[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/821147bd5f9a
branches:  trunk
changeset: 938221:821147bd5f9a
user:      maxv <maxv%NetBSD.org@localhost>
date:      Fri Sep 04 17:07:33 2020 +0000

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

 - Flush the guest TLB when certain CR0 bits change.
 - If the guest updates a static bit in CR0, then reflect the change in
   VMCS_CR0_SHADOW, for the guest to get the illusion that the change was
   applied. The "real" CR0 static bits remain unchanged.
 - In vmx_vcpu_{g,s}et_state(), take VMCS_CR0_SHADOW into account.
 - Slightly modify the CR4 handling code, just for more symmetry with CR0.

diffstat:

 sys/dev/nvmm/x86/nvmm_x86_vmx.c |  31 ++++++++++++++++++++++---------
 1 files changed, 22 insertions(+), 9 deletions(-)

diffs (101 lines):

diff -r 715b05ed619c -r 821147bd5f9a sys/dev/nvmm/x86/nvmm_x86_vmx.c
--- a/sys/dev/nvmm/x86/nvmm_x86_vmx.c   Fri Sep 04 17:06:23 2020 +0000
+++ b/sys/dev/nvmm/x86/nvmm_x86_vmx.c   Fri Sep 04 17:07:33 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: nvmm_x86_vmx.c,v 1.74 2020/08/26 16:32:02 maxv Exp $   */
+/*     $NetBSD: nvmm_x86_vmx.c,v 1.75 2020/09/04 17:07:33 maxv Exp $   */
 
 /*
  * Copyright (c) 2018-2020 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: nvmm_x86_vmx.c,v 1.74 2020/08/26 16:32:02 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: nvmm_x86_vmx.c,v 1.75 2020/09/04 17:07:33 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -729,6 +729,9 @@
 #define MSRBM_NPAGES   1
 #define MSRBM_SIZE     (MSRBM_NPAGES * PAGE_SIZE)
 
+#define CR0_STATIC \
+       (CR0_NW|CR0_CD|CR0_ET)
+
 #define CR4_VALID \
        (CR4_VME |                      \
         CR4_PVI |                      \
@@ -1570,7 +1573,7 @@
     uint64_t qual)
 {
        struct vmx_cpudata *cpudata = vcpu->cpudata;
-       uint64_t type, gpr, cr0;
+       uint64_t type, gpr, oldcr0, cr0;
        uint64_t efer, ctls1;
 
        type = __SHIFTOUT(qual, VMX_QUAL_CR_TYPE);
@@ -1613,6 +1616,13 @@
                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) {
+               cpudata->gtlb_want_flush = true;
+       }
+
+       vmx_vmwrite(VMCS_CR0_SHADOW, gpr);
        vmx_vmwrite(VMCS_GUEST_CR0, cr0);
        vmx_inkernel_advance();
        return 0;
@@ -1623,7 +1633,7 @@
     uint64_t qual)
 {
        struct vmx_cpudata *cpudata = vcpu->cpudata;
-       uint64_t type, gpr, cr4;
+       uint64_t type, gpr, oldcr4, cr4;
 
        type = __SHIFTOUT(qual, VMX_QUAL_CR_TYPE);
        if (type != CR_TYPE_WRITE) {
@@ -1647,7 +1657,8 @@
                return -1;
        }
 
-       if ((vmx_vmread(VMCS_GUEST_CR4) ^ cr4) & CR4_TLB_FLUSH) {
+       oldcr4 = vmx_vmread(VMCS_GUEST_CR4);
+       if ((oldcr4 ^ gpr) & CR4_TLB_FLUSH) {
                cpudata->gtlb_want_flush = true;
        }
 
@@ -2566,6 +2577,7 @@
                /*
                 * CR0_NE and CR4_VMXE are mandatory.
                 */
+               vmx_vmwrite(VMCS_CR0_SHADOW, state->crs[NVMM_X64_CR_CR0]);
                vmx_vmwrite(VMCS_GUEST_CR0,
                    state->crs[NVMM_X64_CR_CR0] | CR0_NE);
                cpudata->gcr2 = state->crs[NVMM_X64_CR_CR2];
@@ -2703,7 +2715,9 @@
        }
 
        if (flags & NVMM_X64_STATE_CRS) {
-               state->crs[NVMM_X64_CR_CR0] = vmx_vmread(VMCS_GUEST_CR0);
+               state->crs[NVMM_X64_CR_CR0] =
+                   (vmx_vmread(VMCS_CR0_SHADOW) & CR0_STATIC) |
+                   (vmx_vmread(VMCS_GUEST_CR0) & ~CR0_STATIC);
                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);
@@ -2892,9 +2906,8 @@
        vmx_vmwrite(VMCS_ENTRY_MSR_LOAD_COUNT, vmx_msrlist_entry_nmsr);
        vmx_vmwrite(VMCS_EXIT_MSR_STORE_COUNT, VMX_MSRLIST_EXIT_NMSR);
 
-       /* Force CR0_NW and CR0_CD to zero, CR0_ET to one. */
-       vmx_vmwrite(VMCS_CR0_MASK, CR0_NW|CR0_CD|CR0_ET);
-       vmx_vmwrite(VMCS_CR0_SHADOW, CR0_ET);
+       /* Set the CR0 mask. Any change of these bits causes a VMEXIT. */
+       vmx_vmwrite(VMCS_CR0_MASK, CR0_STATIC);
 
        /* Force unsupported CR4 fields to zero. */
        vmx_vmwrite(VMCS_CR4_MASK, CR4_INVALID);