leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

KVM: x86: allow RSM from 64-bit mode

Browse Source 
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: 660a5d517a
Tested-by: Laszlo Ersek <lersek@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-11-03 13:43:05 +01:00
parent 656ec4a492
commit 89651a3dec
1 changed files with 25 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
arch/x86/kvm/emulate.c
View File

@ -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),