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From: Richard Cochran <richardcochran@gmail.com>
To: Jianyong Wu <jianyong.wu@arm.com>
Cc: maz@kernel.org, justin.he@arm.com, Wei.Chen@arm.com,
	kvm@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com,
	steven.price@arm.com, john.stultz@linaro.org, yangbo.lu@nxp.com,
	pbonzini@redhat.com, tglx@linutronix.de, nd@arm.com,
	will@kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v12 10/11] arm64: add mechanism to let user choose which counter to return
Date: Sat, 23 May 2020 18:47:21 -0700
Message-ID: <20200524014721.GB335@localhost> (raw)
In-Reply-To: <20200522083724.38182-11-jianyong.wu@arm.com>

On Fri, May 22, 2020 at 04:37:23PM +0800, Jianyong Wu wrote:

> To use this feature, you should call PTP_EXTTS_REQUEST(2) ioctl with flag
> set bit PTP_KVM_ARM_PHY_COUNTER in its argument then call
> PTP_SYS_OFFSET_PRECISE(2) ioctl to get the cross timestamp and phyical
> counter will return. If the bit not set or no call for PTP_EXTTS_REQUEST2,
> virtual counter will return by default.

I'm sorry, but NAK on this completely bizarre twisting of the user
space API.

> diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
> index fef72f29f3c8..8b0a7b328bcd 100644
> --- a/drivers/ptp/ptp_chardev.c
> +++ b/drivers/ptp/ptp_chardev.c
> @@ -123,6 +123,9 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
>  	struct timespec64 ts;
>  	int enable, err = 0;
>  
> +#ifdef CONFIG_ARM64
> +	static long flag;
> +#endif
>  	switch (cmd) {
>  
>  	case PTP_CLOCK_GETCAPS:
> @@ -149,6 +152,24 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
>  			err = -EFAULT;
>  			break;
>  		}
> +
> +#ifdef CONFIG_ARM64
> +		/*
> +		 * Just using this ioctl to tell kvm ptp driver to get PHC
> +		 * with physical counter, so if bit PTP_KVM_ARM_PHY_COUNTER
> +		 * is set then just exit directly.
> +		 * In most cases, we just need virtual counter from host and
> +		 * there is limited scenario using this to get physical counter
> +		 * in guest.
> +		 * Be careful to use this as there is no way to set it back
> +		 * unless you reinstall the module.
> +		 * This is only for arm64.
> +		 */
> +		if (req.extts.flags & PTP_KVM_ARM_PHY_COUNTER) {
> +			flag = 1;
> +			break;
> +		}
> +#endif

This file contains the generic PTP Hardware Clock character device
implementation.  It is no place for platform specific hacks.

Sorry,
Richard
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  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22  8:37 [RFC PATCH v12 0/11] Enable ptp_kvm for arm64 Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 01/11] arm64: Probe for the presence of KVM hypervisor services during boot Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 02/11] arm/arm64: KVM: Advertise KVM UID to guests via SMCCC Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 03/11] psci: export smccc conduit get helper Jianyong Wu
2020-05-22 13:12   ` Sudeep Holla
2020-05-25  1:37     ` Jianyong Wu
2020-05-26 10:10       ` Sudeep Holla
2020-05-22  8:37 ` [RFC PATCH v12 04/11] ptp: Reorganize ptp_kvm modules to make it arch-independent Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 05/11] time: Add mechanism to recognize clocksource in time_get_snapshot Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 06/11] clocksource: Add clocksource id for arm arch counter Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 07/11] psci: Add hypercall service for kvm ptp Jianyong Wu
2020-05-22 14:18   ` Steven Price
2020-05-25  2:11     ` Jianyong Wu
2020-05-26 11:02       ` Steven Price
2020-05-22  8:37 ` [RFC PATCH v12 08/11] ptp: arm64: Enable ptp_kvm for arm/arm64 Jianyong Wu
2020-05-22  8:37 ` [RFC PATCH v12 09/11] ptp: extend input argument for getcrosstimestamp API Jianyong Wu
2020-05-24  1:42   ` Richard Cochran
2020-05-22  8:37 ` [RFC PATCH v12 10/11] arm64: add mechanism to let user choose which counter to return Jianyong Wu
2020-05-24  1:47   ` Richard Cochran [this message]
2020-05-24  2:11   ` Richard Cochran
2020-05-25  4:50     ` Jianyong Wu
2020-05-25  6:16       ` Richard Cochran
2020-05-25  6:29         ` Jianyong Wu
2020-05-25  9:17     ` Marc Zyngier
2020-05-25 14:18       ` Jianyong Wu
2020-05-25 15:28         ` Marc Zyngier
2020-05-22  8:37 ` [RFC PATCH v12 11/11] arm64: Add kvm capability check extension for ptp_kvm Jianyong Wu

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