Re: [Qemu-arm] [PATCH] virt-acpi-build: add always-on property for timer

[Shannon Zhao <zhaoshenglong@huawei.com>]

On 2016/1/21 20:54, Andrew Jones wrote:
> This patch is the ACPI equivalent of "hw/arm/virt: Add always-on
> property to the virt board timer". The timer is always on, and
> thus setting this informs Linux that it may switch off the periodic
> timer. Switching off the periodic timer substantially reduces the
> number of interrupts the host needs to inject.
> 
> Testing note: AArch64 guests (the only ones currently booting with
> ACPI) do not actually need this patch to determine it can turn the
> periodic timer off. I therefore used a hacked guest kernel to ensure
> this patch works as the equivalent DT patch does.
> 
Reviewed-by: Shannon Zhao <shannon.zhao@linaro.org>

> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
>  hw/arm/virt-acpi-build.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 87fbe7c97d99b..f6e538f3d02ea 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -443,7 +443,7 @@ build_gtdt(GArray *table_data, GArray *linker)
>      gtdt->secure_el1_flags = ACPI_EDGE_SENSITIVE;
>  
>      gtdt->non_secure_el1_interrupt = ARCH_TIMER_NS_EL1_IRQ + 16;
> -    gtdt->non_secure_el1_flags = ACPI_EDGE_SENSITIVE;
> +    gtdt->non_secure_el1_flags = ACPI_EDGE_SENSITIVE | ACPI_GTDT_ALWAYS_ON;
>  
>      gtdt->virtual_timer_interrupt = ARCH_TIMER_VIRT_IRQ + 16;
>      gtdt->virtual_timer_flags = ACPI_EDGE_SENSITIVE;
> 

-- 
Shannon