From 879ae1880449c88db11c1ebdaedc2da79b2fe73f Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Wed, 4 Nov 2015 12:54:41 +0100 Subject: [PATCH] KVM: x86: obey KVM_X86_QUIRK_CD_NW_CLEARED in kvm_set_cr0() Commit b18d5431acc7 ("KVM: x86: fix CR0.CD virtualization") was technically correct, but it broke OVMF guests by slowing down various parts of the firmware. Commit fb279950ba02 ("KVM: vmx: obey KVM_QUIRK_CD_NW_CLEARED") quirked the first function modified by b18d5431acc7, 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 b18d5431acc7, 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 b18d5431acc7. Fixes: b18d5431acc7a2fd22767925f3a6f597aa4bd29e Cc: stable@vger.kernel.org Cc: Jordan Justen Cc: Alex Williamson Reviewed-by: Xiao Guangrong Tested-by: Janusz Mocek Signed-off-by: Laszlo Ersek # Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a24bae0a83a2..30723a4122cd 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -625,7 +625,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) if ((cr0 ^ old_cr0) & update_bits) kvm_mmu_reset_context(vcpu); - if ((cr0 ^ old_cr0) & X86_CR0_CD) + if (((cr0 ^ old_cr0) & X86_CR0_CD) && + kvm_arch_has_noncoherent_dma(vcpu->kvm) && + !kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED)) kvm_zap_gfn_range(vcpu->kvm, 0, ~0ULL); return 0; -- 2.20.1