KVM: x86: ignore access permissions for hypercall patching

[Marcelo Tosatti <mtosatti@redhat.com>]

Ignore access permissions while patching hypercall instructions. 
Otherwise KVM injects a page fault when trying to patch vmcall 
on read-only text regions:

Freeing initrd memory: 8843k freed
Freeing unused kernel memory: 660k freed
Write protecting the kernel text: 4780k
Write protecting the kernel read-only data: 1912k
BUG: unable to handle kernel paging request at c01292e3
IP: [<c01292e3>] kvm_leave_lazy_mmu+0x43/0x70
*pde = 00910067 *pte = 00129161
Oops: 0003 [#1] SMP

CC: stable@kernel.org
Reported-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 703f637..bf5c83f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3253,12 +3253,17 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
 static int emulator_write_emulated_onepage(unsigned long addr,
 					   const void *val,
 					   unsigned int bytes,
-					   struct kvm_vcpu *vcpu)
+					   struct kvm_vcpu *vcpu,
+					   bool guest_initiated)
 {
 	gpa_t                 gpa;
 	u32 error_code;
 
-	gpa = kvm_mmu_gva_to_gpa_write(vcpu, addr, &error_code);
+
+	if (guest_initiated)
+		gpa = kvm_mmu_gva_to_gpa_write(vcpu, addr, &error_code);
+	else
+		gpa = kvm_mmu_gva_to_gpa_system(vcpu, addr, &error_code);
 
 	if (gpa == UNMAPPED_GVA) {
 		kvm_inject_page_fault(vcpu, addr, error_code);
@@ -3289,24 +3294,35 @@ mmio:
 	return X86EMUL_CONTINUE;
 }
 
-int emulator_write_emulated(unsigned long addr,
+int __emulator_write_emulated(unsigned long addr,
 				   const void *val,
 				   unsigned int bytes,
-				   struct kvm_vcpu *vcpu)
+				   struct kvm_vcpu *vcpu,
+				   bool guest_initiated)
 {
 	/* Crossing a page boundary? */
 	if (((addr + bytes - 1) ^ addr) & PAGE_MASK) {
 		int rc, now;
 
 		now = -addr & ~PAGE_MASK;
-		rc = emulator_write_emulated_onepage(addr, val, now, vcpu);
+		rc = emulator_write_emulated_onepage(addr, val, now, vcpu,
+						     guest_initiated);
 		if (rc != X86EMUL_CONTINUE)
 			return rc;
 		addr += now;
 		val += now;
 		bytes -= now;
 	}
-	return emulator_write_emulated_onepage(addr, val, bytes, vcpu);
+	return emulator_write_emulated_onepage(addr, val, bytes, vcpu,
+					       guest_initiated);
+}
+
+int emulator_write_emulated(unsigned long addr,
+				   const void *val,
+				   unsigned int bytes,
+				   struct kvm_vcpu *vcpu)
+{
+	return __emulator_write_emulated(addr, val, bytes, vcpu, true);
 }
 EXPORT_SYMBOL_GPL(emulator_write_emulated);
 
@@ -3997,7 +4013,7 @@ int kvm_fix_hypercall(struct kvm_vcpu *vcpu)
 
 	kvm_x86_ops->patch_hypercall(vcpu, instruction);
 
-	return emulator_write_emulated(rip, instruction, 3, vcpu);
+	return __emulator_write_emulated(rip, instruction, 3, vcpu, false);
 }
 
 static u64 mk_cr_64(u64 curr_cr, u32 new_val)