| Message ID | 20210202165546.2390296-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Update emulator context mode if SYSENTER xfers to 64-bit mode | expand |
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 56cae1ff9e3f..66a08322988f 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2879,6 +2879,8 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt) ops->get_msr(ctxt, MSR_IA32_SYSENTER_ESP, &msr_data); *reg_write(ctxt, VCPU_REGS_RSP) = (efer & EFER_LMA) ? msr_data : (u32)msr_data; + if (efer & EFER_LMA) + ctxt->mode = X86EMUL_MODE_PROT64; return X86EMUL_CONTINUE; }
Set the emulator context to PROT64 if SYSENTER transitions from 32-bit userspace (compat mode) to a 64-bit kernel, otherwise the RIP update at the end of x86_emulate_insn() will incorrectly truncate the new RIP. Note, this bug is mostly limited to running an Intel virtual CPU model on an AMD physical CPU, as other combinations of virtual and physical CPUs do not trigger full emulation. On Intel CPUs, SYSENTER in compatibility mode is legal, and unconditionally transitions to 64-bit mode. On AMD CPUs, SYSENTER is illegal in compatibility mode and #UDs. If the vCPU is AMD, KVM injects a #UD on SYSENTER in compat mode. If the pCPU is Intel, SYSENTER will execute natively and not trigger #UD->VM-Exit (ignoring guest TLB shenanigans). Fixes: fede8076aab4 ("KVM: x86: handle wrap around 32-bit address space") Cc: stable@vger.kernel.org Signed-off-by: Jonny Barker <jonny@jonnybarker.com> [sean: wrote changelog] Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/emulate.c | 2 ++ 1 file changed, 2 insertions(+)