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authorLadi Prosek <lprosek@redhat.com>2017-04-25 16:42:44 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-07-05 14:37:22 +0200
commitb9b3eb5c774eee256a33a6c0863ebad43a693353 (patch)
tree2717ec8e66698a20105afb9f1e822416d26e641b
parent3491a0b59fcd933ee6dac6e1ed320d76f16e2311 (diff)
KVM: x86: fix emulation of RSM and IRET instructions
commit 6ed071f051e12cf7baa1b69d3becb8f232fdfb7b upstream. On AMD, the effect of set_nmi_mask called by emulate_iret_real and em_rsm on hflags is reverted later on in x86_emulate_instruction where hflags are overwritten with ctxt->emul_flags (the kvm_set_hflags call). This manifests as a hang when rebooting Windows VMs with QEMU, OVMF, and >1 vcpu. Instead of trying to merge ctxt->emul_flags into vcpu->arch.hflags after an instruction is emulated, this commit deletes emul_flags altogether and makes the emulator access vcpu->arch.hflags using two new accessors. This way all changes, on the emulator side as well as in functions called from the emulator and accessing vcpu state with emul_to_vcpu, are preserved. More details on the bug and its manifestation with Windows and OVMF: It's a KVM bug in the interaction between SMI/SMM and NMI, specific to AMD. I believe that the SMM part explains why we started seeing this only with OVMF. KVM masks and unmasks NMI when entering and leaving SMM. When KVM emulates the RSM instruction in em_rsm, the set_nmi_mask call doesn't stick because later on in x86_emulate_instruction we overwrite arch.hflags with ctxt->emul_flags, effectively reverting the effect of the set_nmi_mask call. The AMD-specific hflag of interest here is HF_NMI_MASK. When rebooting the system, Windows sends an NMI IPI to all but the current cpu to shut them down. Only after all of them are parked in HLT will the initiating cpu finish the restart. If NMI is masked, other cpus never get the memo and the initiating cpu spins forever, waiting for hal!HalpInterruptProcessorsStarted to drop. That's the symptom we observe. Fixes: a584539b24b8 ("KVM: x86: pass the whole hflags field to emulator and back") Signed-off-by: Ladi Prosek <lprosek@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/include/asm/kvm_emulate.h4
-rw-r--r--arch/x86/kvm/emulate.c16
-rw-r--r--arch/x86/kvm/x86.c15
3 files changed, 24 insertions, 11 deletions
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index e9cd7befcb76..19d14ac23ef9 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -221,6 +221,9 @@ struct x86_emulate_ops {
void (*get_cpuid)(struct x86_emulate_ctxt *ctxt,
u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
+
+ unsigned (*get_hflags)(struct x86_emulate_ctxt *ctxt);
+ void (*set_hflags)(struct x86_emulate_ctxt *ctxt, unsigned hflags);
};
typedef u32 __attribute__((vector_size(16))) sse128_t;
@@ -290,7 +293,6 @@ struct x86_emulate_ctxt {
/* interruptibility state, as a result of execution of STI or MOV SS */
int interruptibility;
- int emul_flags;
bool perm_ok; /* do not check permissions if true */
bool ud; /* inject an #UD if host doesn't support insn */
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 1dcea225977d..04b2f3cad7ba 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2531,7 +2531,7 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
u64 smbase;
int ret;
- if ((ctxt->emul_flags & X86EMUL_SMM_MASK) == 0)
+ if ((ctxt->ops->get_hflags(ctxt) & X86EMUL_SMM_MASK) == 0)
return emulate_ud(ctxt);
/*
@@ -2580,11 +2580,11 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
return X86EMUL_UNHANDLEABLE;
}
- if ((ctxt->emul_flags & X86EMUL_SMM_INSIDE_NMI_MASK) == 0)
