Commit 5bea5123cbf0 ("KVM: VMX: check nested state and CR4.VMXE against
SMM") introduced a check to vmx_set_cr4() forbidding to set VMXE from SMM.
The check is correct, however, there is a special case when RSM is called
to leave SMM: rsm_enter_protected_mode() is called with HF_SMM_MASK still
set and in case VMXE was set before entering SMM we're failing to return.
Resolve the issue by temporary dropping HF_SMM_MASK around set_cr4() calls
when ops->set_cr() is called from RSM.
Reported-by: Jon Doron <ari...@gmail.com>
Suggested-by: Liran Alon <liran.a...@oracle.com>
Fixes: 5bea5123cbf0 ("KVM: VMX: check nested state and CR4.VMXE against SMM")
Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
- Instread of putting the temporary HF_SMM_MASK drop to
rsm_enter_protected_mode() (as was suggested by Liran), move it to
emulator_set_cr() modifying its interface. emulate.c seems to be
vcpu-specifics-free at this moment, we may want to keep it this way.
- It seems that Hyper-V+UEFI on KVM is still broken, I'm observing sporadic
hangs even with this patch. These hangs, however, seem to be unrelated to
rsm.
---
arch/x86/include/asm/kvm_emulate.h | 3 ++-
arch/x86/kvm/emulate.c | 27 ++++++++++++++-------------
arch/x86/kvm/x86.c | 12 +++++++++++-
3 files changed, 27 insertions(+), 15 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h
b/arch/x86/include/asm/kvm_emulate.h
index 93c4bf598fb0..6c33caa82fa5 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -203,7 +203,8 @@ struct x86_emulate_ops {
void (*set_gdt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
void (*set_idt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
ulong (*get_cr)(struct x86_emulate_ctxt *ctxt, int cr);
- int (*set_cr)(struct x86_emulate_ctxt *ctxt, int cr, ulong val);
+ int (*set_cr)(struct x86_emulate_ctxt *ctxt, int cr, ulong val,
+ bool from_rsm);
int (*cpl)(struct x86_emulate_ctxt *ctxt);
int (*get_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong *dest);
int (*set_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong value);
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index c338984c850d..a6204105d4d7 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2413,7 +2413,7 @@ static int rsm_enter_protected_mode(struct
x86_emulate_ctxt *ctxt,
cr3 &= ~0xfff;
}
- bad = ctxt->ops->set_cr(ctxt, 3, cr3);
+ bad = ctxt->ops->set_cr(ctxt, 3, cr3, true);
if (bad)
return X86EMUL_UNHANDLEABLE;
@@ -2422,20 +2422,20 @@ static int rsm_enter_protected_mode(struct
x86_emulate_ctxt *ctxt,
* Then enable protected mode. However, PCID cannot be enabled
* if EFER.LMA=0, so set it separately.
