linux-kernel - Re: [PATCH] do not clean dummy variable in kexec path

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Message-ID: <20190806024413.GB6956@dhcp-128-65.nay.redhat.com>
Date:   Tue, 6 Aug 2019 10:44:13 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Matthew Garrett <mjg59@...gle.com>
Cc:     linux-efi <linux-efi@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        kexec@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        bhsharma@...hat.com
Subject: Re: [PATCH] do not clean dummy variable in kexec path

On 08/05/19 at 10:09am, Matthew Garrett wrote:
> On Mon, Aug 5, 2019 at 1:36 AM Dave Young <dyoung@...hat.com> wrote:
> >
> > kexec reboot fails randomly in UEFI based kvm guest.  The firmware
> > just reset while calling efi_delete_dummy_variable();  Unfortunately
> > I don't know how to debug the firmware, it is also possible a potential
> > problem on real hardware as well although nobody reproduced it.
> >
> > The intention of efi_delete_dummy_variable is to trigger garbage collection
> > when entering virtual mode.  But SetVirtualAddressMap can only run once
> > for each physical reboot, thus kexec_enter_virtual_mode is not necessarily
> > a good place to clean dummy object.
> 
> I agree that this isn't necessarily the best place to do this in the
> kexec case, but given we control the firmware, figuring out what's
> actually breaking seems like a good plan.

I'm more than glad to get the root cause, if you can help on debugging I
would like to share the efi var file etc.

But it is indeed a problem cause weird reset on end user part, but even if we can
not find the root cause (in firmware..)  I think we still need avoid it
with such workaround.

Thanks
Dave