[RFC PATCH v6 25/92] kvm: x86: intercept the write access on sidt and other emulated instructions

[Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>]

This is needed for the introspection subsystem to track the changes to
descriptor table registers.

CC: Joerg Roedel <joro@xxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7aef002be551..c28e2a20dec2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5185,11 +5185,14 @@ static int kvm_write_guest_virt_helper(gva_t addr, void *val, unsigned int bytes
 
 		if (gpa == UNMAPPED_GVA)
 			return X86EMUL_PROPAGATE_FAULT;
+		if (!kvm_page_track_prewrite(vcpu, gpa, addr, data, towrite))
+			return X86EMUL_RETRY_INSTR;
 		ret = kvm_vcpu_write_guest(vcpu, gpa, data, towrite);
 		if (ret < 0) {
 			r = X86EMUL_IO_NEEDED;
 			goto out;
 		}
+		kvm_page_track_write(vcpu, gpa, addr, data, towrite);
 
 		bytes -= towrite;
 		data += towrite;