5 files changed, 36 insertions, 2 deletions

diff --git a/Documentation/virtual/kvm/ppc-pv.txt b/Documentation/virtual/kvm/ppc-pv.txt
index 4643cde517c4..319560646f32 100644
--- a/Documentation/virtual/kvm/ppc-pv.txt
+++ b/Documentation/virtual/kvm/ppc-pv.txt
@@ -94,10 +94,24 @@ a bitmap of available features inside the magic page.
 The following enhancements to the magic page are currently available:
 
   KVM_MAGIC_FEAT_SR             Maps SR registers r/w in the magic page
+  KVM_MAGIC_FEAT_MAS0_TO_SPRG7  Maps MASn, ESR, PIR and high SPRGs
 
 For enhanced features in the magic page, please check for the existence of the
 feature before using them!
 
+Magic page flags
+================
+
+In addition to features that indicate whether a host is capable of a particular
+feature we also have a channel for a guest to tell the guest whether it's capable
+of something. This is what we call "flags".
+
+Flags are passed to the host in the low 12 bits of the Effective Address.
+
+The following flags are currently available for a guest to expose:
+
+  MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correclty wrt magic page
+
 MSR bits
 ========
 
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 29fbb554af5c..bb66d8b8efdf 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -631,6 +631,7 @@ struct kvm_vcpu_arch {
 #endif
         unsigned long magic_page_pa; /* phys addr to map the magic page to */
         unsigned long magic_page_ea; /* effect. addr to map the magic page to */
+        bool disable_kernel_nx;
 
         int irq_type;           /* one of KVM_IRQ_* */
         int irq_cpu_id;
diff --git a/arch/powerpc/include/uapi/asm/kvm_para.h b/arch/powerpc/include/uapi/asm/kvm_para.h
index e3af3286a068..91e42f09b323 100644
--- a/arch/powerpc/include/uapi/asm/kvm_para.h
+++ b/arch/powerpc/include/uapi/asm/kvm_para.h
@@ -82,10 +82,16 @@ struct kvm_vcpu_arch_shared {
 
 #define KVM_FEATURE_MAGIC_PAGE  1
 
+/* Magic page flags from host to guest */
+
 #define KVM_MAGIC_FEAT_SR               (1 << 0)
 
 /* MASn, ESR, PIR, and high SPRGs */
 #define KVM_MAGIC_FEAT_MAS0_TO_SPRG7    (1 << 1)
 
+/* Magic page flags from guest to host */
+
+#define MAGIC_PAGE_FLAG_NOT_MAPPED_NX   (1 << 0)
+
 
 #endif /* _UAPI__POWERPC_KVM_PARA_H__ */
diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c
index 278729f4df80..774a253ca4e1 100644
--- a/arch/powerpc/kvm/book3s_64_mmu.c
+++ b/arch/powerpc/kvm/book3s_64_mmu.c
@@ -313,6 +313,9 @@ do_second:
         gpte->raddr = (r & HPTE_R_RPN & ~eaddr_mask) | (eaddr & eaddr_mask);
         gpte->page_size = pgsize;
         gpte->may_execute = ((r & HPTE_R_N) ? false : true);
+        if (unlikely(vcpu->arch.disable_kernel_nx) &&
+            !(kvmppc_get_msr(vcpu) & MSR_PR))
+                gpte->may_execute = true;
         gpte->may_read = false;
         gpte->may_write = false;
 
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index b4e15bf3ff88..154f352c39ae 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -177,8 +177,18 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
                 vcpu->arch.shared_big_endian = shared_big_endian;
 #endif
 
-                vcpu->arch.magic_page_pa = param1;
-                vcpu->arch.magic_page_ea = param2;
+                if (!(param2 & MAGIC_PAGE_FLAG_NOT_MAPPED_NX)) {
+                        /*
+                         * Older versions of the Linux magic page code had
+                         * a bug where they would map their trampoline code
+                         * NX. If that's the case, remove !PR NX capability.
+                         */
+                        vcpu->arch.disable_kernel_nx = true;
+                        kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
+                }
+
+                vcpu->arch.magic_page_pa = param1 & ~0xfffULL;
+                vcpu->arch.magic_page_ea = param2 & ~0xfffULL;
 
                 r2 = KVM_MAGIC_FEAT_SR | KVM_MAGIC_FEAT_MAS0_TO_SPRG7;