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Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt
From: |
Andrew Jones |
Subject: |
Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer |
Date: |
Tue, 19 Jan 2016 13:37:16 +0100 |
User-agent: |
Mutt/1.5.23.1 (2014-03-12) |
On Tue, Jan 19, 2016 at 12:49:18PM +0100, Christoffer Dall wrote:
> The virt board has an arch timer, which is always on. Emit the
> "always-on" property to indicate to Linux that it can switch off the
> periodic timer and reduces the amount of interrupts injected into a
> guest.
>
> Signed-off-by: Christoffer Dall <address@hidden>
> ---
> hw/arm/virt.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 05f9087..265fe9a 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -291,6 +291,7 @@ static void fdt_add_timer_nodes(const VirtBoardInfo *vbi,
> int gictype)
> qemu_fdt_setprop_string(vbi->fdt, "/timer", "compatible",
> "arm,armv7-timer");
> }
> + qemu_fdt_setprop(vbi->fdt, "/timer", "always-on", NULL, 0);
> qemu_fdt_setprop_cells(vbi->fdt, "/timer", "interrupts",
> GIC_FDT_IRQ_TYPE_PPI, ARCH_TIMER_S_EL1_IRQ, irqflags,
> GIC_FDT_IRQ_TYPE_PPI, ARCH_TIMER_NS_EL1_IRQ, irqflags,
> --
> 2.1.2.330.g565301e.dirty
>
>
Hi Christoffer,
We should also patch the ACPI generation at the same time. I think
something like
- gtdt->non_secure_el1_flags = ACPI_EDGE_SENSITIVE;
+ gtdt->non_secure_el1_flags = ACPI_EDGE_SENSITIVE | ACPI_GTDT_ALWAYS_ON;
should do it.
Also, having the guest reduce the number of interrupts sounds good. Can
you point me to something to read about how/why a guest may choose to do
that, and what the trade-offs are?
Thanks,
drew
- [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Christoffer Dall, 2016/01/19
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer,
Andrew Jones <=
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Christoffer Dall, 2016/01/19
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Andrew Jones, 2016/01/19
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Marc Zyngier, 2016/01/19
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Andrew Jones, 2016/01/19
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Andrew Jones, 2016/01/19
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Andrew Jones, 2016/01/20
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Marc Zyngier, 2016/01/20
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Andrew Jones, 2016/01/20
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Marc Zyngier, 2016/01/20
- Re: [Qemu-devel] [PATCH] hw/arm/virt: Add always-on property to the virt board timer, Andrew Jones, 2016/01/20