/* Shared #MC handler. */
void mcheck_cmn_handler(struct cpu_user_regs *regs, long error_code,
struct mca_banks *bankmask)
{
int xen_state_lost, dom0_state_lost, domU_state_lost;
struct vcpu *v = current;
struct domain *curdom = v->domain;
domid_t domid = curdom->domain_id;
int ctx_xen, ctx_dom0, ctx_domU;
uint32_t dom_state = DOM_NORMAL;
mctelem_cookie_t mctc = NULL;
struct mca_summary bs;
struct mc_info *mci = NULL;
int irqlocked = 0;
uint64_t gstatus;
int ripv;
/* This handler runs as interrupt gate. So IPIs from the
* polling service routine are defered until we're finished.
*/
/* Disable interrupts for the _vcpu_. It may not re-scheduled to
* another physical CPU. */
vcpu_schedule_lock_irq(v);
irqlocked = 1;
/* Read global status; if it does not indicate machine check
* in progress then bail as long as we have a valid ip to return to. */
gstatus = mca_rdmsr(MSR_IA32_MCG_STATUS);
ripv = ((gstatus & MCG_STATUS_RIPV) != 0);
if (!(gstatus & MCG_STATUS_MCIP) && ripv) {
add_taint(TAINT_MACHINE_CHECK); /* questionable */
vcpu_schedule_unlock_irq(v);
irqlocked = 0;
goto cmn_handler_done;
}
/* Go and grab error telemetry. We must choose whether to commit
* for logging or dismiss the cookie that is returned, and must not
* reference the cookie after that action.
*/
mctc = mcheck_mca_logout(MCA_MCE_HANDLER, bankmask, &bs, NULL);
if (mctc != NULL)
mci = (struct mc_info *)mctelem_dataptr(mctc);
/* Clear MCIP or another #MC will enter shutdown state */
gstatus &= ~MCG_STATUS_MCIP;
mca_wrmsr(MSR_IA32_MCG_STATUS, gstatus);
wmb();
/* If no valid errors and our stack is intact, we're done */
if (ripv && bs.errcnt == 0) {
vcpu_schedule_unlock_irq(v);
irqlocked = 0;
goto cmn_handler_done;
}
if (bs.uc || bs.pcc)
add_taint(TAINT_MACHINE_CHECK);
/* Machine check exceptions will usually be for UC and/or PCC errors,
* but it is possible to configure machine check for some classes
* of corrected error.
*
* UC errors could compromise any domain or the hypervisor
* itself - for example a cache writeback of modified data that
* turned out to be bad could be for data belonging to anyone, not
* just the current domain. In the absence of known data poisoning
* to prevent consumption of such bad data in the system we regard
* all UC errors as terminal. It may be possible to attempt some
* heuristics based on the address affected, which guests have
* mappings to that mfn etc.
*
* PCC errors apply to the current context.
*
* If MCG_STATUS indicates !RIPV then even a #MC that is not UC
* and not PCC is terminal - the return instruction pointer
* pushed onto the stack is bogus. If the interrupt context is
* the hypervisor or dom0 the game is over, otherwise we can
* limit the impact to a single domU but only if we trampoline
* somewhere safely - we can't return and unwind the stack.
* Since there is no trampoline in place we will treat !RIPV
* as terminal for any context.
*/
ctx_xen = SEG_PL(regs->cs) == 0;
ctx_dom0 = !ctx_xen && (domid == 0);
ctx_domU = !ctx_xen && !ctx_dom0;
xen_state_lost = bs.uc != 0 || (ctx_xen && (bs.pcc || !ripv)) ||
!ripv;
dom0_state_lost = bs.uc != 0 || (ctx_dom0 && (bs.pcc || !ripv));
domU_state_lost = bs.uc != 0 || (ctx_domU && (bs.pcc || !ripv));
if (xen_state_lost) {
/* Now we are going to panic anyway. Allow interrupts, so that
* printk on serial console can work. */
vcpu_schedule_unlock_irq(v);
irqlocked = 0;
printk("Terminal machine check exception occurred in "
"hypervisor context.\n");
/* If MCG_STATUS_EIPV indicates, the IP on the stack is related
* to the error then it makes sense to print a stack trace.
* That can be useful for more detailed error analysis and/or
* error case studies to figure out, if we can clear
* xen_impacted and kill a DomU instead
* (i.e. if a guest only control structure is affected, but then
* we must ensure the bad pages are not re-used again).
*/
if (bs.eipv & MCG_STATUS_EIPV) {
printk("MCE: Instruction Pointer is related to the "
"error, therefore print the execution state.\n");
show_execution_state(regs);
}
/* Commit the telemetry so that panic flow can find it. */
if (mctc != NULL) {
x86_mcinfo_dump(mci);
mctelem_commit(mctc);
}
mc_panic("Hypervisor state lost due to machine check "
"exception.\n");
/*NOTREACHED*/
}
/*
* Xen hypervisor state is intact. If dom0 state is lost then
* give it a chance to decide what to do if it has registered
* a handler for this event, otherwise panic.