*/
- bad = ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PCIDE);
+ bad = ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PCIDE, true);
if (bad)
return X86EMUL_UNHANDLEABLE;
- bad = ctxt->ops->set_cr(ctxt, 0, cr0);
+ bad = ctxt->ops->set_cr(ctxt, 0, cr0, true);
if (bad)
return X86EMUL_UNHANDLEABLE;
if (cr4 & X86_CR4_PCIDE) {
- bad = ctxt->ops->set_cr(ctxt, 4, cr4);
+ bad = ctxt->ops->set_cr(ctxt, 4, cr4, true);
if (bad)
return X86EMUL_UNHANDLEABLE;
if (pcid) {
- bad = ctxt->ops->set_cr(ctxt, 3, cr3 | pcid);
+ bad = ctxt->ops->set_cr(ctxt, 3, cr3 | pcid, true);
if (bad)
return X86EMUL_UNHANDLEABLE;
}
@@ -2581,7 +2581,7 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
/* Zero CR4.PCIDE before CR0.PG. */
if (cr4 & X86_CR4_PCIDE) {
- ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PCIDE);
+ ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PCIDE, true);
cr4 &= ~X86_CR4_PCIDE;
}
@@ -2595,11 +2595,12 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
/* 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));
+ ctxt->ops->set_cr(ctxt, 0, cr0 & ~(X86_CR0_PG | X86_CR0_PE),
+ true);
/* 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);
+ ctxt->ops->set_cr(ctxt, 4, cr4 & ~X86_CR4_PAE, true);
/* And finally go back to 32-bit mode. */
efer = 0;
@@ -3131,7 +3132,7 @@ static int load_state_from_tss32(struct x86_emulate_ctxt
*ctxt,
int ret;
u8 cpl;
- if (ctxt->ops->set_cr(ctxt, 3, tss->cr3))
+ if (ctxt->ops->set_cr(ctxt, 3, tss->cr3, false))
return emulate_gp(ctxt, 0);
ctxt->_eip = tss->eip;
ctxt->eflags = tss->eflags | 2;
@@ -3331,7 +3332,7 @@ static int emulator_do_task_switch(struct
x86_emulate_ctxt *ctxt,
write_segment_descriptor(ctxt, tss_selector, &next_tss_desc);
}
- ops->set_cr(ctxt, 0, ops->get_cr(ctxt, 0) | X86_CR0_TS);
+ ops->set_cr(ctxt, 0, ops->get_cr(ctxt, 0) | X86_CR0_TS, false);
ops->set_segment(ctxt, tss_selector, &next_tss_desc, 0, VCPU_SREG_TR);
if (has_error_code) {
@@ -3633,7 +3634,7 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
static int em_cr_write(struct x86_emulate_ctxt *ctxt)
{
- if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val))
+ if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val, false))
return emulate_gp(ctxt, 0);
/* Disable writeback. */
@@ -3766,7 +3767,7 @@ static int em_clts(struct x86_emulate_ctxt *ctxt)
cr0 = ctxt->ops->get_cr(ctxt, 0);
cr0 &= ~X86_CR0_TS;
- ctxt->ops->set_cr(ctxt, 0, cr0);
+ ctxt->ops->set_cr(ctxt, 0, cr0, false);
return X86EMUL_CONTINUE;
}
@@ -3866,7 +3867,7 @@ static int em_smsw(struct x86_emulate_ctxt *ctxt)
static int em_lmsw(struct x86_emulate_ctxt *ctxt)
{
ctxt->ops->set_cr(ctxt, 0, (ctxt->ops->get_cr(ctxt, 0) & ~0x0eul)
- | (ctxt->src.val & 0x0f));
+ | (ctxt->src.val & 0x0f), false);
ctxt->dst.type = OP_NONE;
return X86EMUL_CONTINUE;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a419656521b6..f2745e3170b6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5739,7 +5739,8 @@ static unsigned long emulator_get_cr(struct
x86_emulate_ctxt *ctxt, int cr)
return value;
}
-static int emulator_set_cr(struct x86_emulate_ctxt *ctxt, int cr, ulong val)
+static int emulator_set_cr(struct x86_emulate_ctxt *ctxt, int cr, ulong val,
+ bool from_rsm)
{
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
int res = 0;
@@ -5755,7 +5756,16 @@ static int emulator_set_cr(struct x86_emulate_ctxt
*ctxt, int cr, ulong val)
res = kvm_set_cr3(vcpu, val);
break;
case 4:
+ /*
+ * set_cr4() may forbid to set certain flags (e.g. VMXE) from
+ * SMM but we're actually leaving it; temporary drop HF_SMM_MASK
+ * when setting CR4.
+ */
+ if (from_rsm)
+ vcpu->arch.hflags &= ~HF_SMM_MASK;
res = kvm_set_cr4(vcpu, mk_cr_64(kvm_read_cr4(vcpu), val));
+ if (from_rsm)
+ vcpu->arch.hflags |= HF_SMM_MASK;
break;
case 8:
res = kvm_set_cr8(vcpu, val);
--
2.20.1
