KVM's "Lazy FPU loading" means that sometimes L0 needs to set CR0.TS, even if a guest didn't set it. Moreover, L0 must also trap CR0.TS changes and NM exceptions, even if we have a guest hypervisor (L1) who didn't want these traps. And of course, conversely: If L1 wanted to trap these events, we must let it, even if L0 is not interested in them.
This patch fixes some existing KVM code (in update_exception_bitmap(), vmx_fpu_activate(), vmx_fpu_deactivate()) to do the correct merging of L0's and L1's needs. Note that handle_cr() was already fixed in the above patch, and that new code in introduced in previous patches already handles CR0 correctly (see prepare_vmcs02(), prepare_vmcs12(), and nested_vmx_vmexit()). Signed-off-by: Nadav Har'El <[email protected]> --- arch/x86/kvm/vmx.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) --- .before/arch/x86/kvm/vmx.c 2011-05-16 22:36:50.000000000 +0300 +++ .after/arch/x86/kvm/vmx.c 2011-05-16 22:36:50.000000000 +0300 @@ -1179,6 +1179,15 @@ static void update_exception_bitmap(stru eb &= ~(1u << PF_VECTOR); /* bypass_guest_pf = 0 */ if (vcpu->fpu_active) eb &= ~(1u << NM_VECTOR); + + /* When we are running a nested L2 guest and L1 specified for it a + * certain exception bitmap, we must trap the same exceptions and pass + * them to L1. When running L2, we will only handle the exceptions + * specified above if L1 did not want them. + */ + if (is_guest_mode(vcpu)) + eb |= get_vmcs12(vcpu)->exception_bitmap; + vmcs_write32(EXCEPTION_BITMAP, eb); } @@ -1471,6 +1480,9 @@ static void vmx_fpu_activate(struct kvm_ vmcs_writel(GUEST_CR0, cr0); update_exception_bitmap(vcpu); vcpu->arch.cr0_guest_owned_bits = X86_CR0_TS; + if (is_guest_mode(vcpu)) + vcpu->arch.cr0_guest_owned_bits &= + ~get_vmcs12(vcpu)->cr0_guest_host_mask; vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits); } @@ -1494,12 +1506,29 @@ static inline unsigned long guest_readab static void vmx_fpu_deactivate(struct kvm_vcpu *vcpu) { + /* Note that there is no vcpu->fpu_active = 0 here. The caller must + * set this *before* calling this function. + */ vmx_decache_cr0_guest_bits(vcpu); vmcs_set_bits(GUEST_CR0, X86_CR0_TS | X86_CR0_MP); update_exception_bitmap(vcpu); vcpu->arch.cr0_guest_owned_bits = 0; vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits); - vmcs_writel(CR0_READ_SHADOW, vcpu->arch.cr0); + if (is_guest_mode(vcpu)) { + /* + * L1's specified read shadow might not contain the TS bit, + * so now that we turned on shadowing of this bit, we need to + * set this bit of the shadow. Like in nested_vmx_run we need + * guest_readable_cr0(vmcs12), but vmcs12->guest_cr0 is not + * yet up-to-date here because we just decached cr0.TS (and + * we'll only update vmcs12->guest_cr0 on nested exit). + */ + struct vmcs12 *vmcs12 = get_vmcs12(vcpu); + vmcs12->guest_cr0 = (vmcs12->guest_cr0 & ~X86_CR0_TS) | + (vcpu->arch.cr0 & X86_CR0_TS); + vmcs_writel(CR0_READ_SHADOW, guest_readable_cr0(vmcs12)); + } else + vmcs_writel(CR0_READ_SHADOW, vcpu->arch.cr0); } static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
