• Brijesh Singh's avatar
    x86/mm: Add .bss..decrypted section to hold shared variables · b3f0907c
    Brijesh Singh authored
    kvmclock defines few static variables which are shared with the
    hypervisor during the kvmclock initialization.
    
    When SEV is active, memory is encrypted with a guest-specific key, and
    if the guest OS wants to share the memory region with the hypervisor
    then it must clear the C-bit before sharing it.
    
    Currently, we use kernel_physical_mapping_init() to split large pages
    before clearing the C-bit on shared pages. But it fails when called from
    the kvmclock initialization (mainly because the memblock allocator is
    not ready that early during boot).
    
    Add a __bss_decrypted section attribute which can be used when defining
    such shared variable. The so-defined variables will be placed in the
    .bss..decrypted section. This section will be mapped with C=0 early
    during boot.
    
    The .bss..decrypted section has a big chunk of memory that may be unused
    when memory encryption is not active, free it when memory encryption is
    not active.
    Suggested-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarBrijesh Singh <brijesh.singh@amd.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: Tom Lendacky <thomas.lendacky@amd.com>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Sean Christopherson <sean.j.christopherson@intel.com>
    Cc: Radim Krčmář<rkrcmar@redhat.com>
    Cc: kvm@vger.kernel.org
    Link: https://lkml.kernel.org/r/1536932759-12905-2-git-send-email-brijesh.singh@amd.com
    b3f0907c
head64.c 12.8 KB