linux-kernel - Re: [PATCH v3 6/6] kvm: arm64: Add ACPI support for virt arch timer

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Message-ID: <56B8CBE8.7020305@arm.com>
Date:	Mon, 8 Feb 2016 17:10:00 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	fu.wei@...aro.org, rjw@...ysocki.net, lenb@...nel.org,
	daniel.lezcano@...aro.org, tglx@...utronix.de,
	christoffer.dall@...aro.org, gleb@...nel.org, pbonzini@...hat.com,
	hanjun.guo@...aro.org, wei@...hat.com,
	a.spyridakis@...tualopensystems.com
Cc:	linaro-acpi@...ts.linaro.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
	al.stone@...aro.org, graeme.gregory@...aro.org,
	davem@...emloft.net, jeffrey.t.kirsher@...el.com,
	richardcochran@...il.com, arnd@...db.de, wim@...ana.be,
	jcm@...hat.com, leo.duran@....com, mark.rutland@....com,
	catalin.marinas@....com, will.deacon@....com,
	Suravee.Suthikulpanit@....com, robherring2@...il.com
Subject: Re: [PATCH v3 6/6] kvm: arm64: Add ACPI support for virt arch timer

On 01/02/16 20:26, fu.wei@...aro.org wrote:
> From: Fu Wei <fu.wei@...aro.org>
> 
> This patch adds ACPI/GTDT support for virt arch timer
> using the API in GTDT driver.
> 
> Signed-off-by: Fu Wei <fu.wei@...aro.org>
> ---
>  virt/kvm/arm/arch_timer.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 0a279d3..4077347 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -385,6 +385,9 @@ static int kvm_timer_get_ppi(unsigned int *ppi)
>  {
>  	struct device_node *np;
>  	int ret = -EINVAL;
> +#ifdef CONFIG_ACPI_GTDT
> +	struct arch_timer_data data;
> +#endif
>  
>  	np = of_find_matching_node(NULL, arch_timer_of_match);
>  	if (!np) {
> @@ -397,6 +400,11 @@ static int kvm_timer_get_ppi(unsigned int *ppi)
>  	of_node_put(np);
>  
>  skip_of:
> +#ifdef CONFIG_ACPI_GTDT
> +	if (!*ppi && !gtdt_arch_timer_data_init(NULL, &data))
> +		*ppi = data.virt_ppi;
> +#endif
> +
>  	if (*ppi)
>  		return 0;
>  
> 

As I already pointed out in another thread hacking some KVM ACPI stuff,
this is the wrong approach.

We should have a *common* accessor in the timer code that exports the
relevant information, whatever the firmware "du jour" is.

See Julien's series, which seems to address the issue in a much more
convincing way:

https://lists.cs.columbia.edu/pipermail/kvmarm/2016-February/018531.html

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...