diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2015-11-03 13:43:05 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2015-11-04 16:24:38 +0100 |
| commit | 89651a3decbe03754f304a0b248f27eeb9a37937 (patch) | |
| tree | 9a97a14cb71b3695b8da048829bddfa3ad5d2dee | |
| parent | 656ec4a4928a3db7d16e5cb9bce351a478cfd3d5 (diff) | |
KVM: x86: allow RSM from 64-bit mode
The SDM says that exiting system management mode from 64-bit mode
is invalid, but that would be too good to be true. But actually,
most of the code is already there to support exiting from compat
mode (EFER.LME=1, EFER.LMA=0). Getting all the way from 64-bit
mode to real mode only requires clearing CS.L and CR4.PCIDE.
Cc: stable@vger.kernel.org
Fixes: 660a5d517aaab9187f93854425c4c63f4a09195c
Tested-by: Laszlo Ersek <lersek@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/emulate.c | 30 |
1 files changed, 25 insertions, 5 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index b60fed56671b..1505587d06e9 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2484,16 +2484,36 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt) /* * Get back to real mode, to prepare a safe state in which to load - * CR0/CR3/CR4/EFER. - * - * CR4.PCIDE must be zero, because it is a 64-bit mode only feature. + * CR0/CR3/CR4/EFER. It's all a bit more complicated if the vCPU + * supports long mode. */ + cr4 = ctxt->ops->get_cr(ctxt, 4); + if (emulator_has_longmode(ctxt)) { + struct desc_struct cs_desc; + + /* Zero CR4.PCIDE before CR0.PG. */ + if (cr4 & X86_CR4_PCIDE) { + ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PCIDE); + cr4 &= ~X86_CR4_PCIDE; + } + + /* A 32-bit code segment is required to clear EFER.LMA. */ + memset(&cs_desc, 0, sizeof(cs_desc)); + cs_desc.type = 0xb; + cs_desc.s = cs_desc.g = cs_desc.p = 1; + ctxt->ops->set_segment(ctxt, 0, &cs_desc, 0, VCPU_SREG_CS); + } + + /* For the 64-bit case, this will clear EFER.LMA. */ cr0 = ctxt->ops->get_cr(ctxt, 0); if (cr0 & X86_CR0_PE) ctxt->ops->set_cr(ctxt, 0, cr0 & ~(X86_CR0_PG | X86_CR0_PE)); - cr4 = ctxt->ops->get_cr(ctxt, 4); + + /* Now clear CR4.PAE (which must be done before clearing EFER.LME). */ if (cr4 & X86_CR4_PAE) ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PAE); + + /* And finally go back to 32-bit mode. */ efer = 0; ctxt->ops->set_msr(ctxt, MSR_EFER, efer); @@ -4454,7 +4474,7 @@ static const struct opcode twobyte_table[256] = { F(DstMem | SrcReg | Src2CL | ModRM, em_shld), N, N, /* 0xA8 - 0xAF */ I(Stack | Src2GS, em_push_sreg), I(Stack | Src2GS, em_pop_sreg), - II(No64 | EmulateOnUD | ImplicitOps, em_rsm, rsm), + II(EmulateOnUD | ImplicitOps, em_rsm, rsm), F(DstMem | SrcReg | ModRM | BitOp | Lock | PageTable, em_bts), F(DstMem | SrcReg | Src2ImmByte | ModRM, em_shrd), F(DstMem | SrcReg | Src2CL | ModRM, em_shrd), |