From eeadf9e7558ce2c34c0d91985d26047a6e2245e7 Mon Sep 17 00:00:00 2001 From: Nadav Har'El Date: Wed, 25 May 2011 23:14:38 +0300 Subject: [PATCH] KVM: nVMX: Handling of CR0 and CR4 modifying instructions When L2 tries to modify CR0 or CR4 (with mov or clts), and modifies a bit which L1 asked to shadow (via CR[04]_GUEST_HOST_MASK), we already do the right thing: we let L1 handle the trap (see nested_vmx_exit_handled_cr() in a previous patch). When L2 modifies bits that L1 doesn't care about, we let it think (via CR[04]_READ_SHADOW) that it did these modifications, while only changing (in GUEST_CR[04]) the bits that L0 doesn't shadow. This is needed for corect handling of CR0.TS for lazy FPU loading: L0 may want to leave TS on, while pretending to allow the guest to change it. Signed-off-by: Nadav Har'El Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/vmx.c | 58 +++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 55 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 1e6bd69ae433..6e9bebcdd5a6 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -4164,6 +4164,58 @@ vmx_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall) hypercall[2] = 0xc1; } +/* called to set cr0 as approriate for a mov-to-cr0 exit. */ +static int handle_set_cr0(struct kvm_vcpu *vcpu, unsigned long val) +{ + if (to_vmx(vcpu)->nested.vmxon && + ((val & VMXON_CR0_ALWAYSON) != VMXON_CR0_ALWAYSON)) + return 1; + + if (is_guest_mode(vcpu)) { + /* + * We get here when L2 changed cr0 in a way that did not change + * any of L1's shadowed bits (see nested_vmx_exit_handled_cr), + * but did change L0 shadowed bits. This can currently happen + * with the TS bit: L0 may want to leave TS on (for lazy fpu + * loading) while pretending to allow the guest to change it. + */ + if (kvm_set_cr0(vcpu, (val & vcpu->arch.cr0_guest_owned_bits) | + (vcpu->arch.cr0 & ~vcpu->arch.cr0_guest_owned_bits))) + return 1; + vmcs_writel(CR0_READ_SHADOW, val); + return 0; + } else + return kvm_set_cr0(vcpu, val); +} + +static int handle_set_cr4(struct kvm_vcpu *vcpu, unsigned long val) +{ + if (is_guest_mode(vcpu)) { + if (kvm_set_cr4(vcpu, (val & vcpu->arch.cr4_guest_owned_bits) | + (vcpu->arch.cr4 & ~vcpu->arch.cr4_guest_owned_bits))) + return 1; + vmcs_writel(CR4_READ_SHADOW, val); + return 0; + } else + return kvm_set_cr4(vcpu, val); +} + +/* called to set cr0 as approriate for clts instruction exit. */ +static void handle_clts(struct kvm_vcpu *vcpu) +{ + if (is_guest_mode(vcpu)) { + /* + * We get here when L2 did CLTS, and L1 didn't shadow CR0.TS + * but we did (!fpu_active). We need to keep GUEST_CR0.TS on, + * just pretend it's off (also in arch.cr0 for fpu_activate). + */ + vmcs_writel(CR0_READ_SHADOW, + vmcs_readl(CR0_READ_SHADOW) & ~X86_CR0_TS); + vcpu->arch.cr0 &= ~X86_CR0_TS; + } else + vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS)); +} + static int handle_cr(struct kvm_vcpu *vcpu) { unsigned long exit_qualification, val; @@ -4180,7 +4232,7 @@ static int handle_cr(struct kvm_vcpu *vcpu) trace_kvm_cr_write(cr, val); switch (cr) { case 0: - err = kvm_set_cr0(vcpu, val); + err = handle_set_cr0(vcpu, val); kvm_complete_insn_gp(vcpu, err); return 1; case 3: @@ -4188,7 +4240,7 @@ static int handle_cr(struct kvm_vcpu *vcpu) kvm_complete_insn_gp(vcpu, err); return 1; case 4: - err = kvm_set_cr4(vcpu, val); + err = handle_set_cr4(vcpu, val); kvm_complete_insn_gp(vcpu, err); return 1; case 8: { @@ -4206,7 +4258,7 @@ static int handle_cr(struct kvm_vcpu *vcpu) }; break; case 2: /* clts */ - vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS)); + handle_clts(vcpu); trace_kvm_cr_write(0, kvm_read_cr0(vcpu)); skip_emulated_instruction(vcpu); vmx_fpu_activate(vcpu); -- 2.30.2