linux-kernel - Re: [PATCH 4.19 65/84] arm64: KVM: Trap VM ops when ARM64_WORKAROUND_CAVIUM_TX2_219

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Date:   Sat, 11 Jan 2020 18:44:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     open list <linux-kernel@...r.kernel.org>,
        linux- stable <stable@...r.kernel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        lkft-triage@...ts.linaro.org
Subject: Re: [PATCH 4.19 65/84] arm64: KVM: Trap VM ops when
 ARM64_WORKAROUND_CAVIUM_TX2_219_TVM is set

On Sat, Jan 11, 2020 at 06:00:19PM +0530, Naresh Kamboju wrote:
> On Sat, 11 Jan 2020 at 15:49, Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > From: Marc Zyngier <marc.zyngier@....com>
> >
> > commit d3ec3a08fa700c8b46abb137dce4e2514a6f9668 upstream.
> >
> > In order to workaround the TX2-219 erratum, it is necessary to trap
> > TTBRx_EL1 accesses to EL2. This is done by setting HCR_EL2.TVM on
> > guest entry, which has the side effect of trapping all the other
> > VM-related sysregs as well.
> >
> > To minimize the overhead, a fast path is used so that we don't
> > have to go all the way back to the main sysreg handling code,
> > unless the rest of the hypervisor expects to see these accesses.
> >
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> > Signed-off-by: Will Deacon <will@...nel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> On stable-rc 4.19 all arm64 builds failed due to this error,
> 
> arch/arm64/kvm/hyp/switch.c: In function 'handle_tx2_tvm':
> arch/arm64/kvm/hyp/switch.c:438:2: error: implicit declaration of
> function '__kvm_skip_instr'; did you mean 'kvm_skip_instr'?
> [-Werror=implicit-function-declaration]
>   __kvm_skip_instr(vcpu);
>   ^~~~~~~~~~~~~~~~
>   kvm_skip_instr
> cc1: some warnings being treated as errors
> scripts/Makefile.build:303: recipe for target
> 'arch/arm64/kvm/hyp/switch.o' failed
> 
> Full build log,
> https://ci.linaro.org/view/lkft/job/openembedded-lkft-linux-stable-rc-4.19/DISTRO=lkft,MACHINE=hikey,label=docker-lkft/413/consoleText
> 

Crap, this one patch has caused more problems...

I'll go drop it, thanks for verifying that I shouldn't have backported
it in the first place :)

greg k-h