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From: Mark Rutland <mark.rutland@arm.com>
To: Geoff Levand <geoff@infradead.org>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Marc Zyngier <Marc.Zyngier@arm.com>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	Will Deacon <Will.Deacon@arm.com>,
	"hanjun.guo@linaro.org" <hanjun.guo@linaro.org>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"christoffer.dall@linaro.org" <christoffer.dall@linaro.org>
Subject: Re: [PATCH 0/6] arm64 kexec kernel patches V8
Date: Fri, 20 Mar 2015 19:48:38 +0000	[thread overview]
Message-ID: <20150320194838.GD24455@leverpostej> (raw)
In-Reply-To: <cover.1426793116.git.geoff@infradead.org>

On Thu, Mar 19, 2015 at 08:35:27PM +0000, Geoff Levand wrote:
> Hi All,

Hi Geoff,

As a heads-up, I'm not going to have the chanec to review this until
after the FW summit next week.

[...]

> KVM
> ---
> 
> PROBLEM: KVM acquires hypervisor resources on startup, but does not free those
> resources on shutdown, so the first stage kernel cannot be shutdown properly
> when using kexec.
> 
> WORK-AROUND: Build the first stage kernel with CONFIG_KVM=n, or apply KVM bug
> fix patches from [1].
> 
> FIX: Takahiro Akashi has preliminary patches to fix the KVM shutdown problem.  I
> have those in my master branch at [1].  KVM + kexec works properly with that
> branch.  Patches neeeded:
> 
>  arm64: kvm: add a cpu tear-down function
>  arm64: kexec: fix kvm issue
>  arm64/kvm: Remove !KEXEC Kconfig dependency
>  arm64/kexec: Enable kexec in the arm64 defconfig

These (or some descendents thereof) are going to be a prerequisite for
kexec.

> /memreserve/
> ----------
> 
> PROBLEM: Device tree /memreserve/ entries are not available in
> /proc/device-tree.  For systems that have /memreserve/ entries and use
> /proc/device-tree during kexec, the second stage kernel will use the reserved
> regions and the system will become unstable.
> 
> WORK-AROUND: Enable the kernel config option CONFIG_SYSFS=y to expose a binary
> device tree to user space at /sys/firmware/fdt that includes /memreserve/
> entries OR pass a user specified DTB using the kexec --dtb option.
> 
> FIX: This is expected behavior.  To maximize user support, rework device tree
> definitions to not use /memreserve/ entries.

I'd say that requiring CONFIG_SYSFS is the real fix here. That's a
kernel change that maximises compatibility with DTBs (which we don't
really have control over).

I hope that the tools warn somehow if they cannot see the fdt.

Mark.

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: mark.rutland@arm.com (Mark Rutland)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/6] arm64 kexec kernel patches V8
Date: Fri, 20 Mar 2015 19:48:38 +0000	[thread overview]
Message-ID: <20150320194838.GD24455@leverpostej> (raw)
In-Reply-To: <cover.1426793116.git.geoff@infradead.org>

On Thu, Mar 19, 2015 at 08:35:27PM +0000, Geoff Levand wrote:
> Hi All,

Hi Geoff,

As a heads-up, I'm not going to have the chanec to review this until
after the FW summit next week.

[...]

> KVM
> ---
> 
> PROBLEM: KVM acquires hypervisor resources on startup, but does not free those
> resources on shutdown, so the first stage kernel cannot be shutdown properly
> when using kexec.
> 
> WORK-AROUND: Build the first stage kernel with CONFIG_KVM=n, or apply KVM bug
> fix patches from [1].
> 
> FIX: Takahiro Akashi has preliminary patches to fix the KVM shutdown problem.  I
> have those in my master branch at [1].  KVM + kexec works properly with that
> branch.  Patches neeeded:
> 
>  arm64: kvm: add a cpu tear-down function
>  arm64: kexec: fix kvm issue
>  arm64/kvm: Remove !KEXEC Kconfig dependency
>  arm64/kexec: Enable kexec in the arm64 defconfig

These (or some descendents thereof) are going to be a prerequisite for
kexec.

> /memreserve/
> ----------
> 
> PROBLEM: Device tree /memreserve/ entries are not available in
> /proc/device-tree.  For systems that have /memreserve/ entries and use
> /proc/device-tree during kexec, the second stage kernel will use the reserved
> regions and the system will become unstable.
> 
> WORK-AROUND: Enable the kernel config option CONFIG_SYSFS=y to expose a binary
> device tree to user space at /sys/firmware/fdt that includes /memreserve/
> entries OR pass a user specified DTB using the kexec --dtb option.
> 
> FIX: This is expected behavior.  To maximize user support, rework device tree
> definitions to not use /memreserve/ entries.

I'd say that requiring CONFIG_SYSFS is the real fix here. That's a
kernel change that maximises compatibility with DTBs (which we don't
really have control over).

I hope that the tools warn somehow if they cannot see the fdt.

Mark.

  parent reply	other threads:[~2015-03-20 19:48 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-19 20:35 [PATCH 0/6] arm64 kexec kernel patches V8 Geoff Levand
2015-03-19 20:35 ` Geoff Levand
2015-03-19 20:35 ` [PATCH 2/6] arm64: Convert hcalls to use HVC immediate value Geoff Levand
2015-03-19 20:35   ` Geoff Levand
2015-09-23 19:21   ` Timur Tabi
2015-09-23 19:21     ` Timur Tabi
2015-09-24 19:04     ` Geoff Levand
2015-09-24 19:04       ` Geoff Levand
2015-03-19 20:35 ` [PATCH 4/6] arm64: Add EL2 switch to soft_restart Geoff Levand
2015-03-19 20:35   ` Geoff Levand
2015-03-19 20:35 ` [PATCH 3/6] arm64: Add new hcall HVC_CALL_FUNC Geoff Levand
2015-03-19 20:35   ` Geoff Levand
2015-03-19 20:35 ` [PATCH 1/6] arm64: Fold proc-macros.S into assembler.h Geoff Levand
2015-03-19 20:35   ` Geoff Levand
2015-03-19 20:35 ` [PATCH 5/6] arm64/kexec: Add core kexec support Geoff Levand
2015-03-19 20:35   ` Geoff Levand
2015-04-07 16:38   ` Suzuki K. Poulose
2015-04-07 16:38     ` Suzuki K. Poulose
2015-04-07 22:48     ` Geoff Levand
2015-04-07 22:48       ` Geoff Levand
2015-04-07 23:01   ` [PATCH V2 " Geoff Levand
2015-04-07 23:01     ` Geoff Levand
2015-03-19 20:35 ` [PATCH 6/6] arm64/kexec: Add pr_devel output Geoff Levand
2015-03-19 20:35   ` Geoff Levand
2015-03-20 19:48 ` Mark Rutland [this message]
2015-03-20 19:48   ` [PATCH 0/6] arm64 kexec kernel patches V8 Mark Rutland
2015-04-03 16:48 ` Geoff Levand
2015-04-03 16:48   ` Geoff Levand
2015-04-08 11:16 ` Suzuki K. Poulose
2015-04-08 11:16   ` Suzuki K. Poulose
2015-04-08 17:14   ` Geoff Levand
2015-04-08 17:14     ` Geoff Levand
2015-07-03  3:39     ` Pratyush Anand
2015-07-03  3:39       ` Pratyush Anand
2015-07-06 17:23       ` Geoff Levand
2015-07-06 17:23         ` Geoff Levand

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