We don't do compat32 so MSR_CSTAR shouldn't be set up: delete the

Xsyscall32 stub and UCODE32 selector, set MSR_CSTAR to zero at CPU
startup, and rezero on ACPI resume and VM exit.

requested a while ago by deraadt@
AMD VM testing chris@
testing and ok krw@

diff --git a/sys/arch/amd64/amd64/acpi_wakecode.S b/sys/arch/amd64/amd64/acpi_wakecode.S
index ddcdc74..da47597 100644 (file)
--- a/sys/arch/amd64/amd64/acpi_wakecode.S
+++ b/sys/arch/amd64/amd64/acpi_wakecode.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: acpi_wakecode.S,v 1.49 2022/12/01 00:26:15 guenther Exp $ */
+/* $OpenBSD: acpi_wakecode.S,v 1.50 2024/02/25 22:33:09 guenther Exp $ */
 /*
  * Copyright (c) 2001 Takanori Watanabe <takawata@jp.freebsd.org>
  * Copyright (c) 2001 Mitsuru IWASAKI <iwasaki@jp.freebsd.org>
@@ -267,8 +267,8 @@ _ACPI_TRMP_LABEL(.Lacpi_long_mode_trampoline)
        wrmsr
 
        movl    $MSR_CSTAR, %ecx
-       movl    .Lacpi_saved_cstar, %eax
-       movl    .Lacpi_saved_cstar+4, %edx
+       xorl    %eax, %eax
+       xorl    %edx, %edx
        wrmsr
 
        movl    $MSR_SFMASK, %ecx
@@ -691,8 +691,6 @@ _ACPI_TRMP_DATA_LABEL(.Lacpi_saved_star)
        .quad 0
 _ACPI_TRMP_DATA_LABEL(.Lacpi_saved_lstar)
        .quad 0
-_ACPI_TRMP_DATA_LABEL(.Lacpi_saved_cstar)
-       .quad 0
 _ACPI_TRMP_DATA_LABEL(.Lacpi_saved_sfmask)
        .quad 0
 #if NLAPIC > 0
@@ -781,11 +779,6 @@ NENTRY(acpi_savecpu)
        movl    %eax, .Lacpi_saved_star
        movl    %edx, .Lacpi_saved_star+4
 
-       movl    $MSR_CSTAR, %ecx
-       rdmsr
-       movl    %eax, .Lacpi_saved_cstar
-       movl    %edx, .Lacpi_saved_cstar+4
-
        movl    $MSR_LSTAR, %ecx
        rdmsr
        movl    %eax, .Lacpi_saved_lstar

diff --git a/sys/arch/amd64/amd64/cpu.c b/sys/arch/amd64/amd64/cpu.c
index 6c8e2b6..7f4cccf 100644 (file)
--- a/sys/arch/amd64/amd64/cpu.c
+++ b/sys/arch/amd64/amd64/cpu.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: cpu.c,v 1.182 2024/02/24 17:00:05 deraadt Exp $       */
+/*     $OpenBSD: cpu.c,v 1.183 2024/02/25 22:33:09 guenther Exp $      */
 /* $NetBSD: cpu.c,v 1.1 2003/04/26 18:39:26 fvdl Exp $ */
 
 /*-
@@ -1184,10 +1184,10 @@ cpu_init_msrs(struct cpu_info *ci)
 {
        wrmsr(MSR_STAR,
            ((uint64_t)GSEL(GCODE_SEL, SEL_KPL) << 32) |
-           ((uint64_t)GSEL(GUCODE32_SEL, SEL_UPL) << 48));
+           ((uint64_t)GSEL(GUDATA_SEL-1, SEL_UPL) << 48));
        wrmsr(MSR_LSTAR, cpu_meltdown ? (uint64_t)Xsyscall_meltdown :
            (uint64_t)Xsyscall);
-       wrmsr(MSR_CSTAR, (uint64_t)Xsyscall32);
+       wrmsr(MSR_CSTAR, 0);
        wrmsr(MSR_SFMASK, PSL_NT|PSL_T|PSL_I|PSL_C|PSL_D|PSL_AC);
 
        wrmsr(MSR_FSBASE, 0);

diff --git a/sys/arch/amd64/amd64/locore.S b/sys/arch/amd64/amd64/locore.S
index 1365cf9..3531114 100644 (file)
--- a/sys/arch/amd64/amd64/locore.S
+++ b/sys/arch/amd64/amd64/locore.S
@@ -1,4 +1,4 @@
-/*     $OpenBSD: locore.S,v 1.145 2024/02/12 01:18:17 guenther Exp $   */
+/*     $OpenBSD: locore.S,v 1.146 2024/02/25 22:33:09 guenther Exp $   */
 /*     $NetBSD: locore.S,v 1.13 2004/03/25 18:33:17 drochner Exp $     */
 
 /*
@@ -507,11 +507,6 @@ ENTRY(savectx)
        lfence
 END(savectx)
 
-// XXX this should not behave like a nop
-IDTVEC(syscall32)
-       sysret          /* go away please */
-END(Xsyscall32)
-
 /*
  * syscall insn entry.
  * Enter here with interrupts blocked; %rcx contains the caller's

diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 9fa994b..f58e6c5 100644 (file)
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: machdep.c,v 1.290 2024/02/03 16:21:22 deraadt Exp $   */
+/*     $OpenBSD: machdep.c,v 1.291 2024/02/25 22:33:09 guenther Exp $  */
 /*     $NetBSD: machdep.c,v 1.3 2003/05/07 22:58:18 fvdl Exp $ */
 
 /*-
@@ -1744,9 +1744,6 @@ init_x86_64(paddr_t first_avail)
        set_mem_segment(GDT_ADDR_MEM(cpu_info_primary.ci_gdt, GDATA_SEL), 0,
            0xfffff, SDT_MEMRWA, SEL_KPL, 1, 0, 1);
 
