vmm(4): set RAX guest register state based on VMCB

The read/write register routines for SVM didn't acknowledge RAX in
the VMCB as the de facto RAX state. When writing gprs, vmm should
update RAX in the VMCB. When reading, it should be setting the guest
regs state based on the VMCB.

Needed for proper mmio emulation in userland.

ok mlarkin@

diff --git a/sys/arch/amd64/amd64/vmm.c b/sys/arch/amd64/amd64/vmm.c
index d17038f..f6ad02e 100644 (file)
--- a/sys/arch/amd64/amd64/vmm.c
+++ b/sys/arch/amd64/amd64/vmm.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vmm.c,v 1.325 2022/11/06 19:00:37 dv Exp $    */
+/*     $OpenBSD: vmm.c,v 1.326 2022/11/07 12:29:12 dv Exp $    */
 /*
  * Copyright (c) 2014 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -2233,7 +2233,7 @@ vcpu_readregs_svm(struct vcpu *vcpu, uint64_t regmask,
        struct vmcb *vmcb = (struct vmcb *)vcpu->vc_control_va;
 
        if (regmask & VM_RWREGS_GPRS) {
-               gprs[VCPU_REGS_RAX] = vcpu->vc_gueststate.vg_rax;
+               gprs[VCPU_REGS_RAX] = vmcb->v_rax;
                gprs[VCPU_REGS_RBX] = vcpu->vc_gueststate.vg_rbx;
                gprs[VCPU_REGS_RCX] = vcpu->vc_gueststate.vg_rcx;
                gprs[VCPU_REGS_RDX] = vcpu->vc_gueststate.vg_rdx;
@@ -2536,6 +2536,7 @@ vcpu_writeregs_svm(struct vcpu *vcpu, uint64_t regmask,
                vcpu->vc_gueststate.vg_rbp = gprs[VCPU_REGS_RBP];
                vcpu->vc_gueststate.vg_rip = gprs[VCPU_REGS_RIP];
 
+               vmcb->v_rax = gprs[VCPU_REGS_RAX];
                vmcb->v_rip = gprs[VCPU_REGS_RIP];
                vmcb->v_rsp = gprs[VCPU_REGS_RSP];
                vmcb->v_rflags = gprs[VCPU_REGS_RFLAGS];