -398,7 +398,7 @@ static void create_rtc(const VirtBoardInfo *vbi, >> qemu_irq *pic) >> 2, base, 2, size); >> qemu_fdt_setprop_cells(vbi->fdt, nodename, "interrupts", >> GIC_FDT_IRQ_TYPE_SPI, irq, >> - GIC_FDT_IRQ_FLAGS_EDGE_LO_HI); >> + GIC_FDT_IRQ_FLAGS_LEVEL_HI); >> qemu_fdt_setprop_cell(vbi->fdt, nodename, "clocks", vbi->clock_phandle); >> qemu_fdt_setprop_string(vbi->fdt, nodename, "clock-names", "apb_pclk"); >> g_free(nodename); >> -- >> 1.9.1 >> > I've been trying to figure out why we would see this particular hang > with SMP and not UP (or maybe it is just very much more unlikely to > happen with UP), but haven't been able to come up with a sequence of > events to support this yet. It also worries me that we weren't seeing > this with KVM, since it indicates that we're either doing something > wrong in the KVM or QEMU GIC emulation code, potentially. > > In any case, this patch is correct, so: > > Acked-by: Christoffer Dall <christoffer.d...@linaro.org>
I am still seeing lockups and self detected stalls even with this patch, and sometimes just hitting a key into the console will get things moving again. So I am not convinced yet whether this fixes something fundamentally, or just works around it by taking an alternative code path through the kernel which doesn't trigger the same root bug.