-       set_mem_segment(GDT_ADDR_MEM(cpu_info_primary.ci_gdt, GUCODE32_SEL), 0,
-           atop(VM_MAXUSER_ADDRESS32) - 1, SDT_MEMERA, SEL_UPL, 1, 1, 0);
-
        set_mem_segment(GDT_ADDR_MEM(cpu_info_primary.ci_gdt, GUDATA_SEL), 0,
            atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMRWA, SEL_UPL, 1, 0, 1);
 

diff --git a/sys/arch/amd64/amd64/vmm_machdep.c b/sys/arch/amd64/amd64/vmm_machdep.c
index 7cc3759..943797d 100644 (file)
--- a/sys/arch/amd64/amd64/vmm_machdep.c
+++ b/sys/arch/amd64/amd64/vmm_machdep.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: vmm_machdep.c,v 1.18 2024/02/12 02:57:14 jsg Exp $ */
+/* $OpenBSD: vmm_machdep.c,v 1.19 2024/02/25 22:33:09 guenther Exp $ */
 /*
  * Copyright (c) 2014 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -2734,7 +2734,7 @@ vcpu_reset_regs_vmx(struct vcpu *vcpu, struct vcpu_reg_state *vrs)
        msr_store[2].vms_index = MSR_LSTAR;
        msr_store[2].vms_data = rdmsr(MSR_LSTAR);
        msr_store[3].vms_index = MSR_CSTAR;
-       msr_store[3].vms_data = rdmsr(MSR_CSTAR);
+       msr_store[3].vms_data = 0;
        msr_store[4].vms_index = MSR_SFMASK;
        msr_store[4].vms_data = rdmsr(MSR_SFMASK);
        msr_store[5].vms_index = MSR_KERNELGSBASE;

diff --git a/sys/arch/amd64/amd64/vmm_support.S b/sys/arch/amd64/amd64/vmm_support.S
index 7b7d9f2..aadfb4a 100644 (file)
--- a/sys/arch/amd64/amd64/vmm_support.S
+++ b/sys/arch/amd64/amd64/vmm_support.S
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vmm_support.S,v 1.24 2023/11/28 00:17:48 dv Exp $     */
+/*     $OpenBSD: vmm_support.S,v 1.25 2024/02/25 22:33:09 guenther Exp $       */
 /*
  * Copyright (c) 2014 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -225,12 +225,6 @@ skip_init:
        pushq   %rax
        pushq   %rdx
 
-       /* XXX - unused? */
-       movq    $MSR_CSTAR, %rcx
-       rdmsr
-       pushq   %rax
-       pushq   %rdx
-
        movq    $MSR_SFMASK, %rcx
        rdmsr
        pushq   %rax
@@ -483,9 +477,9 @@ restore_host:
        movq    $MSR_SFMASK, %rcx
        wrmsr
 
-       /* XXX - unused? */
-       popq    %rdx
-       popq    %rax
+       /* make sure guest doesn't bleed into host */
+       xorl    %edx, %edx
+       xorl    %eax, %eax
        movq    $MSR_CSTAR, %rcx
        wrmsr
 
@@ -584,12 +578,6 @@ ENTRY(svm_enter_guest)
        pushq   %rax
        pushq   %rdx
 
-       /* XXX - unused? */
-       movq    $MSR_CSTAR, %rcx
-       rdmsr
-       pushq   %rax
-       pushq   %rdx
-
        movq    $MSR_SFMASK, %rcx
        rdmsr
        pushq   %rax
@@ -696,9 +684,9 @@ restore_host_svm:
        movq    $MSR_SFMASK, %rcx
        wrmsr
 
-       /* XXX - unused? */
-       popq    %rdx
-       popq    %rax
+       /* make sure guest doesn't bleed into host */
+       xorl    %edx, %edx
+       xorl    %eax, %eax
        movq    $MSR_CSTAR, %rcx
        wrmsr
 

diff --git a/sys/arch/amd64/include/segments.h b/sys/arch/amd64/include/segments.h
index 87de2c0..308639a 100644 (file)
--- a/sys/arch/amd64/include/segments.h
+++ b/sys/arch/amd64/include/segments.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: segments.h,v 1.16 2024/01/19 18:38:16 kettenis Exp $  */
+/*     $OpenBSD: segments.h,v 1.17 2024/02/25 22:33:09 guenther Exp $  */
 /*     $NetBSD: segments.h,v 1.1 2003/04/26 18:39:47 fvdl Exp $        */
 
 /*-
@@ -247,16 +247,15 @@ void cpu_init_idt(void);
  * Then comes the predefined TSS descriptor.
  * There are NGDT_SYS of them.
  *
- * The particular order of the UCODE32, UDATA, and UCODE descriptors is 
- * required by the syscall/sysret instructions.
+ * The particular order of the UDATA and UCODE descriptors is 
+ * required by the sysretq instruction.
  */
 #define        GNULL_SEL       0       /* Null descriptor */
 #define        GCODE_SEL       1       /* Kernel code descriptor */
 #define        GDATA_SEL       2       /* Kernel data descriptor */
-#define        GUCODE32_SEL    3       /* User 32bit code descriptor (unused) */
-#define        GUDATA_SEL      4       /* User data descriptor */
-#define        GUCODE_SEL      5       /* User code descriptor */
-#define NGDT_MEM 6
+#define        GUDATA_SEL      3       /* User data descriptor */
+#define        GUCODE_SEL      4       /* User code descriptor */
+#define NGDT_MEM 5
 
 #define        GPROC0_SEL      0       /* common TSS */
 #define NGDT_SYS       1