Re: Current mainline kernel FTBFS in KVM SEV

[Uros Bizjak <ubizjak@gmail.com>]

On Thu, Apr 9, 2020 at 10:33 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 09/04/20 10:20, Uros Bizjak wrote:
> > Current mainline kernel fails to build (on Fedora 31) with:
> >
> >   GEN     .version
> >   CHK     include/generated/compile.h
> >   LD      vmlinux.o
> >   MODPOST vmlinux.o
> >   MODINFO modules.builtin.modinfo
> >   GEN     modules.builtin
> >   LD      .tmp_vmlinux.btf
> > ld: arch/x86/kvm/svm/sev.o: in function `sev_flush_asids':
> > /hdd/uros/git/linux/arch/x86/kvm/svm/sev.c:48: undefined reference to
> > `sev_guest_df_flush'
> > ld: arch/x86/kvm/svm/sev.o: in function `sev_hardware_setup':
> > /hdd/uros/git/linux/arch/x86/kvm/svm/sev.c:1146: undefined reference
> > to `sev_platform_status'
> >   BTF     .btf.vmlinux.bin.o
>
> Strange, the functions are defined and exported with
> CONFIG_CRYPTO_DEV_SP_PSP, which is "y" in your config.

The problem is with

CONFIG_CRYPTO_DEV_CCP_DD=m

in combination with

CONFIG_KVM_AMD=y

in arch/x86/kvmKconfig, there is:

--cut here--
config KVM_AMD_SEV
    def_bool y
    bool "AMD Secure Encrypted Virtualization (SEV) support"
    depends on KVM_AMD && X86_64
    depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
    ---help---
    Provides support for launching Encrypted VMs on AMD processors.
--cut here--

which doesn't disable the compilation of sev.o. The missing functions
are actually in ccp.o *module*, called from built-in functions of
sev.o

Enabling CRYPTO_DEV_CCP_DD=y as a built-in instead of a module fixes the build.

Uros.