KVM: x86: obey KVM_X86_QUIRK_CD_NW_CLEARED in kvm_set_cr0()

KVM: x86: obey KVM_X86_QUIRK_CD_NW_CLEARED in kvm_set_cr0()

Commit e35b37067b46 ("KVM: x86: fix CR0.CD virtualization") was
technically correct, but it broke OVMF guests by slowing down various
parts of the firmware.

Commit 482085ef8530 ("KVM: vmx: obey KVM_QUIRK_CD_NW_CLEARED") quirked the
first function modified by e35b37067b46, 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
e35b37067b46, 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 e35b37067b46.

Fixes: e35b37067b468defa4023d62489fc6498c115213
Cc: stable@vger.kernel.org
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Tested-by: Janusz Mocek <januszmk6@gmail.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>#
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>