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From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Anthony PERARD <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jordan Justen <jordan.l.justen@intel.com>,
	devel@edk2.groups.io, Julien Grall <julien.grall@arm.com>,
	xen-devel@lists.xenproject.org, Laszlo Ersek <lersek@redhat.com>
Subject: Re: [Xen-devel] [edk2-devel] [PATCH v4 35/35] OvmfPkg/OvmfXen: use RealTimeClockRuntimeDxe from EmbeddedPkg
Date: Thu, 8 Aug 2019 17:19:20 +0200	[thread overview]
Message-ID: <20190808151920.uqwzdbe72w7fotf5@Air-de-Roger> (raw)
In-Reply-To: <20190808140348.GW1242@perard.uk.xensource.com>

On Thu, Aug 08, 2019 at 03:03:48PM +0100, Anthony PERARD wrote:
> On Wed, Aug 07, 2019 at 06:09:57PM +0200, Roger Pau Monné wrote:
> > On Mon, Jul 29, 2019 at 04:39:44PM +0100, Anthony PERARD wrote:
> > > A Xen PVH guest doesn't have a RTC that OVMF would expect, so
> > > PcatRealTimeClockRuntimeDxe fails to initialize and prevent the
> > > firmware from finish to boot. To prevent that, we will use
> > > XenRealTimeClockLib which simply always return the same time.
> > > This will work on both Xen PVH and HVM guests.
> > 
> > Not that this is not correct, but what's the point in requiring a
> > clock if it can be faked by always returning the same value?
> 
> It's not a clock that is required, it is a library that implements
> RealTimeClockLib. Something needs it, so it is provided, even if it is
> only to display the "current time".
> 
> > It seems like it's usage is not really required, and could indeed be
> > dropped altogether?
> 
> Way to much work to drop it. Also, I don't work to fork OVMF.
> 
> The ARM implementation of OVMF for Xen does the same thing and simply
> always return the same value.
> 
> > Alternatively, there's the PV clock which is available to PVH guests
> > and will return a proper time.
> 
> We might need to do that one day I guess, but right now it is just a
> nice to have.

Ack, thanks for the explanation.

Roger.

