[src/trunk]: src/sys/dev/nvmm/x86 Optimize:

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

details:   https://anonhg.NetBSD.org/src/rev/e48225609fdb
branches:  trunk
changeset: 447413:e48225609fdb
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu Jan 10 06:58:36 2019 +0000

description:
Optimize:

 * Don't save/restore the host CR2, we don't care because we're not in a
   #PF context (and preemption switches already handle CR2 safely).

 * Don't save/restore the host FS and GS, just reset them to zero after
   VMRUN. Note: DS and ES must be reset _before_ VMRUN, but that doesn't
   apply to FS and GS.

 * Handle FSBASE and KGSBASE outside of the VCPU loop, to avoid the cost
   of saving/restoring them when there's no reason to leave the loop.

diffstat:

 sys/dev/nvmm/x86/nvmm_x86_svm.c     |  19 ++++++++-----------
 sys/dev/nvmm/x86/nvmm_x86_svmfunc.S |  34 ++++++++--------------------------
 2 files changed, 16 insertions(+), 37 deletions(-)

diffs (131 lines):

diff -r 2781d046ec38 -r e48225609fdb sys/dev/nvmm/x86/nvmm_x86_svm.c
--- a/sys/dev/nvmm/x86/nvmm_x86_svm.c   Thu Jan 10 06:31:04 2019 +0000
+++ b/sys/dev/nvmm/x86/nvmm_x86_svm.c   Thu Jan 10 06:58:36 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: nvmm_x86_svm.c,v 1.13 2019/01/08 14:43:18 maxv Exp $   */
+/*     $NetBSD: nvmm_x86_svm.c,v 1.14 2019/01/10 06:58:36 maxv Exp $   */
 
 /*
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: nvmm_x86_svm.c,v 1.13 2019/01/08 14:43:18 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: nvmm_x86_svm.c,v 1.14 2019/01/10 06:58:36 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -521,7 +521,8 @@
        uint64_t lstar;
        uint64_t cstar;
        uint64_t sfmask;
-       uint64_t cr2;
+       uint64_t fsbase;
+       uint64_t kernelgsbase;
        bool ts_set;
        struct xsave_header hfpu __aligned(16);
 
@@ -1151,14 +1152,12 @@
 {
        struct svm_cpudata *cpudata = vcpu->cpudata;
 
-       /* Save the fixed Host MSRs. */
        cpudata->star = rdmsr(MSR_STAR);
        cpudata->lstar = rdmsr(MSR_LSTAR);
        cpudata->cstar = rdmsr(MSR_CSTAR);
        cpudata->sfmask = rdmsr(MSR_SFMASK);
-
-       /* Save the Host CR2. */
-       cpudata->cr2 = rcr2();
+       cpudata->fsbase = rdmsr(MSR_FSBASE);
+       cpudata->kernelgsbase = rdmsr(MSR_KERNELGSBASE);
 }
 
 static void
@@ -1166,14 +1165,12 @@
 {
        struct svm_cpudata *cpudata = vcpu->cpudata;
 
-       /* Restore the fixed Host MSRs. */
        wrmsr(MSR_STAR, cpudata->star);
        wrmsr(MSR_LSTAR, cpudata->lstar);
        wrmsr(MSR_CSTAR, cpudata->cstar);
        wrmsr(MSR_SFMASK, cpudata->sfmask);
-
-       /* Restore the Host CR2. */
-       lcr2(cpudata->cr2);
+       wrmsr(MSR_FSBASE, cpudata->fsbase);
+       wrmsr(MSR_KERNELGSBASE, cpudata->kernelgsbase);
 }
 
 static int
diff -r 2781d046ec38 -r e48225609fdb sys/dev/nvmm/x86/nvmm_x86_svmfunc.S
--- a/sys/dev/nvmm/x86/nvmm_x86_svmfunc.S       Thu Jan 10 06:31:04 2019 +0000
+++ b/sys/dev/nvmm/x86/nvmm_x86_svmfunc.S       Thu Jan 10 06:58:36 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: nvmm_x86_svmfunc.S,v 1.1 2018/11/07 07:43:08 maxv Exp $        */
+/*     $NetBSD: nvmm_x86_svmfunc.S,v 1.2 2019/01/10 06:58:36 maxv Exp $        */
 
 /*
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -73,14 +73,6 @@
        movq    $msr,%rcx       ;\
        wrmsr
 
-#define HOST_SAVE_SEGREG(sreg) \
-       movw    sreg,%ax        ;\
-       pushw   %ax
-
-#define HOST_RESTORE_SEGREG(sreg)\
-       popw    %ax             ;\
-       movw    %ax,sreg
-
 #define HOST_SAVE_TR           \
        strw    %ax             ;\
        pushw   %ax
@@ -150,22 +142,13 @@
        /* Save the Host TR. */
        HOST_SAVE_TR
 
-       /* Save the variable Host MSRs. */
-       HOST_SAVE_MSR(MSR_KERNELGSBASE)
+       /* Save the Host GSBASE. */
        HOST_SAVE_MSR(MSR_GSBASE)
-       HOST_SAVE_MSR(MSR_FSBASE)
 
-       /* Reset the Host Segregs. */
+       /* Reset DS and ES. */
        movq    $GSEL(GUDATA_SEL, SEL_UPL),%rax
        movw    %ax,%ds
        movw    %ax,%es
-       xorq    %rax,%rax
-       movw    %ax,%fs
-       movw    %ax,%gs
-
-       /* Save some Host Segregs. */
-       HOST_SAVE_SEGREG(%fs)
-       HOST_SAVE_SEGREG(%gs)
 
        /* Save the Host LDT. */
        HOST_SAVE_LDT
@@ -195,14 +178,13 @@
        /* Restore the Host LDT. */
        HOST_RESTORE_LDT
 
-       /* Restore the Host Segregs. */
-       HOST_RESTORE_SEGREG(%gs)
-       HOST_RESTORE_SEGREG(%fs)
+       /* Reset FS and GS. */
+       xorq    %rax,%rax
+       movw    %ax,%fs
+       movw    %ax,%gs
 
-       /* Restore the variable Host MSRs. */
-       HOST_RESTORE_MSR(MSR_FSBASE)
+       /* Restore the Host GSBASE. */
        HOST_RESTORE_MSR(MSR_GSBASE)
-       HOST_RESTORE_MSR(MSR_KERNELGSBASE)
 
        /* Restore the Host TR. */
        HOST_RESTORE_TR