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KVM: x86/emulator: Defer not-present segment check in __load_segment_descriptor()

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Per Intel's SDM on the "Instruction Set Reference", when
loading segment descriptor, not-present segment check should
be after all type and privilege checks. But the emulator checks
it first, then #NP is triggered instead of #GP if privilege fails
and segment is not present. Put not-present segment check after
type and privilege checks in __load_segment_descriptor().

Fixes: 38ba30ba51a00 (KVM: x86 emulator: Emulate task switch in emulator.c)
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Message-Id: <52573c01d369f506cadcf7233812427cf7db81a7.1644292363.git.houwenlong.hwl@antgroup.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Hou Wenlong 2022-02-08 17:34:03 +08:00 committed by Paolo Bonzini
parent 85c68eb429
commit ca85f00225
1 changed files with 9 additions and 5 deletions
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14
arch/x86/kvm/emulate.c
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@ -1608,11 +1608,6 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
goto exception;
}
if (!seg_desc.p) {
err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;
goto exception;
}
dpl = seg_desc.dpl;
switch (seg) {
@ -1652,6 +1647,10 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
case VCPU_SREG_TR:
if (seg_desc.s || (seg_desc.type != 1 && seg_desc.type != 9))
goto exception;
if (!seg_desc.p) {
err_vec = NP_VECTOR;
goto exception;
}
old_desc = seg_desc;
seg_desc.type |= 2; /* busy */
ret = ctxt->ops->cmpxchg_emulated(ctxt, desc_addr, &old_desc, &seg_desc,
@ -1676,6 +1675,11 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
break;
}
if (!seg_desc.p) {
err_vec = (seg == VCPU_SREG_SS) ? SS_VECTOR : NP_VECTOR;
goto exception;
}
if (seg_desc.s) {
/* mark segment as accessed */
if (!(seg_desc.type & 1)) {