Re: [RFCv2 14/16] KVM: Handle protected memory in __kvm_map_gfn()/__kvm_unmap_gfn()

[Halil Pasic]

On Tue, 20 Oct 2020 09:18:57 +0300
"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> ---
>  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