linux-kernel - Re: [RFCv2 14/16] KVM: Handle protected memory in __kvm_map_gfn()/__kvm_unmap

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Date:   Thu, 22 Oct 2020 05:26:47 +0200
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        Liran Alon <liran.alon@...cle.com>,
        Mike Rapoport <rppt@...nel.org>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFCv2 14/16] KVM: Handle protected memory in
 __kvm_map_gfn()/__kvm_unmap_gfn()

On Tue, 20 Oct 2020 09:18:57 +0300
"Kirill A. Shutemov" <kirill@...temov.name> wrote:

> We cannot access protected pages directly. Use ioremap() to
> create a temporary mapping of the page. The mapping is destroyed
> on __kvm_unmap_gfn().
> 
> The new interface gfn_to_pfn_memslot_protected() is used to detect if
> the page is protected.
> 
> ioremap_cache_force() is a hack to bypass IORES_MAP_SYSTEM_RAM check in
> the x86 ioremap code. We need a better solution.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 +-
>  arch/powerpc/kvm/book3s_64_mmu_radix.c |  2 +-
>  arch/x86/include/asm/io.h              |  2 +
>  arch/x86/include/asm/pgtable_types.h   |  1 +
>  arch/x86/kvm/mmu/mmu.c                 |  6 ++-
>  arch/x86/mm/ioremap.c                  | 16 ++++++--
>  include/linux/kvm_host.h               |  3 +-
>  include/linux/kvm_types.h              |  1 +
>  virt/kvm/kvm_main.c                    | 52 +++++++++++++++++++-------
>  9 files changed, 63 insertions(+), 22 deletions(-)
> 

You declare ioremap_cache_force() arch/x86/include/asm/io.h  in and
define it in arch/x86/mm/ioremap.c which is architecture specific code,
but use it in __kvm_map_gfn() in virt/kvm/kvm_main.c which is common
code.

Thus your series breaks the build for the s390 architecture. Have you
tried to (cross) compile for s390?

Regards,
Halil