linux-kernel - Re: [PATCH] clocksource/arm_arch_timer: Store physical timer IRQ number for KVM on VHE

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Date:   Tue, 12 Feb 2019 10:15:22 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Christoffer Dall <christoffer.dall@....com>,
        linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        Andre Przywara <andre.przywara@....com>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH] clocksource/arm_arch_timer: Store physical timer IRQ
 number for KVM on VHE

On 24/01/2019 14:46, Christoffer Dall wrote:
> From: Andre Przywara <andre.przywara@....com>
> 
> A host running in VHE mode gets the EL2 physical timer as its time
> source (accessed using the EL1 sysreg accessors, which get re-directed
> to the EL2 sysregs by VHE).
> 
> The EL1 physical timer remains unused by the host kernel, allowing us to
> pass that on directly to a KVM guest and saves us from emulating this
> timer for the guest on VHE systems.
> 
> Store the EL1 Physical Timer's IRQ number in
> struct arch_timer_kvm_info on VHE systems to allow KVM to use it.
> 
> Signed-off-by: Andre Przywara <andre.przywara@....com>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> Signed-off-by: Christoffer Dall <christoffer.dall@....com>
> ---
> Patches in preparation for nested virtualization on KVM/Arm depend on this
> change, so we would like to merge this via the kvmarm tree or have a stable
> branch including this patch.
> 
> Please let us know your preference.  Thanks.

Hi Christopher,

sorry for the delay. I'm fine if you want to take it through your tree.

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>



>  drivers/clocksource/arm_arch_timer.c | 11 +++++++++--
>  include/clocksource/arm_arch_timer.h |  1 +
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 9a7d4dc00b6e..b9243e2328b4 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -1206,6 +1206,13 @@ static enum arch_timer_ppi_nr __init arch_timer_select_ppi(void)
>  	return ARCH_TIMER_PHYS_SECURE_PPI;
>  }
>  
> +static void __init arch_timer_populate_kvm_info(void)
> +{
> +	arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];
> +	if (is_kernel_in_hyp_mode())
> +		arch_timer_kvm_info.physical_irq = arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI];
> +}
> +
>  static int __init arch_timer_of_init(struct device_node *np)
>  {
>  	int i, ret;
> @@ -1220,7 +1227,7 @@ static int __init arch_timer_of_init(struct device_node *np)
>  	for (i = ARCH_TIMER_PHYS_SECURE_PPI; i < ARCH_TIMER_MAX_TIMER_PPI; i++)
>  		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
>  
> -	arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];
> +	arch_timer_populate_kvm_info();
>  
>  	rate = arch_timer_get_cntfrq();
>  	arch_timer_of_configure_rate(rate, np);
> @@ -1550,7 +1557,7 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
>  	arch_timer_ppi[ARCH_TIMER_HYP_PPI] =
>  		acpi_gtdt_map_ppi(ARCH_TIMER_HYP_PPI);
>  
> -	arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];
> +	arch_timer_populate_kvm_info();
>  
>  	/*
>  	 * When probing via ACPI, we have no mechanism to override the sysreg
> diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
> index 349e5957c949..702967d996bb 100644
> --- a/include/clocksource/arm_arch_timer.h
> +++ b/include/clocksource/arm_arch_timer.h
> @@ -74,6 +74,7 @@ enum arch_timer_spi_nr {
>  struct arch_timer_kvm_info {
>  	struct timecounter timecounter;
>  	int virtual_irq;
> +	int physical_irq;
>  };
>  
>  struct arch_timer_mem_frame {
> 


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