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  reply	other threads:[~2019-08-08 15:19 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-29 15:39 [Xen-devel] [PATCH v4 00/35] Specific platform to run OVMF in Xen PVH and HVM guests Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 01/35] OvmfPkg/ResetSystemLib: Add missing dependency on PciLib Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 02/35] OvmfPkg: Create platform OvmfXen Anthony PERARD
2019-07-30  9:13   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 03/35] OvmfPkg: Introduce XenResetVector Anthony PERARD
2019-07-30  9:16   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 04/35] OvmfPkg: Introduce XenPlatformPei Anthony PERARD
2019-07-30  9:21   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 05/35] OvmfPkg/OvmfXen: Creating an ELF header Anthony PERARD
2019-07-30  9:25   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 06/35] OvmfPkg/XenResetVector: Add new entry point for Xen PVH Anthony PERARD
2019-07-30  9:33   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-07 11:37   ` [Xen-devel] " Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 07/35] OvmfPkg/XenResetVector: Saving start of day pointer for PVH guests Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 08/35] OvmfPkg/XenResetVector: Allow jumpstart from either hvmloader or PVH Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU Anthony PERARD
2019-07-30  9:41   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-07 14:25   ` [Xen-devel] " Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 10/35] OvmfPkg/XenPlatformPei: Detect OVMF_INFO from hvmloader Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 11/35] OvmfPkg/XenPlatformPei: Use mXenHvmloaderInfo to get E820 Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 12/35] OvmfPkg/XenPlatformPei: Grab RSDP from PVH guest start of day struct Anthony PERARD
2019-08-07 14:35   ` [Xen-devel] [edk2-devel] " Roger Pau Monné
2019-08-08 10:26     ` Anthony PERARD
2019-08-08 10:40       ` Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 13/35] OvmfPkg/Library/XenPlatformLib: New library Anthony PERARD
2019-07-30  9:57   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 14/35] OvmfPkg/AcpiPlatformDxe: Use XenPlatformLib Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 15/35] OvmfPkg/AcpiPlatformDxe: Use Xen PVH RSDP if it exist Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 16/35] OvmfPkg/XenHypercallLib: Enable it in PEIM Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 17/35] OvmfPkg/XenPlatformPei: Reinit XenHypercallLib Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 18/35] OvmfPkg/XenPlatformPei: Introduce XenHvmloaderDetected Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 19/35] OvmfPkg/XenPlatformPei: Setup HyperPages earlier Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 20/35] OvmfPkg/XenPlatformPei: Introduce XenPvhDetected Anthony PERARD
2019-08-07 15:03   ` [Xen-devel] [edk2-devel] " Roger Pau Monné
2019-08-08 10:38     ` Anthony PERARD
2019-08-08 10:43       ` Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 21/35] OvmfPkg: Import XENMEM_memory_map hypercall to Xen/memory.h Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 22/35] OvmfPkg/XenPlatformPei: no hvmloader: get the E820 table via hypercall Anthony PERARD
2019-08-07 15:14   ` [Xen-devel] [edk2-devel] " Roger Pau Monné
2019-08-08 10:41     ` Anthony PERARD
2019-08-08 10:45       ` Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 23/35] OvmfPkg/XenPlatformPei: Rework memory detection Anthony PERARD
2019-07-30 11:45   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-30 12:18     ` Laszlo Ersek
2019-08-07 15:34   ` [Xen-devel] " Roger Pau Monné
2019-08-08 11:13     ` Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 24/35] OvmfPkg/XenPlatformPei: Reserve VGA memory region, to boot Linux Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 25/35] OvmfPkg/XenPlatformPei: Ignore missing PCI Host Bridge on Xen PVH Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 26/35] OvmfPkg/XenPlatformLib: Cache result for XenDetected Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 27/35] OvmfPkg/PlatformBootManagerLib: Use XenDetected from XenPlatformLib Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 28/35] OvmfPkg/PlatformBootManagerLib: Handle the absence of PCI bus on Xen PVH Anthony PERARD
2019-08-07 15:50   ` [Xen-devel] [edk2-devel] " Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 29/35] OvmfPkg/OvmfXen: Override PcdFSBClock to Xen vLAPIC timer frequency Anthony PERARD
2019-08-07 15:54   ` [Xen-devel] [edk2-devel] " Roger Pau Monné
2019-08-08 13:28     ` Anthony PERARD
2019-08-08 13:44       ` Roger Pau Monné
2019-08-08 14:26         ` Anthony PERARD
2019-08-08 15:18           ` Roger Pau Monné
2019-08-12 14:45             ` Anthony PERARD
2019-08-08 20:27         ` Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 30/35] OvmfPkg/OvmfXen: Introduce XenTimerDxe Anthony PERARD
2019-07-30 12:30   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 31/35] OvmfPkg/PlatformBootManagerLib: Use a Xen console for ConOut/ConIn Anthony PERARD
2019-07-30 12:34   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-07 16:00   ` Roger Pau Monné
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 32/35] OvmfPkg: Introduce PcdXenGrantFrames Anthony PERARD
2019-07-30 12:47   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 33/35] OvmfPkg: Introduce XenIoPvhDxe to initialize Grant Tables Anthony PERARD
2019-07-30 13:01   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-08-07 16:07   ` Roger Pau Monné
2019-08-08 13:53     ` Anthony PERARD
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 34/35] OvmfPkg: Move XenRealTimeClockLib from ArmVirtPkg Anthony PERARD
2019-07-30 13:05   ` [Xen-devel] [edk2-devel] " Laszlo Ersek
2019-07-29 15:39 ` [Xen-devel] [PATCH v4 35/35] OvmfPkg/OvmfXen: use RealTimeClockRuntimeDxe from EmbeddedPkg Anthony PERARD
2019-08-07 16:09   ` [Xen-devel] [edk2-devel] " Roger Pau Monné
2019-08-08 14:03     ` Anthony PERARD
2019-08-08 15:19       ` Roger Pau Monné [this message]
2019-07-30 12:38 ` [Xen-devel] [edk2-devel] [PATCH v4 00/35] Specific platform to run OVMF in Xen PVH and HVM guests Laszlo Ersek
2019-07-30 13:10 ` Laszlo Ersek
2019-08-12 15:12   ` Anthony PERARD
2019-08-13  9:02     ` Laszlo Ersek

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