[src/trunk]: src/sys/dev/nvmm/x86 nvmm-x86-vmx: improve the handling of CR0

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/fea638f40125
branches:  trunk
changeset: 954696:fea638f40125
user:      maxv <maxv%NetBSD.org@localhost>
date:      Tue Sep 08 17:00:07 2020 +0000

description:
nvmm-x86-vmx: improve the handling of CR0

 - CR0_ET is hard-wired to 1 in the cpu, so force CR0_ET to 1 in the
   shadow.
 - Clarify.

diffstat:

 sys/dev/nvmm/x86/nvmm_x86_vmx.c |  68 ++++++++++++++++++++++++++--------------
 1 files changed, 44 insertions(+), 24 deletions(-)

diffs (149 lines):

diff -r 1b69c0bb1f32 -r fea638f40125 sys/dev/nvmm/x86/nvmm_x86_vmx.c
--- a/sys/dev/nvmm/x86/nvmm_x86_vmx.c   Tue Sep 08 16:58:38 2020 +0000
+++ b/sys/dev/nvmm/x86/nvmm_x86_vmx.c   Tue Sep 08 17:00:07 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: nvmm_x86_vmx.c,v 1.78 2020/09/06 02:18:53 riastradh Exp $      */
+/*     $NetBSD: nvmm_x86_vmx.c,v 1.79 2020/09/08 17:00:07 maxv Exp $   */
 
 /*
  * Copyright (c) 2018-2020 Maxime Villard, m00nbsd.net
@@ -29,7 +29,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: nvmm_x86_vmx.c,v 1.78 2020/09/06 02:18:53 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: nvmm_x86_vmx.c,v 1.79 2020/09/08 17:00:07 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -728,8 +728,8 @@
 #define MSRBM_NPAGES   1
 #define MSRBM_SIZE     (MSRBM_NPAGES * PAGE_SIZE)
 
-#define CR0_STATIC \
-       (CR0_NW|CR0_CD|CR0_ET)
+#define CR0_STATIC_MASK \
+       (CR0_ET | CR0_NW | CR0_CD)
 
 #define CR4_VALID \
        (CR4_VME |                      \
@@ -1572,7 +1572,7 @@
     uint64_t qual)
 {
        struct vmx_cpudata *cpudata = vcpu->cpudata;
-       uint64_t type, gpr, oldcr0, cr0;
+       uint64_t type, gpr, oldcr0, realcr0, fakecr0;
        uint64_t efer, ctls1;
 
        type = __SHIFTOUT(qual, VMX_QUAL_CR_TYPE);
@@ -1584,15 +1584,24 @@
        KASSERT(gpr < 16);
 
        if (gpr == NVMM_X64_GPR_RSP) {
-               gpr = vmx_vmread(VMCS_GUEST_RSP);
+               fakecr0 = vmx_vmread(VMCS_GUEST_RSP);
        } else {
-               gpr = cpudata->gprs[gpr];
+               fakecr0 = cpudata->gprs[gpr];
        }
 
-       cr0 = gpr | CR0_NE | CR0_ET;
-       cr0 &= ~(CR0_NW|CR0_CD);
-
-       if (vmx_check_cr(cr0, vmx_cr0_fixed0, vmx_cr0_fixed1) == -1) {
+       /*
+        * fakecr0 is the value the guest believes is in %cr0. realcr0 is the
+        * actual value in %cr0.
+        *
+        * In fakecr0 we must force CR0_ET to 1.
+        *
+        * In realcr0 we must force CR0_NW and CR0_CD to 0, and CR0_ET and
+        * CR0_NE to 1.
+        */
+       fakecr0 |= CR0_ET;
+       realcr0 = (fakecr0 & ~CR0_STATIC_MASK) | CR0_ET | CR0_NE;
+
+       if (vmx_check_cr(realcr0, vmx_cr0_fixed0, vmx_cr0_fixed1) == -1) {
                return -1;
        }
 
@@ -1601,7 +1610,7 @@
         * from CR3.
         */
 
-       if (cr0 & CR0_PG) {
+       if (realcr0 & CR0_PG) {
                ctls1 = vmx_vmread(VMCS_ENTRY_CTLS);
                efer = vmx_vmread(VMCS_GUEST_IA32_EFER);
                if (efer & EFER_LME) {
@@ -1615,14 +1624,14 @@
                vmx_vmwrite(VMCS_ENTRY_CTLS, ctls1);
        }
 
