KVM: VMX: Fix KVM_SET_SREGS with big real mode segmentslinux-3.5.y

For example migration between Westmere and Nehelem hosts, caught in big real mode.

The code that fixes the segments for real mode guest was moved from enter_rmode
to vmx_set_segments. enter_rmode calls vmx_set_segments for each segment.

Signed-off-by: Orit Wasserman <owasserm@rehdat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
(cherry picked from commit b246dd5df139501b974bd6b28f7815e53b3a792f)

1 files changed, 58 insertions, 12 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 61593fd19c4262..86c8704e92a531 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -615,6 +615,10 @@ static void kvm_cpu_vmxon(u64 addr);
 static void kvm_cpu_vmxoff(void);
 static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
 static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr);
+static void vmx_set_segment(struct kvm_vcpu *vcpu,
+			    struct kvm_segment *var, int seg);
+static void vmx_get_segment(struct kvm_vcpu *vcpu,
+			    struct kvm_segment *var, int seg);
 
 static DEFINE_PER_CPU(struct vmcs *, vmxarea);
 static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
@@ -2763,6 +2767,7 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 {
 	unsigned long flags;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	struct kvm_segment var;
 
 	if (enable_unrestricted_guest)
 		return;
@@ -2806,20 +2811,23 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 	if (emulate_invalid_guest_state)
 		goto continue_rmode;
 
-	vmcs_write16(GUEST_SS_SELECTOR, vmcs_readl(GUEST_SS_BASE) >> 4);
-	vmcs_write32(GUEST_SS_LIMIT, 0xffff);
-	vmcs_write32(GUEST_SS_AR_BYTES, 0xf3);
+	vmx_get_segment(vcpu, &var, VCPU_SREG_SS);
+	vmx_set_segment(vcpu, &var, VCPU_SREG_SS);
+
+	vmx_get_segment(vcpu, &var, VCPU_SREG_CS);
+	vmx_set_segment(vcpu, &var, VCPU_SREG_CS);
+
+	vmx_get_segment(vcpu, &var, VCPU_SREG_ES);
+	vmx_set_segment(vcpu, &var, VCPU_SREG_ES);
 
-	vmcs_write32(GUEST_CS_AR_BYTES, 0xf3);
-	vmcs_write32(GUEST_CS_LIMIT, 0xffff);
-	if (vmcs_readl(GUEST_CS_BASE) == 0xffff0000)
-		vmcs_writel(GUEST_CS_BASE, 0xf0000);
-	vmcs_write16(GUEST_CS_SELECTOR, vmcs_readl(GUEST_CS_BASE) >> 4);
+	vmx_get_segment(vcpu, &var, VCPU_SREG_DS);
+	vmx_set_segment(vcpu, &var, VCPU_SREG_DS);
 
-	fix_rmode_seg(VCPU_SREG_ES, &vmx->rmode.es);
-	fix_rmode_seg(VCPU_SREG_DS, &vmx->rmode.ds);
-	fix_rmode_seg(VCPU_SREG_GS, &vmx->rmode.gs);
-	fix_rmode_seg(VCPU_SREG_FS, &vmx->rmode.fs);
+	vmx_get_segment(vcpu, &var, VCPU_SREG_GS);
+	vmx_set_segment(vcpu, &var, VCPU_SREG_GS);
+
+	vmx_get_segment(vcpu, &var, VCPU_SREG_FS);
+	vmx_set_segment(vcpu, &var, VCPU_SREG_FS);
 
 continue_rmode:
 	kvm_mmu_reset_context(vcpu);
@@ -3222,6 +3230,44 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
 
 	vmcs_write32(sf->ar_bytes, ar);
 	__clear_bit(VCPU_EXREG_CPL, (ulong *)&vcpu->arch.regs_avail);
+
+	/*
+	 * Fix segments for real mode guest in hosts that don't have
+	 * "unrestricted_mode" or it was disabled.
+	 * This is done to allow migration of the guests from hosts with
+	 * unrestricted guest like Westmere to older host that don't have
+	 * unrestricted guest like Nehelem.
+	 */
+	if (!enable_unrestricted_guest && vmx->rmode.vm86_active) {
+		switch (seg) {
+		case VCPU_SREG_CS:
+			vmcs_write32(GUEST_CS_AR_BYTES, 0xf3);
+			vmcs_write32(GUEST_CS_LIMIT, 0xffff);
+			if (vmcs_readl(GUEST_CS_BASE) == 0xffff0000)
+				vmcs_writel(GUEST_CS_BASE, 0xf0000);
+			vmcs_write16(GUEST_CS_SELECTOR,
+				     vmcs_readl(GUEST_CS_BASE) >> 4);
+			break;
+		case VCPU_SREG_ES:
+			fix_rmode_seg(VCPU_SREG_ES, &vmx->rmode.es);
+			break;
+		case VCPU_SREG_DS:
+			fix_rmode_seg(VCPU_SREG_DS, &vmx->rmode.ds);
+			break;
+		case VCPU_SREG_GS:
+			fix_rmode_seg(VCPU_SREG_GS, &vmx->rmode.gs);
+			break;
+		case VCPU_SREG_FS:
+			fix_rmode_seg(VCPU_SREG_FS, &vmx->rmode.fs);
+			break;
+		case VCPU_SREG_SS:
+			vmcs_write16(GUEST_SS_SELECTOR,
+				     vmcs_readl(GUEST_SS_BASE) >> 4);
+			vmcs_write32(GUEST_SS_LIMIT, 0xffff);
+			vmcs_write32(GUEST_SS_AR_BYTES, 0xf3);
+			break;
+		}
+	}
 }
 
 static void vmx_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l)