From: Greg KH <[email protected]> 3.5-stable review patch. If anyone has any objections, please let me know.
------------------ From: Avi Kivity <[email protected]> (cherry picked from commit aa67f6096c19bcdb1951ef88be3cf3d2118809dc) Commit b2da15ac26a0c ("KVM: VMX: Optimize %ds, %es reload") broke i386 in the following scenario: vcpu_load ... vmx_save_host_state vmx_vcpu_run (ds.rpl, es.rpl cleared by hardware) interrupt push ds, es # pushes bad ds, es schedule vmx_vcpu_put vmx_load_host_state reload ds, es (with __USER_DS) pop ds, es # of other thread's stack iret # other thread runs interrupt push ds, es schedule # back in vcpu thread pop ds, es # now with rpl=0 iret ... vcpu_put resume_userspace iret # clears ds, es due to mismatched rpl (instead of resume_userspace, we might return with SYSEXIT and then take an exception; when the exception IRETs we end up with cleared ds, es) Fix by avoiding the optimization on i386 and reloading ds, es on the lightweight exit path. Reported-by: Chris Clayron <[email protected]> Signed-off-by: Avi Kivity <[email protected]> Signed-off-by: Marcelo Tosatti <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/kvm/vmx.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1470,13 +1470,6 @@ static void __vmx_load_host_state(struct loadsegment(ds, vmx->host_state.ds_sel); loadsegment(es, vmx->host_state.es_sel); } -#else - /* - * The sysexit path does not restore ds/es, so we must set them to - * a reasonable value ourselves. - */ - loadsegment(ds, __USER_DS); - loadsegment(es, __USER_DS); #endif reload_tss(); #ifdef CONFIG_X86_64 @@ -6273,6 +6266,19 @@ static void __noclone vmx_vcpu_run(struc #endif ); +#ifndef CONFIG_X86_64 + /* + * The sysexit path does not restore ds/es, so we must set them to + * a reasonable value ourselves. + * + * We can't defer this to vmx_load_host_state() since that function + * may be executed in interrupt context, which saves and restore segments + * around it, nullifying its effect. + */ + loadsegment(ds, __USER_DS); + loadsegment(es, __USER_DS); +#endif + vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP) | (1 << VCPU_EXREG_RFLAGS) | (1 << VCPU_EXREG_CPL) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
