KVM: x86: SYSCALL cannot clear eflags[1]

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@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 713295d..e475cdf 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2306,6 +2306,7 @@ 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 */