*
* XXFM Could add some Solaris dom0 contract kill here?
*/
if (dom0_state_lost) {
if (dom0 && dom0->max_vcpus && dom0->vcpu[0] &&
guest_has_trap_callback(dom0, 0, TRAP_machine_check)) {
dom_state = DOM0_TRAP;
send_guest_trap(dom0, 0, TRAP_machine_check);
/* XXFM case of return with !ripv ??? */
} else {
/* Commit telemetry for panic flow. */
if (mctc != NULL) {
x86_mcinfo_dump(mci);
mctelem_commit(mctc);
}
mc_panic("Dom0 state lost due to machine check "
"exception\n");
/*NOTREACHED*/
}
}
/*
* If a domU has lost state then send it a trap if it has registered
* a handler, otherwise crash the domain.
* XXFM Revisit this functionality.
*/
if (domU_state_lost) {
if (guest_has_trap_callback(v->domain, v->vcpu_id,
TRAP_machine_check)) {
dom_state = DOMU_TRAP;
send_guest_trap(curdom, v->vcpu_id,
TRAP_machine_check);
} else {
dom_state = DOMU_KILLED;
/* Enable interrupts. This basically results in
* calling sti on the *physical* cpu. But after
* domain_crash() the vcpu pointer is invalid.
* Therefore, we must unlock the irqs before killing
* it. */
vcpu_schedule_unlock_irq(v);
irqlocked = 0;
/* DomU is impacted. Kill it and continue. */
domain_crash(curdom);
}
}
switch (dom_state) {
case DOM0_TRAP:
case DOMU_TRAP:
/* Enable interrupts. */
vcpu_schedule_unlock_irq(v);
irqlocked = 0;
/* guest softirqs and event callbacks are scheduled
* immediately after this handler exits. */
break;
case DOMU_KILLED:
/* Nothing to do here. */
break;
case DOM_NORMAL:
vcpu_schedule_unlock_irq(v);
irqlocked = 0;
break;
}
cmn_handler_done:
BUG_ON(irqlocked);
BUG_ON(!ripv);
if (bs.errcnt) {
/* Not panicing, so forward telemetry to dom0 now if it
* is interested. */
if (dom0_vmce_enabled()) {
if (mctc != NULL)
mctelem_commit(mctc);
send_guest_global_virq(dom0, VIRQ_MCA);
} else {
x86_mcinfo_dump(mci);
if (mctc != NULL)
mctelem_dismiss(mctc);
}
} else if (mctc != NULL) {
mctelem_dismiss(mctc);
}
}
/* Machine Check Handler for AMD K8 family series */
void k8_machine_check(struct cpu_user_regs *regs, long error_code)
{
struct vcpu *vcpu = current;
struct domain *curdom;
struct mc_info *mc_data;
struct mcinfo_global mc_global;
struct mcinfo_bank mc_info;
uint64_t status, addrv, miscv, uc;
uint32_t i;
unsigned int cpu_nr;
uint32_t xen_impacted = 0;
#define DOM_NORMAL 0
#define DOM0_TRAP 1
#define DOMU_TRAP 2
#define DOMU_KILLED 4
uint32_t dom_state = DOM_NORMAL;
/* This handler runs as interrupt gate. So IPIs from the
* polling service routine are defered until we finished.
*/
/* Disable interrupts for the _vcpu_. It may not re-scheduled to
* an other physical CPU or the impacted process in the guest
* continues running with corrupted data, otherwise. */
vcpu_schedule_lock_irq(vcpu);
mc_data = x86_mcinfo_getptr();
cpu_nr = smp_processor_id();
curdom = vcpu->domain;
memset(&mc_global, 0, sizeof(mc_global));
mc_global.common.type = MC_TYPE_GLOBAL;
mc_global.common.size = sizeof(mc_global);
mc_global.mc_domid = curdom->domain_id; /* impacted domain */
mc_global.mc_coreid = vcpu->processor; /* impacted physical cpu */
BUG_ON(cpu_nr != vcpu->processor);
mc_global.mc_core_threadid = 0;
mc_global.mc_vcpuid = vcpu->vcpu_id; /* impacted vcpu */
#if 0 /* TODO: on which socket is this physical core?
It's not clear to me how to figure this out. */
mc_global.mc_socketid = ???;
#endif
mc_global.mc_flags |= MC_FLAG_UNCORRECTABLE;
rdmsrl(MSR_IA32_MCG_STATUS, mc_global.mc_gstatus);
/* Quick check, who is impacted */
xen_impacted = is_idle_domain(curdom);
/* Dom0 */
x86_mcinfo_clear(mc_data);
x86_mcinfo_add(mc_data, &mc_global);
for (i = 0; i < nr_mce_banks; i++) {
struct domain *d;
rdmsrl(MSR_IA32_MC0_STATUS + 4 * i, status);
if (!(status & MCi_STATUS_VAL))
continue;
/* An error happened in this bank.
