On 03/11/2015 19:34, Laszlo Ersek wrote:
> 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.
>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Jordan Justen <[email protected]>
> Cc: Janusz Mocek <[email protected]>
> Cc: Alex Williamson <[email protected]>
> Cc: Xiao Guangrong <[email protected]>
> Signed-off-by: Laszlo Ersek <[email protected]>
> ---
> 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 a24bae0..30723a4 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;
>
Applied, thanks.
Paolo
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