[PATCH 2/2] kvm: allow qemu to set EPT identity mapping address

[Sheng Yang <sheng@xxxxxxxxxxxxxxx>]

If we use larger BIOS image than current 256KB, we would need move reserved
TSS and EPT identity mapping pages. Currently TSS support this, but not
EPT.

Signed-off-by: Sheng Yang <sheng@xxxxxxxxxxxxxxx>
---
 kvm/include/linux/kvm.h |    2 ++
 qemu-kvm-x86.c          |   45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/kvm/include/linux/kvm.h b/kvm/include/linux/kvm.h
index 790601d..9161595 100644
--- a/kvm/include/linux/kvm.h
+++ b/kvm/include/linux/kvm.h
@@ -465,6 +465,7 @@ struct kvm_trace_rec {
 #define KVM_CAP_JOIN_MEMORY_REGIONS_WORKS 30
 #define KVM_CAP_PIT2 33
 #define KVM_CAP_PIT_STATE2 35
+#define KVM_CAP_SET_IDENTITY_MAP_ADDR 37
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -513,6 +514,7 @@ struct kvm_irq_routing {
 #define KVM_SET_USER_MEMORY_REGION _IOW(KVMIO, 0x46,\
 					struct kvm_userspace_memory_region)
 #define KVM_SET_TSS_ADDR          _IO(KVMIO, 0x47)
+#define KVM_SET_IDENTITY_MAP_ADDR _IO(KVMIO, 0x48)
 /*
  * KVM_CREATE_VCPU receives as a parameter the vcpu slot, and returns
  * a vcpu fd.
diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index daf60b6..8ec4e4c 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -74,6 +74,47 @@ static int kvm_init_tss(kvm_context_t kvm)
 	return 0;
 }
 
+static int kvm_set_identity_map_addr(kvm_context_t kvm, unsigned long addr)
+{
+#ifdef KVM_CAP_SET_IDENTITY_MAP_ADDR
+	int r;
+
+	r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_SET_IDENTITY_MAP_ADDR);
+	if (r > 0) {
+		r = ioctl(kvm->vm_fd, KVM_SET_IDENTITY_MAP_ADDR, addr);
+		if (r == -1) {
+			fprintf(stderr, "kvm_set_identity_map_addr: %m\n");
+			return -errno;
+		}
+		return 0;
+	}
+#endif
+	return -ENOSYS;
+}
+
+static int kvm_init_identity_map_page(kvm_context_t kvm)
+{
+#ifdef KVM_CAP_SET_IDENTITY_MAP_ADDR
+	int r;
+
+	r = ioctl(kvm->fd, KVM_CHECK_EXTENSION, KVM_CAP_SET_IDENTITY_MAP_ADDR);
+	if (r > 0) {
+		/*
+		 * this address is 4 pages before the bios, and the bios should present
+		 * as unavaible memory
+		 */
+		r = kvm_set_identity_map_addr(kvm, 0xfffbc000);
+		if (r < 0) {
+			fprintf(stderr, "kvm_init_identity_map_page: "
+				"unable to set identity mapping addr\n");
+			return r;
+		}
+
+	}
+#endif
+	return 0;
+}
+
 static int kvm_create_pit(kvm_context_t kvm)
 {
 #ifdef KVM_CAP_PIT
@@ -105,6 +146,10 @@ int kvm_arch_create(kvm_context_t kvm, unsigned long phys_mem_bytes,
 	if (r < 0)
 		return r;
 
+	r = kvm_init_identity_map_page(kvm);
+	if (r < 0)
+		return r;
+
 	r = kvm_create_pit(kvm);
 	if (r < 0)
 		return r;
-- 
1.5.4.5

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