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From: Michael Kelley <mikelley@microsoft.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	gregkh <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	"olaf@aepfle.de" <olaf@aepfle.de>,
	Andy Whitcroft <apw@canonical.com>,
	vkuznets <vkuznets@redhat.com>, Jason Wang <jasowang@redhat.com>,
	"marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>,
	KY Srinivasan <kys@microsoft.com>,
	Sunil Muthuswamy <sunilmut@microsoft.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	John Stultz <john.stultz@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Stephen Boyd <sboyd@kernel.org>
Subject: RE: [PATCH v6 07/10] arm64: hyperv: Initialize hypervisor on boot
Date: Wed, 18 Mar 2020 00:17:52 +0000
Message-ID: <MW2PR2101MB1052281E5B197F2AA8E4D622D7F70@MW2PR2101MB1052.namprd21.prod.outlook.com> (raw)
In-Reply-To: <CAK8P3a0+uBsurfQ4smjPDGkJQSkMe-TxJ4cWR_EZXgDR4-bAWQ@mail.gmail.com>

From: Arnd Bergmann <arnd@arndb.de> Sent: Monday, March 16, 2020 1:30 AM
> 
> On Sat, Mar 14, 2020 at 4:36 PM Michael Kelley <mikelley@microsoft.com> wrote:
> >
> > Add ARM64-specific code to initialize the Hyper-V
> > hypervisor when booting as a guest VM. Provide functions
> > and data structures indicating hypervisor status that
> > are needed by VMbus driver.
> >
> > This code is built only when CONFIG_HYPERV is enabled.
> >
> > Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> > ---
> >  arch/arm64/hyperv/hv_core.c | 156
> ++++++++++++++++++++++++++++++++++++++++++++
> 
> As you are effectively adding a new clocksource driver here, please move the
> code to drivers/clocksource and send the patch to the respective maintainers
> (added to Cc here), splitting it out from the rest of the patch.
> 
> You should also describe why your platform doesn't just use the normal
> architected timer interface.
> 
> > +TIMER_ACPI_DECLARE(hyperv, ACPI_SIG_GTDT, hyperv_init);
> 
> This looks like it registers a driver for the same device as the normal
> arch timer. Won't that clash?
> 
>      Arnd

There is a Hyper-V clocksource driver in drivers/clocksource/hyperv_timer.c.
It is architecture independent and works for both x86 and ARM64.

The requirement here is really for a place to hang the general Hyper-V
initialization code.   On the x86 side, there's infrastructure already in place
to do hypervisor initialization, but nothing corresponding on the ARM64 side.
The TIMER_ACPI_DECLARE hook is admittedly a temporary approach, and I'm
happy to hear if someone has a better way to handle this.

FWIW, Hyper-V doesn't currently virtualize the ARM arch counter/timer for
guest VMs.  The Hyper-V synthetic counter/timer in the Hyper-V clocksource
driver is used on both ARM64 and x86.  But this Hyper-V init code doesn't actually
touch the GTDT device, so it won't interfere with the ARM arch counter/timer
when a future Hyper-V version does virtualize it.

Michael

  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-14 15:35 [PATCH v6 00/10] Subject: Enable Linux guests on Hyper-V on ARM64 Michael Kelley
2020-03-14 15:35 ` [PATCH v6 01/10] arm64: hyperv: Add core Hyper-V include files Michael Kelley
2020-03-15 17:31   ` Marc Zyngier
2020-03-18  0:10     ` Michael Kelley
2020-03-16  8:47   ` Arnd Bergmann
2020-03-18  0:12     ` Michael Kelley
2020-03-18 10:10       ` Arnd Bergmann
2020-03-19 21:31         ` Michael Kelley
2020-03-20 16:38           ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 02/10] arm/arm64: smccc-1.1: Add vendor specific owner definition Michael Kelley
2020-03-14 15:35 ` [PATCH v6 03/10] arm64: hyperv: Add hypercall and register access functions Michael Kelley
2020-03-14 15:35 ` [PATCH v6 04/10] arm64: hyperv: Add memory alloc/free functions for Hyper-V size pages Michael Kelley
2020-03-16  8:22   ` Arnd Bergmann
2020-03-16  8:30     ` gregkh
2020-03-16  8:30     ` Marc Zyngier
2020-03-16  8:32       ` Arnd Bergmann
2020-03-18  0:15         ` Michael Kelley
2020-03-18  9:57           ` Arnd Bergmann
2020-03-19 21:43             ` Michael Kelley
2020-03-20 16:28               ` Arnd Bergmann
2020-03-20 17:22                 ` Michael Kelley
2020-03-14 15:35 ` [PATCH v6 05/10] arm64: hyperv: Add interrupt handlers for VMbus and stimer Michael Kelley
2020-03-16  8:25   ` Arnd Bergmann
2020-03-18  0:16     ` Michael Kelley
2020-03-18  9:52       ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 06/10] arm64: hyperv: Add kexec and panic handlers Michael Kelley
2020-03-15 18:15   ` Marc Zyngier
2020-03-18  0:17     ` Michael Kelley
2020-03-14 15:35 ` [PATCH v6 07/10] arm64: hyperv: Initialize hypervisor on boot Michael Kelley
2020-03-16  8:29   ` Arnd Bergmann
2020-03-18  0:17     ` Michael Kelley [this message]
2020-03-18  9:44       ` Arnd Bergmann
2020-03-14 15:35 ` [PATCH v6 08/10] Drivers: hv: vmbus: Add hooks for per-CPU IRQ Michael Kelley
2020-03-14 15:35 ` [PATCH v6 09/10] arm64: efi: Export screen_info Michael Kelley
2020-03-16  8:20   ` Arnd Bergmann
2020-03-18  0:18     ` Michael Kelley
2020-03-18  9:26       ` Arnd Bergmann
2020-03-19 21:46         ` Michael Kelley
2020-05-13 14:26           ` Nikhil Mahale
2020-05-18  4:25             ` Nikhil Mahale
2020-05-18 12:51               ` Ard Biesheuvel
2020-05-22 11:14                 ` Nikhil Mahale
2020-05-22 11:32                   ` Ard Biesheuvel
2020-03-14 15:35 ` [PATCH v6 10/10] Drivers: hv: Enable Hyper-V code to be built on ARM64 Michael Kelley
     [not found] ` <20200318031130.5476-1-hdanton@sina.com>
2020-03-19 21:04   ` [PATCH v6 03/10] arm64: hyperv: Add hypercall and register access functions Michael Kelley

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