diff options
| author | Avi Kivity <avi@redhat.com> | 2012-08-01 15:48:03 +0200 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2012-08-02 01:23:57 +0200 |
| commit | aa67f6096c19bcdb1951ef88be3cf3d2118809dc (patch) | |
| tree | 61a806e065b9db4eabfd85753333e580d8b0a465 | |
| parent | KVM: x86: apply kvmclock offset to guest wall clock time (diff) | |
| download | linux-aa67f6096c19bcdb1951ef88be3cf3d2118809dc.tar.xz linux-aa67f6096c19bcdb1951ef88be3cf3d2118809dc.zip | |
KVM: VMX: Fix ds/es corruption on i386 with preemption
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 <chris2553@googlemail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
| -rw-r--r-- | arch/x86/kvm/vmx.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index c39b60707e02..c00f03de1b79 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1488,13 +1488,6 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx) 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 @@ -6370,6 +6363,19 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) #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) |