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KVM: SVM: Keep intercepting task switching with NPT enabled 

AMD processors apparently have a bug in the hardware task switching
support when NPT is enabled. If the task switch triggers a NPF, we can
get wrong EXITINTINFO along with that fault. On resume, spurious
exceptions may then be injected into the guest.

We were able to reproduce this bug when our guest triggered #SS and the
handler were supposed to run over a separate task with not yet touched
stack pages.

Work around the issue by continuing to emulate task switches even in
NPT mode.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Jan Kiszka 2011-10-18 18:23:11 +02:00 committed by Avi Kivity
parent 7697e71f72
commit f1c1da2bde
1 changed files with 0 additions and 1 deletions
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arch/x86/kvm/svm.c
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@ -1084,7 +1084,6 @@ static void init_vmcb(struct vcpu_svm *svm)
if (npt_enabled) {
/* Setup VMCB for Nested Paging */
control->nested_ctl = 1;
clr_intercept(svm, INTERCEPT_TASK_SWITCH);
clr_intercept(svm, INTERCEPT_INVLPG);
clr_exception_intercept(svm, PF_VECTOR);
clr_cr_intercept(svm, INTERCEPT_CR3_READ);