SYSCALL emulation currently clears in 64-bit mode eflags according to
MSR_SYSCALL_MASK. However, on bare-metal eflags[1] which is fixed to one
cannot be cleared, even if MSR_SYSCALL_MASK masks the bit. This wrong behavior
may result in failed VM-entry, as VT disallows entry with eflags[1] cleared.
This patch sets the bit after masking eflags on syscall.
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index e624d62..f1484bb 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2286,6 +2286,7 @@ static int em_syscall(struct x86_emulate_ctxt *ctxt)
ops->get_msr(ctxt, MSR_SYSCALL_MASK, &msr_data);
ctxt->eflags &= ~msr_data;
+ ctxt->eflags |= EFLG_RESERVED_ONE_MASK;
#endif
} else {
/* legacy mode */
--
1.9.1
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