#define PPC_INST_MFSPR_PVR 0x7c1f42a6
#define PPC_INST_MFSPR_PVR_MASK 0xfc1ffffe
#define PPC_INST_MTMSRD 0x7c000164
+#define PPC_INST_PASTE 0x7c20070d
+#define PPC_INST_PASTE_MASK 0xfc2007ff
#define PPC_INST_POPCNTB 0x7c0000f4
#define PPC_INST_POPCNTB_MASK 0xfc0007fe
#define PPC_INST_RFEBB 0x4c000124
}
/*
+ * If the executed instruction that caused the fault was a paste, then
+ * clear regs CR0[EQ], advance NIP, and return 0. Else return error code.
+ */
+static int do_fail_paste(void)
+{
+ struct pt_regs *regs = current->thread.regs;
+ u32 instword;
+
+ if (WARN_ON_ONCE(!regs))
+ return -EINVAL;
+
+ if (WARN_ON_ONCE(!user_mode(regs)))
+ return -EINVAL;
+
+ /*
+ * If we couldn't translate the instruction, the driver should
+ * return success without handling the fault, it will be retried
+ * or the instruction fetch will fault.
+ */
+ if (get_user(instword, (u32 __user *)(regs->nip)))
+ return -EAGAIN;
+
+ /*
+ * Not a paste instruction, driver may fail the fault.
+ */
+ if ((instword & PPC_INST_PASTE_MASK) != PPC_INST_PASTE)
+ return -ENOENT;
+
+ regs->ccr &= ~0xe0000000; /* Clear CR0[0-2] to fail paste */
+ regs_add_return_ip(regs, 4); /* Emulate the paste */
+
+ return 0;
+}
+
+/*
* This fault handler is invoked when the core generates page fault on
* the paste address. Happens if the kernel closes window in hypervisor
* (on pseries) due to lost credit or the paste address is not mapped.
struct vas_window *txwin;
vm_fault_t fault;
u64 paste_addr;
+ int ret;
/*
* window is not opened. Shouldn't expect this error.
}
mutex_unlock(&txwin->task_ref.mmap_mutex);
+ /*
+ * Received this fault due to closing the actual window.
+ * It can happen during migration or lost credits.
+ * Since no mapping, return the paste instruction failure
+ * to the user space.
+ */
+ ret = do_fail_paste();
+ /*
+ * The user space can retry several times until success (needed
+ * for migration) or should fallback to SW compression or
+ * manage with the existing open windows if available.
+ * Looking at sysfs interface, it can determine whether these
+ * failures are coming during migration or core removal:
+ * nr_used_credits > nr_total_credits when lost credits
+ */
+ if (!ret || (ret == -EAGAIN))
+ return VM_FAULT_NOPAGE;
+
return VM_FAULT_SIGBUS;
}