[src/trunk]: src/sys/arch/x86/x86 Change the effect of SVS on the TLB. Keep C...

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

details:   https://anonhg.NetBSD.org/src/rev/0fc3ae77f7e7
branches:  trunk
changeset: 451558:0fc3ae77f7e7
user:      maxv <maxv%NetBSD.org@localhost>
date:      Mon May 27 18:36:37 2019 +0000

description:
Change the effect of SVS on the TLB. Keep CR4_PGE set when SVS is enabled,
but don't use PTE_G on the kernel PTEs in general.

Add PTE_G on only a few pages, that are already leaked to userland and do
not contain secrets.

This slightly improves syscall performance.

diffstat:

 sys/arch/x86/x86/cpu.c  |   7 ++-----
 sys/arch/x86/x86/pmap.c |  11 ++++++++---
 sys/arch/x86/x86/svs.c  |  33 ++++++++++++++++++++++-----------
 3 files changed, 32 insertions(+), 19 deletions(-)

diffs (157 lines):

diff -r ce9ba8f9a4f1 -r 0fc3ae77f7e7 sys/arch/x86/x86/cpu.c
--- a/sys/arch/x86/x86/cpu.c    Mon May 27 17:32:36 2019 +0000
+++ b/sys/arch/x86/x86/cpu.c    Mon May 27 18:36:37 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cpu.c,v 1.169 2019/05/27 17:32:36 maxv Exp $   */
+/*     $NetBSD: cpu.c,v 1.170 2019/05/27 18:36:37 maxv Exp $   */
 
 /*
  * Copyright (c) 2000-2012 NetBSD Foundation, Inc.
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: cpu.c,v 1.169 2019/05/27 17:32:36 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: cpu.c,v 1.170 2019/05/27 18:36:37 maxv Exp $");
 
 #include "opt_ddb.h"
 #include "opt_mpbios.h"                /* for MPDEBUG */
@@ -586,9 +586,6 @@
 
        /* If global TLB caching is supported, enable it */
        if (cpu_feature[0] & CPUID_PGE)
-#ifdef SVS
-               if (!svs_enabled)
-#endif
                cr4 |= CR4_PGE;
 
        /*
diff -r ce9ba8f9a4f1 -r 0fc3ae77f7e7 sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Mon May 27 17:32:36 2019 +0000
+++ b/sys/arch/x86/x86/pmap.c   Mon May 27 18:36:37 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.332 2019/05/27 17:32:36 maxv Exp $  */
+/*     $NetBSD: pmap.c,v 1.333 2019/05/27 18:36:37 maxv Exp $  */
 
 /*
  * Copyright (c) 2008, 2010, 2016, 2017 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.332 2019/05/27 17:32:36 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.333 2019/05/27 18:36:37 maxv Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -1117,12 +1117,17 @@
 #if !defined(XENPV)
        /*
         * Begin to enable global TLB entries if they are supported: add PTE_G
-        * attribute to already mapped kernel pages.
+        * attribute to already mapped kernel pages. Do that only if SVS is
+        * disabled.
         *
         * The G bit has no effect until the CR4_PGE bit is set in CR4, which
         * happens later in cpu_init().
         */
+#ifdef SVS
+       if (!svs_enabled && (cpu_feature[0] & CPUID_PGE)) {
+#else
        if (cpu_feature[0] & CPUID_PGE) {
+#endif
                pmap_pg_g = PTE_G;
                pmap_remap_global();
        }
diff -r ce9ba8f9a4f1 -r 0fc3ae77f7e7 sys/arch/x86/x86/svs.c
--- a/sys/arch/x86/x86/svs.c    Mon May 27 17:32:36 2019 +0000
+++ b/sys/arch/x86/x86/svs.c    Mon May 27 18:36:37 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: svs.c,v 1.27 2019/05/27 17:32:36 maxv Exp $    */
+/*     $NetBSD: svs.c,v 1.28 2019/05/27 18:36:37 maxv Exp $    */
 
 /*
  * Copyright (c) 2018-2019 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: svs.c,v 1.27 2019/05/27 17:32:36 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: svs.c,v 1.28 2019/05/27 18:36:37 maxv Exp $");
 
 #include "opt_svs.h"
 
@@ -268,7 +268,7 @@
 }
 
 static void
-svs_page_add(struct cpu_info *ci, vaddr_t va)
+svs_page_add(struct cpu_info *ci, vaddr_t va, bool global)
 {
        pd_entry_t *srcpde, *dstpde, pde;
        size_t idx, pidx;
@@ -289,9 +289,10 @@
                panic("%s: L2 page not mapped", __func__);
        }
        if (srcpde[idx] & PTE_PS) {
+               KASSERT(!global);
                pa = srcpde[idx] & PTE_2MFRAME;
                pa += (paddr_t)(va % NBPD_L2);
-               pde = (srcpde[idx] & ~(PTE_G|PTE_PS|PTE_2MFRAME)) | pa;
+               pde = (srcpde[idx] & ~(PTE_PS|PTE_2MFRAME)) | pa;
 
                if (pmap_valid_entry(dstpde[pidx])) {
                        panic("%s: L1 page already mapped", __func__);
@@ -311,7 +312,17 @@
        if (pmap_valid_entry(dstpde[pidx])) {
                panic("%s: L1 page already mapped", __func__);
        }
-       dstpde[pidx] = srcpde[idx] & ~(PTE_G);
+       dstpde[pidx] = srcpde[idx];
+
+       /*
+        * If we want a global translation, mark both the src and dst with
+        * PTE_G.
+        */
+       if (global) {
+               srcpde[idx] |= PTE_G;
+               dstpde[pidx] |= PTE_G;
+               tlbflushg();
+       }
 }
 
 static void
@@ -394,14 +405,14 @@
 }
 
 static void
-svs_range_add(struct cpu_info *ci, vaddr_t va, size_t size)
+svs_range_add(struct cpu_info *ci, vaddr_t va, size_t size, bool global)
 {
        size_t i, n;
 
        KASSERT(size % PAGE_SIZE == 0);
        n = size / PAGE_SIZE;
        for (i = 0; i < n; i++) {
-               svs_page_add(ci, va + i * PAGE_SIZE);
+               svs_page_add(ci, va + i * PAGE_SIZE, global);
        }
 }
 
@@ -434,12 +445,12 @@
 
        mutex_init(&ci->ci_svs_mtx, MUTEX_DEFAULT, IPL_VM);
 
-       svs_page_add(ci, (vaddr_t)&pcpuarea->idt);
-       svs_page_add(ci, (vaddr_t)&pcpuarea->ldt);
+       svs_page_add(ci, (vaddr_t)&pcpuarea->idt, true);
+       svs_page_add(ci, (vaddr_t)&pcpuarea->ldt, true);
        svs_range_add(ci, (vaddr_t)&pcpuarea->ent[cid],
-           offsetof(struct pcpu_entry, rsp0));
+           offsetof(struct pcpu_entry, rsp0), true);
        svs_range_add(ci, (vaddr_t)&__text_user_start,
-           (vaddr_t)&__text_user_end - (vaddr_t)&__text_user_start);
+           (vaddr_t)&__text_user_end - (vaddr_t)&__text_user_start, false);
 
        svs_rsp0_init(ci);
        svs_utls_init(ci);