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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wei Liu <wei.liu@kernel.org>,
	Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
Cc: virtualization@lists.linux-foundation.org,
	Linux Kernel List <linux-kernel@vger.kernel.org>,
	Michael Kelley <mikelley@microsoft.com>,
	Vineeth Pillai <viremana@linux.microsoft.com>,
	Sunil Muthuswamy <sunilmut@microsoft.com>,
	Nuno Das Neves <nudasnev@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH RFC v1 05/18] clocksource/hyperv: use MSR-based access if running as root
Date: Tue, 15 Sep 2020 12:10:04 +0200	[thread overview]
Message-ID: <874knzl5ab.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200914112802.80611-6-wei.liu@kernel.org>

Wei Liu <wei.liu@kernel.org> writes:

> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
>  drivers/clocksource/hyperv_timer.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 09aa44cb8a91..fe96082ce85e 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -426,6 +426,9 @@ static bool __init hv_init_tsc_clocksource(void)
>  	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
>  		return false;
>  
> +	if (hv_root_partition)
> +		return false;
> +

Out of pure curiosity,

TSC page clocksource seems to be available to the root partition (as
HV_MSR_REFERENCE_TSC_AVAILABLE is set), why don't we use it? (I
understand that with TSC scaling support in modern CPUs even migration
is a no-issue and we can use raw TSC but this all seems to be
independent from root/non-root partition question).

>  	hv_read_reference_counter = read_hv_clock_tsc;
>  	phys_addr = virt_to_phys(hv_get_tsc_page());

-- 
Vitaly


WARNING: multiple messages have this Message-ID (diff)
From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wei Liu <wei.liu@kernel.org>,
	Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
Cc: Wei Liu <wei.liu@kernel.org>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	virtualization@lists.linux-foundation.org,
	Linux Kernel List <linux-kernel@vger.kernel.org>,
	Nuno Das Neves <nudasnev@microsoft.com>,
	Sunil Muthuswamy <sunilmut@microsoft.com>,
	Michael Kelley <mikelley@microsoft.com>,
	Vineeth Pillai <viremana@linux.microsoft.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH RFC v1 05/18] clocksource/hyperv: use MSR-based access if running as root
Date: Tue, 15 Sep 2020 12:10:04 +0200	[thread overview]
Message-ID: <874knzl5ab.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200914112802.80611-6-wei.liu@kernel.org>

Wei Liu <wei.liu@kernel.org> writes:

> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
>  drivers/clocksource/hyperv_timer.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 09aa44cb8a91..fe96082ce85e 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -426,6 +426,9 @@ static bool __init hv_init_tsc_clocksource(void)
>  	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
>  		return false;
>  
> +	if (hv_root_partition)
> +		return false;
> +

Out of pure curiosity,

TSC page clocksource seems to be available to the root partition (as
HV_MSR_REFERENCE_TSC_AVAILABLE is set), why don't we use it? (I
understand that with TSC scaling support in modern CPUs even migration
is a no-issue and we can use raw TSC but this all seems to be
independent from root/non-root partition question).

>  	hv_read_reference_counter = read_hv_clock_tsc;
>  	phys_addr = virt_to_phys(hv_get_tsc_page());

-- 
Vitaly

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

  reply	other threads:[~2020-09-15 10:10 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 11:27 [PATCH RFC v1 00/18] Introducing Linux root partition support for Microsoft Hypervisor Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 01/18] asm-generic/hyperv: change HV_CPU_POWER_MANAGEMENT to HV_CPU_MANAGEMENT Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 02/18] x86/hyperv: detect if Linux is the root partition Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 03/18] Drivers: hv: vmbus: skip VMBus initialization if Linux is root Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 04/18] iommu/hyperv: don't setup IRQ remapping when running as root Wei Liu
2020-09-14 11:27   ` Wei Liu
2020-09-18  9:12   ` Joerg Roedel
2020-09-18  9:12     ` Joerg Roedel
2020-09-18  9:12     ` Joerg Roedel
2020-09-14 11:27 ` [PATCH RFC v1 05/18] clocksource/hyperv: use MSR-based access if " Wei Liu
2020-09-15 10:10   ` Vitaly Kuznetsov [this message]
2020-09-15 10:10     ` Vitaly Kuznetsov
2020-09-15 10:32     ` Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 06/18] x86/hyperv: allocate output arg pages if required Wei Liu
2020-09-15 10:16   ` Vitaly Kuznetsov
2020-09-15 10:16     ` Vitaly Kuznetsov
2020-09-15 12:43     ` Wei Liu
2020-09-16 15:42       ` Wei Liu
2020-09-16 16:10         ` Vitaly Kuznetsov
2020-09-16 16:10           ` Vitaly Kuznetsov
2020-09-14 11:27 ` [PATCH RFC v1 07/18] x86/hyperv: extract partition ID from Microsoft Hypervisor if necessary Wei Liu
2020-09-15 10:27   ` Vitaly Kuznetsov
2020-09-15 10:27     ` Vitaly Kuznetsov
2020-09-16 16:32     ` Wei Liu
2020-10-27 12:19       ` Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 08/18] x86/hyperv: handling hypercall page setup for root Wei Liu
2020-09-15 10:32   ` Vitaly Kuznetsov
2020-09-15 10:32     ` Vitaly Kuznetsov
2020-09-15 10:37     ` Wei Liu
2020-09-15 11:02       ` Vitaly Kuznetsov
2020-09-15 11:02         ` Vitaly Kuznetsov
2020-09-15 11:16         ` Wei Liu
2020-09-15 11:23           ` Vitaly Kuznetsov
2020-09-15 11:23             ` Vitaly Kuznetsov
2020-09-15 11:27             ` Wei Liu
2020-09-16 21:34       ` [EXTERNAL] " Sunil Muthuswamy
2020-09-16 21:34         ` Sunil Muthuswamy via Virtualization
2020-09-17 11:06         ` Vitaly Kuznetsov
2020-09-17 11:06           ` Vitaly Kuznetsov
2020-09-14 11:59 ` [PATCH RFC v1 09/18] x86/hyperv: provide a bunch of helper functions Wei Liu
2020-09-15 11:00   ` Vitaly Kuznetsov
2020-09-15 11:00     ` Vitaly Kuznetsov
2020-10-27 13:10     ` Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 10/18] x86/hyperv: implement and use hv_smp_prepare_cpus Wei Liu
2020-09-15 11:14   ` Vitaly Kuznetsov
2020-09-15 11:14     ` Vitaly Kuznetsov
2020-10-27 13:47     ` Wei Liu
2020-10-27 13:56       ` Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 11/18] asm-generic/hyperv: update hv_msi_entry Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 12/18] asm-generic/hyperv: update hv_interrupt_entry Wei Liu
2020-10-01 14:33   ` Rob Herring
2020-10-01 14:33     ` Rob Herring
2020-09-14 11:59 ` [PATCH RFC v1 13/18] asm-generic/hyperv: introduce hv_device_id and auxiliary structures Wei Liu
2020-09-15 11:16   ` Vitaly Kuznetsov
2020-09-15 11:16     ` Vitaly Kuznetsov
2020-09-15 11:59     ` Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 14/18] asm-generic/hyperv: import data structures for mapping device interrupts Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 15/18] x86/apic/msi: export pci_msi_get_hwirq Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 16/18] x86/hyperv: implement MSI domain for root partition Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 17/18] x86/ioapic: export a few functions and data structures via io_apic.h Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 18/18] x86/hyperv: handle IO-APIC when running as root Wei Liu

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