Re: [PATCH 0/8] arm64 kexec kernel patches V6

[Dave Young <dyoung@redhat.com>]

On 11/27/14 at 02:19pm, Dave Young wrote:
> Geoff,
> 
> Is there any Linaro card for the KVM soft restart issue?
> 
> Ccing Andrew Jones since he might be interested in KVM issues.
> 
> On 11/14/14 at 01:22am, Geoff Levand wrote:
> > Hi All,
> > 
> > This series adds the core support for kexec re-boots on arm64.  I have tested
> > with the ARM VE fast model, the ARM Base model and the ARM Foundation
> > model with various kernel config options for both the first and second stage
> > kernels.
> > 
> > To load a second stage kernel and execute a kexec re-boot on arm64 my patches to
> > kexec-tools [2], which have not yet been merged upstream, are needed.
> > 
> > Patches 1-3 rework the arm64 hcall mechanism to give the arm64 soft_restart()
> > routine the ability to switch exception levels from EL1 to EL2 for kernels that
> > were entered in EL2.
> > 
> > Patch 4 moves proc-macros.S from arm64/mm to arm64/include/asm so that the
> > dcache_line_size macro it defines can be uesd by kexec's relocate kernel
> > routine.
> > 
> > Patches 5-8 add the actual kexec support.
> > 
> > Please consider all patches for inclusion.  Any comments or suggestions on how 
> > to improve are welcome.
> > 
> > [1]  https://git.linaro.org/people/geoff.levand/linux-kexec.git
> > [2]  https://git.linaro.org/people/geoff.levand/kexec-tools.git
> > 
> > Several things are known to have problems on kexec re-boot:
> > 
> > spin-table
> > ----------
> > 
> > PROBLEM: The spin-table enable method does not implement all the methods needed
> > for CPU hot-plug, so the first stage kernel cannot be shutdown properly.
> > 
> > WORK-AROUND: Upgrade to system firmware that provides PSCI enable method
> > support, OR build the first stage kernel with CONFIG_SMP=n, OR pass 'maxcpus=1'
> > on the first stage kernel command line.
> > 
> > FIX: Upgrade system firmware to provide PSCI enable method support or add
> > missing spin-table support to the kernel.
> > 
> > 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.
> > 
> > WORK-AROUND:  Build the first stage kernel with CONFIG_KVM=n.
> > 
> > FIX: Fix KVM to support soft_restart().  KVM needs to restore default exception
> > vectors, etc.
> > 
> > UEFI
> > ----
> > 
> > PROBLEM: UEFI does not manage its runtime services virtual mappings in a way
> > that is compatible with a kexec re-boot, so the second stage kernel hangs on
> > boot-up.
> > 
> > WORK-AROUND: Disable UEFI in firmware, OR use EFI uboot emulation if provided
> > by your firmware.
> > 
> > FIX: Fix kernel to manage UEFI virtual mappings properly.
> > 
> > /memreserve/
> > ----------
> > 
> > PROBLEM: The use of device tree /memreserve/ entries is not compatible with
> > kexec re-boot.  The second stage kernel will use the reserved regions and the
> > system will become unstable.
> > 
> > WORK-AROUND: Pass a user specified DTB using the kexec --dtb option.
> > 
> > FIX: Convert device tree source files (.dts) and/or bootloaders to use device
> > tree reserved-memory nodes to specify reserved memory or provide an in kernel
> > mechanism to export the /memreserve/ entries to user space.
> > 
> > ACPI
> > ----
> > 
> > PROBLEM: The kernel for ACPI based systems does not export a device tree to the
> > standard user space location of 'proc/device-tree'.  Current applications
> > expect to access device tree information from this standard location.
> > 
> > WORK-AROUND: Disable ACPI in firmware, OR pass 'acpi=off' on the first stage
> > kernel command line, OR pass a user specified DTB using the kexec --dtb option.
> > 
> > FIX: Fix ACPI kernel support to export device tree information suitable for a
> > kexec re-boot, and if this information is exported to somewhere other than
> > 'proc/device-tree' update existing kexec user applications to use this new
> > interface.
> > 
> > ----------------------------------------------------------------
> > The following changes since commit 302cd37c417d59549d073a8986fd028998409cb9:
> > 
> >   arm64: kvm: eliminate literal pool entries (2014-11-07 15:04:54 +0000)
> > 
> > are available in the git repository at:
> > 
> >   git://git.linaro.org/people/geoff.levand/linux-kexec.git kexec-v6
> > 

Tested your master branch, works for me with below setup:
UEFI boot, CONFIG_KVM=n, maxcpus=1, --lite

But --dtb still does not work if there's no /proc/device-tree, failed as below:
unrecoverable error: could not scan "/proc/device-tree/": No such file or directory.

kexec without --lite also does not work, looks like it hangs after "Bye" ..

Thanks
Dave

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