KVM: x86: Plumb the emulator's starting RIP into nested intercept checks

When checking for intercept when emulating an instruction on behalf of L2,
pass the emulator's view of the RIP of the instruction being emulated to
vendor code.  Unlike SVM, which communicates the next RIP on VM-Exit,
VMX communicates the length of the instruction that generated the VM-Exit,
i.e. requires the current and next RIPs.

Note, unless userspace modifies RIP during a userspace exit that requires
completion, kvm_rip_read() will contain the same information.  Pass the
emulator's view largely out of a paranoia, and because there is no
meaningful cost in doing so.

Link: https://lore.kernel.org/r/20250201015518.689704-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/emulate.c

@@ -480,6 +480,7 @@ static int emulator_check_intercept(struct x86_emulate_ctxt *ctxt,
 		.src_type   = ctxt->src.type,
 		.dst_type   = ctxt->dst.type,
 		.ad_bytes   = ctxt->ad_bytes,
+		.rip	    = ctxt->eip,
 		.next_rip   = ctxt->_eip,
 	};
 

arch/x86/kvm/kvm_emulate.h

@@ -47,6 +47,7 @@ struct x86_instruction_info {
 	u8  src_type;		/* type of source operand		*/
 	u8  dst_type;		/* type of destination operand		*/
 	u8  ad_bytes;           /* size of src/dst address              */
+	u64 rip;		/* rip of the instruction		*/
 	u64 next_rip;           /* rip following the instruction        */
 };