linux-kernel - Re: [PATCH RESEND] kvm: make kvm_vcpu_(un)map dependency on CONFIG_HAS

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Message-ID: <20190521055117.GC25473@unicorn.suse.cz>
Date:   Tue, 21 May 2019 07:51:17 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        KarimAllah Ahmed <karahmed@...zon.de>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] kvm: make kvm_vcpu_(un)map dependency on
 CONFIG_HAS_IOMEM explicit

On Mon, May 20, 2019 at 03:45:29PM -0700, Bjorn Andersson wrote:
> On Mon, May 20, 2019 at 9:44 AM Michal Kubecek <mkubecek@...e.cz> wrote:
> >
> > Recently introduced functions kvm_vcpu_map() and kvm_vcpu_unmap() call
> > memremap() and memunmap() which are only available if HAS_IOMEM is enabled
> > but this dependency is not explicit, so that the build fails with HAS_IOMEM
> > disabled.
> >
> > As both function are only used on x86 where HAS_IOMEM is always enabled,
> > the easiest fix seems to be to only provide them when HAS_IOMEM is enabled.
> >
> > Fixes: e45adf665a53 ("KVM: Introduce a new guest mapping API")
> > Signed-off-by: Michal Kubecek <mkubecek@...e.cz>
> 
> Hi Michal,
> 
> I see the same build issue on arm64 and as CONFIG_HAS_IOMEM is set
> there this patch has no effect on solving that. Instead I had to
> include linux/io.h in kvm_main.c to make it compile.

This sounds like a different problem which was already resolved in
mainline by commit c011d23ba046 ("kvm: fix compilation on aarch64")
which is present in v5.2-rc1. The issue I'm trying to address is link
time failure (unresolved reference to memremap()/memunmap()) when
CONFIG_HAS_IOMEM is disabled (in our case it affects a special
minimalistic s390x config for zfcpdump).

Michal