+ if ((ctxt->ops->get_hflags(ctxt) & X86EMUL_SMM_INSIDE_NMI_MASK) == 0)
ctxt->ops->set_nmi_mask(ctxt, false);
- ctxt->emul_flags &= ~X86EMUL_SMM_INSIDE_NMI_MASK;
- ctxt->emul_flags &= ~X86EMUL_SMM_MASK;
+ ctxt->ops->set_hflags(ctxt, ctxt->ops->get_hflags(ctxt) &
+ ~(X86EMUL_SMM_INSIDE_NMI_MASK | X86EMUL_SMM_MASK));
return X86EMUL_CONTINUE;
}
@@ -5296,6 +5296,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
const struct x86_emulate_ops *ops = ctxt->ops;
int rc = X86EMUL_CONTINUE;
int saved_dst_type = ctxt->dst.type;
+ unsigned emul_flags;
ctxt->mem_read.pos = 0;
@@ -5310,6 +5311,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
goto done;
}
+ emul_flags = ctxt->ops->get_hflags(ctxt);
if (unlikely(ctxt->d &
(No64|Undefined|Sse|Mmx|Intercept|CheckPerm|Priv|Prot|String))) {
if ((ctxt->mode == X86EMUL_MODE_PROT64 && (ctxt->d & No64)) ||
@@ -5343,7 +5345,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
fetch_possible_mmx_operand(ctxt, &ctxt->dst);
}
- if (unlikely(ctxt->emul_flags & X86EMUL_GUEST_MASK) && ctxt->intercept) {
+ if (unlikely(emul_flags & X86EMUL_GUEST_MASK) && ctxt->intercept) {
rc = emulator_check_intercept(ctxt, ctxt->intercept,
X86_ICPT_PRE_EXCEPT);
if (rc != X86EMUL_CONTINUE)
@@ -5372,7 +5374,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
goto done;
}
- if (unlikely(ctxt->emul_flags & X86EMUL_GUEST_MASK) && (ctxt->d & Intercept)) {
+ if (unlikely(emul_flags & X86EMUL_GUEST_MASK) && (ctxt->d & Intercept)) {
rc = emulator_check_intercept(ctxt, ctxt->intercept,
X86_ICPT_POST_EXCEPT);
if (rc != X86EMUL_CONTINUE)
@@ -5426,7 +5428,7 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
special_insn:
- if (unlikely(ctxt->emul_flags & X86EMUL_GUEST_MASK) && (ctxt->d & Intercept)) {
+ if (unlikely(emul_flags & X86EMUL_GUEST_MASK) && (ctxt->d & Intercept)) {
rc = emulator_check_intercept(ctxt, ctxt->intercept,
X86_ICPT_POST_MEMACCESS);
if (rc != X86EMUL_CONTINUE)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cba30e791e7d..88f914ea2db7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4999,6 +4999,16 @@ static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
kvm_x86_ops->set_nmi_mask(emul_to_vcpu(ctxt), masked);
}
+static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
+{
+ return emul_to_vcpu(ctxt)->arch.hflags;
+}
+
+static void emulator_set_hflags(struct x86_emulate_ctxt *ctxt, unsigned emul_flags)
+{
+ kvm_set_hflags(emul_to_vcpu(ctxt), emul_flags);
+}
+
static const struct x86_emulate_ops emulate_ops = {
.read_gpr = emulator_read_gpr,
.write_gpr = emulator_write_gpr,
@@ -5038,6 +5048,8 @@ static const struct x86_emulate_ops emulate_ops = {
.intercept = emulator_intercept,
.get_cpuid = emulator_get_cpuid,
.set_nmi_mask = emulator_set_nmi_mask,
+ .get_hflags = emulator_get_hflags,
+ .set_hflags = emulator_set_hflags,
};
static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask)
@@ -5090,7 +5102,6 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
BUILD_BUG_ON(HF_GUEST_MASK != X86EMUL_GUEST_MASK);
BUILD_BUG_ON(HF_SMM_MASK != X86EMUL_SMM_MASK);
BUILD_BUG_ON(HF_SMM_INSIDE_NMI_MASK != X86EMUL_SMM_INSIDE_NMI_MASK);
- ctxt->emul_flags = vcpu->arch.hflags;
init_decode_cache(ctxt);
vcpu->arch.emulate_regs_need_sync_from_vcpu = false;
@@ -5486,8 +5497,6 @@ restart:
unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
toggle_interruptibility(vcpu, ctxt->interruptibility);
vcpu->arch.emulate_regs_need_sync_to_vcpu = false;
- if (vcpu->arch.hflags != ctxt->emul_flags)
- kvm_set_hflags(vcpu, ctxt->emul_flags);
kvm_rip_write(vcpu, ctxt->eip);
if (r == EMULATE_DONE)
kvm_vcpu_check_singlestep(vcpu, rflags, &r);