-       oldcr0 = (vmx_vmread(VMCS_CR0_SHADOW) & CR0_STATIC) |
-           (vmx_vmread(VMCS_GUEST_CR0) & ~CR0_STATIC);
-       if ((oldcr0 ^ gpr) & CR0_TLB_FLUSH) {
+       oldcr0 = (vmx_vmread(VMCS_CR0_SHADOW) & CR0_STATIC_MASK) |
+           (vmx_vmread(VMCS_GUEST_CR0) & ~CR0_STATIC_MASK);
+       if ((oldcr0 ^ fakecr0) & CR0_TLB_FLUSH) {
                cpudata->gtlb_want_flush = true;
        }
 
-       vmx_vmwrite(VMCS_CR0_SHADOW, gpr);
-       vmx_vmwrite(VMCS_GUEST_CR0, cr0);
+       vmx_vmwrite(VMCS_CR0_SHADOW, fakecr0);
+       vmx_vmwrite(VMCS_GUEST_CR0, realcr0);
        vmx_inkernel_advance();
        return 0;
 }
@@ -2574,15 +2583,26 @@
 
        if (flags & NVMM_X64_STATE_CRS) {
                /*
-                * CR0_NE and CR4_VMXE are mandatory.
+                * CR0_ET must be 1 both in the shadow and the real register.
+                * CR0_NE must be 1 in the real register.
+                * CR0_NW and CR0_CD must be 0 in the real register.
                 */
-               vmx_vmwrite(VMCS_CR0_SHADOW, state->crs[NVMM_X64_CR_CR0]);
+               vmx_vmwrite(VMCS_CR0_SHADOW,
+                   (state->crs[NVMM_X64_CR_CR0] & CR0_STATIC_MASK) |
+                   CR0_ET);
                vmx_vmwrite(VMCS_GUEST_CR0,
-                   state->crs[NVMM_X64_CR_CR0] | CR0_NE);
+                   (state->crs[NVMM_X64_CR_CR0] & ~CR0_STATIC_MASK) |
+                   CR0_ET | CR0_NE);
+
                cpudata->gcr2 = state->crs[NVMM_X64_CR_CR2];
-               vmx_vmwrite(VMCS_GUEST_CR3, state->crs[NVMM_X64_CR_CR3]); // XXX PDPTE?
+
+               /* XXX We are not handling PDPTE here. */
+               vmx_vmwrite(VMCS_GUEST_CR3, state->crs[NVMM_X64_CR_CR3]);
+
+               /* CR4_VMXE is mandatory. */
                vmx_vmwrite(VMCS_GUEST_CR4,
                    (state->crs[NVMM_X64_CR_CR4] & CR4_VALID) | CR4_VMXE);
+
                cpudata->gcr8 = state->crs[NVMM_X64_CR_CR8];
 
                if (vmx_xcr0_mask != 0) {
@@ -2715,8 +2735,8 @@
 
        if (flags & NVMM_X64_STATE_CRS) {
                state->crs[NVMM_X64_CR_CR0] =
-                   (vmx_vmread(VMCS_CR0_SHADOW) & CR0_STATIC) |
-                   (vmx_vmread(VMCS_GUEST_CR0) & ~CR0_STATIC);
+                   (vmx_vmread(VMCS_CR0_SHADOW) & CR0_STATIC_MASK) |
+                   (vmx_vmread(VMCS_GUEST_CR0) & ~CR0_STATIC_MASK);
                state->crs[NVMM_X64_CR_CR2] = cpudata->gcr2;
                state->crs[NVMM_X64_CR_CR3] = vmx_vmread(VMCS_GUEST_CR3);
                state->crs[NVMM_X64_CR_CR4] = vmx_vmread(VMCS_GUEST_CR4);
@@ -2906,7 +2926,7 @@
        vmx_vmwrite(VMCS_EXIT_MSR_STORE_COUNT, VMX_MSRLIST_EXIT_NMSR);
 
        /* Set the CR0 mask. Any change of these bits causes a VMEXIT. */
-       vmx_vmwrite(VMCS_CR0_MASK, CR0_STATIC);
+       vmx_vmwrite(VMCS_CR0_MASK, CR0_STATIC_MASK);
 
        /* Force unsupported CR4 fields to zero. */
        vmx_vmwrite(VMCS_CR4_MASK, CR4_INVALID);