* This is expected to be an uncorrectable error,
* since correctable errors get polled.
*/
uc = status & MCi_STATUS_UC;
memset(&mc_info, 0, sizeof(mc_info));
mc_info.common.type = MC_TYPE_BANK;
mc_info.common.size = sizeof(mc_info);
mc_info.mc_bank = i;
mc_info.mc_status = status;
addrv = 0;
if (status & MCi_STATUS_ADDRV) {
rdmsrl(MSR_IA32_MC0_ADDR + 4 * i, addrv);
d = maddr_get_owner(addrv);
if (d != NULL)
mc_info.mc_domid = d->domain_id;
}
miscv = 0;
if (status & MCi_STATUS_MISCV)
rdmsrl(MSR_IA32_MC0_MISC + 4 * i, miscv);
mc_info.mc_addr = addrv;
mc_info.mc_misc = miscv;
x86_mcinfo_add(mc_data, &mc_info); /* Dom0 */
if (mc_callback_bank_extended)
mc_callback_bank_extended(mc_data, i, status);
/* clear status */
wrmsrl(MSR_IA32_MC0_STATUS + 4 * i, 0x0ULL);
wmb();
add_taint(TAINT_MACHINE_CHECK);
}
status = mc_global.mc_gstatus;
/* clear MCIP or cpu enters shutdown state
* in case another MCE occurs. */
status &= ~MCG_STATUS_MCIP;
wrmsrl(MSR_IA32_MCG_STATUS, status);
wmb();
/* For the details see the discussion "MCE/MCA concept" on xen-devel.
* The thread started here:
* http://lists.xensource.com/archives/html/xen-devel/2007-05/msg01015.html
*/
/* MCG_STATUS_RIPV:
* When this bit is not set, then the instruction pointer onto the stack
* to resume at is not valid. If xen is interrupted, then we panic anyway
* right below. Otherwise it is up to the guest to figure out if
* guest kernel or guest userland is affected and should kill either
* itself or the affected process.
*/
/* MCG_STATUS_EIPV:
* Evaluation of EIPV is the job of the guest.
*/
if (xen_impacted) {
/* Now we are going to panic anyway. Allow interrupts, so that
* printk on serial console can work. */
vcpu_schedule_unlock_irq(vcpu);
/* Uh, that means, machine check exception
* inside Xen occured. */
printk("Machine check exception occured in Xen.\n");
/* if MCG_STATUS_EIPV indicates, the IP on the stack is related
* to the error then it makes sense to print a stack trace.
* That can be useful for more detailed error analysis and/or
* error case studies to figure out, if we can clear
* xen_impacted and kill a DomU instead
* (i.e. if a guest only control structure is affected, but then
* we must ensure the bad pages are not re-used again).
*/
if (status & MCG_STATUS_EIPV) {
printk("MCE: Instruction Pointer is related to the error. "
"Therefore, print the execution state.\n");
show_execution_state(regs);
}
x86_mcinfo_dump(mc_data);
mc_panic("End of MCE. Use mcelog to decode above error codes.\n");
}
/* If Dom0 registered a machine check handler, which is only possible
* with a PV MCA driver, then ... */
if ( guest_has_trap_callback(dom0, 0, TRAP_machine_check) ) {
dom_state = DOM0_TRAP;
/* ... deliver machine check trap to Dom0. */
send_guest_trap(dom0, 0, TRAP_machine_check);
/* Xen may tell Dom0 now to notify the DomU.
* But this will happen through a hypercall. */
} else
/* Dom0 did not register a machine check handler, but if DomU
* did so, then... */
if ( guest_has_trap_callback(curdom, vcpu->vcpu_id, TRAP_machine_check) ) {
dom_state = DOMU_TRAP;
/* ... deliver machine check trap to DomU */
send_guest_trap(curdom, vcpu->vcpu_id, TRAP_machine_check);
} else {
/* hmm... noone feels responsible to handle the error.
* So, do a quick check if a DomU is impacted or not.
*/
if (curdom == dom0) {
/* Dom0 is impacted. Since noone can't handle
* this error, panic! */
x86_mcinfo_dump(mc_data);
mc_panic("MCE occured in Dom0, which it can't handle\n");
/* UNREACHED */
} else {
dom_state = DOMU_KILLED;
/* Enable interrupts. This basically results in
* calling sti on the *physical* cpu. But after
* domain_crash() the vcpu pointer is invalid.
* Therefore, we must unlock the irqs before killing
* it. */
vcpu_schedule_unlock_irq(vcpu);
/* DomU is impacted. Kill it and continue. */
domain_crash(curdom);
}
}
switch (dom_state) {
case DOM0_TRAP:
case DOMU_TRAP:
/* Enable interrupts. */
vcpu_schedule_unlock_irq(vcpu);
/* guest softirqs and event callbacks are scheduled
* immediately after this handler exits. */
break;
case DOMU_KILLED:
/* Nothing to do here. */
break;
default:
BUG();
}
}