• Laszlo Ersek's avatar
    KVM: x86: obey KVM_X86_QUIRK_CD_NW_CLEARED in kvm_set_cr0() · 879ae188
    Laszlo Ersek authored
    Commit b18d5431 ("KVM: x86: fix CR0.CD virtualization") was
    technically correct, but it broke OVMF guests by slowing down various
    parts of the firmware.
    
    Commit fb279950 ("KVM: vmx: obey KVM_QUIRK_CD_NW_CLEARED") quirked the
    first function modified by b18d5431, vmx_get_mt_mask(), for OVMF's
    sake. This restored the speed of the OVMF code that runs before
    PlatformPei (including the memory intensive LZMA decompression in SEC).
    
    This patch extends the quirk to the second function modified by
    b18d5431, kvm_set_cr0(). It eliminates the intrusive slowdown that
    hits the EFI_MP_SERVICES_PROTOCOL implementation of edk2's
    UefiCpuPkg/CpuDxe -- which is built into OVMF --, when CpuDxe starts up
    all APs at once for initialization, in order to count them.
    
    We also carry over the kvm_arch_has_noncoherent_dma() sub-condition from
    the other half of the original commit b18d5431.
    
    Fixes: b18d5431
    Cc: stable@vger.kernel.org
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Alex Williamson <alex.williamson@redhat.com>
    Reviewed-by: default avatarXiao Guangrong <guangrong.xiao@linux.intel.com>
    Tested-by: default avatarJanusz Mocek <januszmk6@gmail.com>
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>#
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    879ae188
x86.c 208 KB