On 02/11/2015 22:20, Radim Krčmář wrote:
> The comment in code had it mostly right, but we enable paging for
> emulated real mode regardless of EPT.
>
> Without EPT (which implies emulated real mode), secondary VCPUs won't
> start unless we disable SM[AE]P when the guest doesn't use paging.
>
> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index b680c2e0e8a3..ab598558a7a4 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3788,20 +3788,21 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
> if (!is_paging(vcpu)) {
> hw_cr4 &= ~X86_CR4_PAE;
> hw_cr4 |= X86_CR4_PSE;
> - /*
> - * SMEP/SMAP is disabled if CPU is in non-paging mode
> - * in hardware. However KVM always uses paging mode to
> - * emulate guest non-paging mode with TDP.
> - * To emulate this behavior, SMEP/SMAP needs to be
> - * manually disabled when guest switches to non-paging
> - * mode.
> - */
> - hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP);
> } else if (!(cr4 & X86_CR4_PAE)) {
> hw_cr4 &= ~X86_CR4_PAE;
> }
> }
>
> + if (!enable_unrestricted_guest && !is_paging(vcpu))
> + /*
> + * SMEP/SMAP is disabled if CPU is in non-paging mode in
> + * hardware. However KVM always uses paging mode without
> + * unrestricted guest.
> + * To emulate this behavior, SMEP/SMAP needs to be manually
> + * disabled when guest switches to non-paging mode.
> + */
> + hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP);
> +
> vmcs_writel(CR4_READ_SHADOW, cr4);
> vmcs_writel(GUEST_CR4, hw_cr4);
> return 0;
>
Applied with Cc: stable@xxxxxxxxxxxxxxx.
Paolo
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