KVM: task switch: use seg regs provided by subarch instead of reading from GDT

(cherry-picked from commit 34198bf8426276a2ce1e97056a0f02d43637e5ae)

There is no guarantee that the old TSS descriptor in the GDT contains
the proper base address. This is the case for Windows installation's
reboot-via-triplefault.

Use guest registers instead. Also translate the address properly.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b210579c856208bde99105bff77e074ae366137c..1be4512cc09a5a4c5e423f1ef3eed2a52ef76f70 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3251,54 +3251,6 @@ static u32 get_tss_base_addr(struct kvm_vcpu *vcpu,
        return vcpu->arch.mmu.gva_to_gpa(vcpu, base_addr);
 }
 
-static int load_tss_segment32(struct kvm_vcpu *vcpu,
-                             struct desc_struct *seg_desc,
-                             struct tss_segment_32 *tss)
-{
-       u32 base_addr;
-
-       base_addr = get_tss_base_addr(vcpu, seg_desc);
-
-       return kvm_read_guest(vcpu->kvm, base_addr, tss,
-                             sizeof(struct tss_segment_32));
-}
-
-static int save_tss_segment32(struct kvm_vcpu *vcpu,
-                             struct desc_struct *seg_desc,
-                             struct tss_segment_32 *tss)
-{
-       u32 base_addr;
-
-       base_addr = get_tss_base_addr(vcpu, seg_desc);
-
-       return kvm_write_guest(vcpu->kvm, base_addr, tss,
-                              sizeof(struct tss_segment_32));
-}
-
-static int load_tss_segment16(struct kvm_vcpu *vcpu,
-                             struct desc_struct *seg_desc,
-                             struct tss_segment_16 *tss)
-{
-       u32 base_addr;
-
-       base_addr = get_tss_base_addr(vcpu, seg_desc);
-
-       return kvm_read_guest(vcpu->kvm, base_addr, tss,
-                             sizeof(struct tss_segment_16));
-}
-
-static int save_tss_segment16(struct kvm_vcpu *vcpu,
-                             struct desc_struct *seg_desc,
-                             struct tss_segment_16 *tss)
-{
-       u32 base_addr;
-
-       base_addr = get_tss_base_addr(vcpu, seg_desc);
-
-       return kvm_write_guest(vcpu->kvm, base_addr, tss,
-                              sizeof(struct tss_segment_16));
-}
-
 static u16 get_segment_selector(struct kvm_vcpu *vcpu, int seg)
 {
        struct kvm_segment kvm_seg;
@@ -3456,20 +3408,26 @@ static int load_state_from_tss16(struct kvm_vcpu *vcpu,
 }
 
 int kvm_task_switch_16(struct kvm_vcpu *vcpu, u16 tss_selector,
-                      struct desc_struct *cseg_desc,
+                      u32 old_tss_base,
                       struct desc_struct *nseg_desc)
 {
        struct tss_segment_16 tss_segment_16;
        int ret = 0;
 
-       if (load_tss_segment16(vcpu, cseg_desc, &tss_segment_16))
+       if (kvm_read_guest(vcpu->kvm, old_tss_base, &tss_segment_16,
+                          sizeof tss_segment_16))
                goto out;
 
        save_state_to_tss16(vcpu, &tss_segment_16);
-       save_tss_segment16(vcpu, cseg_desc, &tss_segment_16);
 
-       if (load_tss_segment16(vcpu, nseg_desc, &tss_segment_16))
+       if (kvm_write_guest(vcpu->kvm, old_tss_base, &tss_segment_16,
+                           sizeof tss_segment_16))
                goto out;
+
+       if (kvm_read_guest(vcpu->kvm, get_tss_base_addr(vcpu, nseg_desc),
+                          &tss_segment_16, sizeof tss_segment_16))
+               goto out;
+
        if (load_state_from_tss16(vcpu, &tss_segment_16))
                goto out;
 
@@ -3479,20 +3437,26 @@ out:
 }
 
 int kvm_task_switch_32(struct kvm_vcpu *vcpu, u16 tss_selector,
-                      struct desc_struct *cseg_desc,
+                      u32 old_tss_base,
                       struct desc_struct *nseg_desc)
 {
        struct tss_segment_32 tss_segment_32;
        int ret = 0;
 
-       if (load_tss_segment32(vcpu, cseg_desc, &tss_segment_32))
+       if (kvm_read_guest(vcpu->kvm, old_tss_base, &tss_segment_32,
+                          sizeof tss_segment_32))
                goto out;
 
        save_state_to_tss32(vcpu, &tss_segment_32);
-       save_tss_segment32(vcpu, cseg_desc, &tss_segment_32);
 
-       if (load_tss_segment32(vcpu, nseg_desc, &tss_segment_32))
+       if (kvm_write_guest(vcpu->kvm, old_tss_base, &tss_segment_32,
+                           sizeof tss_segment_32))
+               goto out;
+
+       if (kvm_read_guest(vcpu->kvm, get_tss_base_addr(vcpu, nseg_desc),
+                          &tss_segment_32, sizeof tss_segment_32))
                goto out;
+
        if (load_state_from_tss32(vcpu, &tss_segment_32))
                goto out;
 
@@ -3507,16 +3471,20 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason)
        struct desc_struct cseg_desc;
        struct desc_struct nseg_desc;
        int ret = 0;
+       u32 old_tss_base = get_segment_base(vcpu, VCPU_SREG_TR);
+       u16 old_tss_sel = get_segment_selector(vcpu, VCPU_SREG_TR);
 
-       get_segment(vcpu, &tr_seg, VCPU_SREG_TR);
+       old_tss_base = vcpu->arch.mmu.gva_to_gpa(vcpu, old_tss_base);
 
+       /* FIXME: Handle errors. Failure to read either TSS or their
+        * descriptors should generate a pagefault.
+        */
        if (load_guest_segment_descriptor(vcpu, tss_selector, &nseg_desc))
                goto out;
 
-       if (load_guest_segment_descriptor(vcpu, tr_seg.selector, &cseg_desc))
+       if (load_guest_segment_descriptor(vcpu, old_tss_sel, &cseg_desc))
                goto out;
 
-
        if (reason != TASK_SWITCH_IRET) {
                int cpl;
 
@@ -3534,8 +3502,7 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason)
 
        if (reason == TASK_SWITCH_IRET || reason == TASK_SWITCH_JMP) {
                cseg_desc.type &= ~(1 << 1); //clear the B flag
-               save_guest_segment_descriptor(vcpu, tr_seg.selector,
-                                             &cseg_desc);
+               save_guest_segment_descriptor(vcpu, old_tss_sel, &cseg_desc);
        }
 
        if (reason == TASK_SWITCH_IRET) {
@@ -3547,10 +3514,10 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int reason)
        kvm_x86_ops->cache_regs(vcpu);
 
        if (nseg_desc.type & 8)
-               ret = kvm_task_switch_32(vcpu, tss_selector, &cseg_desc,
+               ret = kvm_task_switch_32(vcpu, tss_selector, old_tss_base,
                                         &nseg_desc);
        else
-               ret = kvm_task_switch_16(vcpu, tss_selector, &cseg_desc,
+               ret = kvm_task_switch_16(vcpu, tss_selector, old_tss_base,
                                         &nseg_desc);
 
        if (reason == TASK_SWITCH_CALL || reason == TASK_SWITCH_GATE) {