[PATCH v4 12/17] KVM: PPC: Book3S HV: XIVE: add a TIMA mapping

[Cédric Le Goater]

Each thread has an associated Thread Interrupt Management context
composed of a set of registers. These registers let the thread handle
priority management and interrupt acknowledgment. The most important
are :

    - Interrupt Pending Buffer     (IPB)
    - Current Processor Priority   (CPPR)
    - Notification Source Register (NSR)

They are exposed to software in four different pages each proposing a
view with a different privilege. The first page is for the physical
thread context and the second for the hypervisor. Only the third
(operating system) and the fourth (user level) are exposed the guest.

A custom VM fault handler will populate the VMA with the appropriate
pages, which should only be the OS page for now.

Signed-off-by: Cédric Le Goater <clg at kaod.org>
Reviewed-by: David Gibson <david at gibson.dropbear.id.au>
---
 arch/powerpc/include/asm/xive.h            |  1 +
 arch/powerpc/include/uapi/asm/kvm.h        |  2 ++
 arch/powerpc/kvm/book3s_xive_native.c      | 39 ++++++++++++++++++++++
 arch/powerpc/sysdev/xive/native.c          | 11 ++++++
 Documentation/virtual/kvm/devices/xive.txt | 23 +++++++++++++
 5 files changed, 76 insertions(+)

diff --git a/arch/powerpc/include/asm/xive.h b/arch/powerpc/include/asm/xive.h
index c4e88abd3b67..eaf76f57023a 100644
--- a/arch/powerpc/include/asm/xive.h
+++ b/arch/powerpc/include/asm/xive.h
@@ -23,6 +23,7 @@
  * same offset regardless of where the code is executing
  */
 extern void __iomem *xive_tima;
+extern unsigned long xive_tima_os;
 
 /*
  * Offset in the TM area of our current execution level (provided by
diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
index cd3f16b70a2e..0998e8edc91a 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -720,4 +720,6 @@ struct kvm_ppc_xive_eq {
 
 #define KVM_XIVE_EQ_ALWAYS_NOTIFY	0x00000001
 
+#define KVM_XIVE_TIMA_PAGE_OFFSET	0
+
 #endif /* __LINUX_KVM_POWERPC_H */
diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
index a8c62e07ebee..0cfad45d8b75 100644
--- a/arch/powerpc/kvm/book3s_xive_native.c
+++ b/arch/powerpc/kvm/book3s_xive_native.c
@@ -165,6 +165,44 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev,
 	return rc;
 }
 
+static vm_fault_t xive_native_tima_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+
+	switch (vmf->pgoff - vma->vm_pgoff) {
+	case 0: /* HW - forbid access */
+	case 1: /* HV - forbid access */
+		return VM_FAULT_SIGBUS;
+	case 2: /* OS */
+		vmf_insert_pfn(vma, vmf->address, xive_tima_os >> PAGE_SHIFT);
+		return VM_FAULT_NOPAGE;
+	case 3: /* USER - TODO */
+	default:
+		return VM_FAULT_SIGBUS;
+	}
+}
+
+static const struct vm_operations_struct xive_native_tima_vmops = {
+	.fault = xive_native_tima_fault,
+};
+
+static int kvmppc_xive_native_mmap(struct kvm_device *dev,
+				   struct vm_area_struct *vma)
+{
+	/* We only allow mappings at fixed offset for now */
+	if (vma->vm_pgoff == KVM_XIVE_TIMA_PAGE_OFFSET) {
+		if (vma_pages(vma) > 4)
+			return -EINVAL;
+		vma->vm_ops = &xive_native_tima_vmops;
+	} else {
+		return -EINVAL;
+	}
+
+	vma->vm_flags |= VM_IO | VM_PFNMAP;
+	vma->vm_page_prot = pgprot_noncached_wc(vma->vm_page_prot);
+	return 0;
+}
+
 static int kvmppc_xive_native_set_source(struct kvmppc_xive *xive, long irq,
 					 u64 addr)
 {
@@ -1043,6 +1081,7 @@ struct kvm_device_ops kvm_xive_native_ops = {
 	.set_attr = kvmppc_xive_native_set_attr,
 	.get_attr = kvmppc_xive_native_get_attr,
 	.has_attr = kvmppc_xive_native_has_attr,
+	.mmap = kvmppc_xive_native_mmap,
 };
 
 void kvmppc_xive_native_init_module(void)
diff --git a/arch/powerpc/sysdev/xive/native.c b/arch/powerpc/sysdev/xive/native.c
index 0c037e933e55..7782201e5fe8 100644
--- a/arch/powerpc/sysdev/xive/native.c
+++ b/arch/powerpc/sysdev/xive/native.c
@@ -521,6 +521,9 @@ u32 xive_native_default_eq_shift(void)
 }
 EXPORT_SYMBOL_GPL(xive_native_default_eq_shift);
 
+unsigned long xive_tima_os;
+EXPORT_SYMBOL_GPL(xive_tima_os);
+
 bool __init xive_native_init(void)
 {
 	struct device_node *np;
@@ -573,6 +576,14 @@ bool __init xive_native_init(void)
 	for_each_possible_cpu(cpu)
 		kvmppc_set_xive_tima(cpu, r.start, tima);
 
+	/* Resource 2 is OS window */
+	if (of_address_to_resource(np, 2, &r)) {
+		pr_err("Failed to get thread mgmnt area resource\n");
+		return false;
+	}
+
+	xive_tima_os = r.start;
+
 	/* Grab size of provisionning pages */
 	xive_parse_provisioning(np);
 
diff --git a/Documentation/virtual/kvm/devices/xive.txt b/Documentation/virtual/kvm/devices/xive.txt
index 702836d5ad7a..944fd0971b13 100644
--- a/Documentation/virtual/kvm/devices/xive.txt
+++ b/Documentation/virtual/kvm/devices/xive.txt
@@ -13,6 +13,29 @@ requires a POWER9 host and the guest OS should have support for the
 XIVE native exploitation interrupt mode. If not, it should run using
 the legacy interrupt mode, referred as XICS (POWER7/8).
 
+* Device Mappings
+
+  The KVM device exposes different MMIO ranges of the XIVE HW which
+  are required for interrupt management. These are exposed to the
+  guest in VMAs populated with a custom VM fault handler.
+
+  1. Thread Interrupt Management Area (TIMA)
+
+  Each thread has an associated Thread Interrupt Management context
+  composed of a set of registers. These registers let the thread
+  handle priority management and interrupt acknowledgment. The most
+  important are :
+
+      - Interrupt Pending Buffer     (IPB)
+      - Current Processor Priority   (CPPR)
+      - Notification Source Register (NSR)
+
+  They are exposed to software in four different pages each proposing
+  a view with a different privilege. The first page is for the
+  physical thread context and the second for the hypervisor. Only the
+  third (operating system) and the fourth (user level) are exposed the
+  guest.
+
 * Groups:
 
   1. KVM_DEV_XIVE_GRP_CTRL
-- 
2.20.1