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x86/spec_ctrl: Fold the XEN_IBRS_{SET,CLEAR} ALTERNATIVES together

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Currently, the SPEC_CTRL_{ENTRY,EXIT}_* macros encode Xen's choice of
MSR_SPEC_CTRL as an immediate constant, and chooses between IBRS or not by
doubling up the entire alternative block.

There is now a variable holding Xen's choice of value, so use that and
simplify the alternatives.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: af949407ea
master date: 2018-05-16 12:19:10 +0100
This commit is contained in:
Andrew Cooper authored and Jan Beulich committed 2018-05-29 10:59:11 +02:00
1 parent cd5232adbb
commit e7b723bdc1
6 files changed
+35 -53
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xen/arch/x86/cpu/common.c
+2 -6
View File
@@ -359,13 +359,9 @@ void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
if (test_bit(X86_FEATURE_IND_THUNK_JMP,
boot_cpu_data.x86_capability))
__set_bit(X86_FEATURE_IND_THUNK_JMP, c->x86_capability);
if (test_bit(X86_FEATURE_XEN_IBRS_SET,
if (test_bit(X86_FEATURE_SC_MSR,
boot_cpu_data.x86_capability))
__set_bit(X86_FEATURE_XEN_IBRS_SET, c->x86_capability);
if (test_bit(X86_FEATURE_XEN_IBRS_CLEAR,
boot_cpu_data.x86_capability))
__set_bit(X86_FEATURE_XEN_IBRS_CLEAR,
c->x86_capability);
__set_bit(X86_FEATURE_SC_MSR, c->x86_capability);
if (test_bit(X86_FEATURE_RSB_NATIVE,
boot_cpu_data.x86_capability))
__set_bit(X86_FEATURE_RSB_NATIVE, c->x86_capability);
xen/arch/x86/spec_ctrl.c
+5 -7
View File
@@ -114,8 +114,9 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps)
thunk == THUNK_RETPOLINE ? "RETPOLINE" :
thunk == THUNK_LFENCE ? "LFENCE" :
thunk == THUNK_JMP ? "JMP" : "?",
boot_cpu_has(X86_FEATURE_XEN_IBRS_SET) ? " IBRS+" :
boot_cpu_has(X86_FEATURE_XEN_IBRS_CLEAR) ? " IBRS-" : "",
boot_cpu_has(X86_FEATURE_SC_MSR) ?
default_xen_spec_ctrl & SPEC_CTRL_IBRS ? " IBRS+" :
" IBRS-" : "",
opt_ibpb ? " IBPB" : "",
boot_cpu_has(X86_FEATURE_RSB_NATIVE) ? " RSB_NATIVE" : "",
boot_cpu_has(X86_FEATURE_RSB_VMEXIT) ? " RSB_VMEXIT" : "");
@@ -282,13 +283,10 @@ void __init init_speculation_mitigations(void)
* need the IBRS entry/exit logic to virtualise IBRS support for
* guests.
*/
__set_bit(X86_FEATURE_SC_MSR, boot_cpu_data.x86_capability);
if ( ibrs )
{
default_xen_spec_ctrl |= SPEC_CTRL_IBRS;
__set_bit(X86_FEATURE_XEN_IBRS_SET, boot_cpu_data.x86_capability);
}
else
__set_bit(X86_FEATURE_XEN_IBRS_CLEAR, boot_cpu_data.x86_capability);
default_spec_ctrl_flags |= SCF_ist_wrmsr;
}
xen/include/asm-x86/cpufeature.h
+1 -2
View File
@@ -65,8 +65,7 @@
#define X86_FEATURE_IND_THUNK_LFENCE (3*32+ 1) /* Use IND_THUNK_LFENCE */
#define X86_FEATURE_IND_THUNK_JMP (3*32+ 2) /* Use IND_THUNK_JMP */
#define X86_FEATURE_XEN_IBPB (3*32+ 3) /* IBRSB || IBPB */
#define X86_FEATURE_XEN_IBRS_SET (3*32+ 4) /* IBRSB && IRBS set in Xen */
#define X86_FEATURE_XEN_IBRS_CLEAR (3*32+ 5) /* IBRSB && IBRS clear in Xen */
#define X86_FEATURE_SC_MSR (3*32+ 4) /* MSR_SPEC_CTRL used by Xen */
#define X86_FEATURE_RSB_NATIVE (3*32+ 6) /* RSB overwrite needed for native */
#define X86_FEATURE_RSB_VMEXIT (3*32+ 7) /* RSB overwrite needed for vmexit */
#define X86_FEATURE_CONSTANT_TSC (3*32+ 8) /* TSC ticks at a constant rate */
xen/include/asm-x86/nops.h
+3 -3
View File
@@ -61,11 +61,11 @@
#define ASM_NOP7 _ASM_MK_NOP(K8_NOP7)
#define ASM_NOP8 _ASM_MK_NOP(K8_NOP8)
#define ASM_NOP22 ASM_NOP8; ASM_NOP8; ASM_NOP6
#define ASM_NOP23 ASM_NOP8; ASM_NOP8; ASM_NOP7
#define ASM_NOP24 ASM_NOP8; ASM_NOP8; ASM_NOP8
#define ASM_NOP32 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8
#define ASM_NOP36 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP4
#define ASM_NOP25 ASM_NOP8; ASM_NOP8; ASM_NOP7; ASM_NOP2
#define ASM_NOP33 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP7; ASM_NOP2
#define ASM_NOP39 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP7
#define ASM_NOP40 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8
#define ASM_NOP_MAX 8
xen/include/asm-x86/spec_ctrl.h
+9 -5
View File
@@ -52,14 +52,16 @@ static always_inline void spec_ctrl_enter_idle(struct cpu_info *info)
barrier();
info->spec_ctrl_flags |= SCF_use_shadow;
barrier();
asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
:: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", %c3)
:: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0),
"i" (X86_FEATURE_SC_MSR)
: "memory" );
}
/* WARNING! `ret`, `call *`, `jmp *` not safe before this call. */
static always_inline void spec_ctrl_exit_idle(struct cpu_info *info)
{
uint32_t val = SPEC_CTRL_IBRS;
uint32_t val = info->xen_spec_ctrl;
/*
* Disable shadowing before updating the MSR. There are no SMP issues
@@ -67,8 +69,10 @@ static always_inline void spec_ctrl_exit_idle(struct cpu_info *info)
*/
info->spec_ctrl_flags &= ~SCF_use_shadow;
barrier();
asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
:: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", %c3)
:: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0),
"i" (X86_FEATURE_SC_MSR)
: "memory" );
}
#endif /* !__X86_SPEC_CTRL_H__ */
xen/include/asm-x86/spec_ctrl_asm.h
+15 -30
View File
@@ -117,7 +117,7 @@
mov %\tmp, %rsp /* Restore old %rsp */
.endm
.macro DO_SPEC_CTRL_ENTRY_FROM_VMEXIT ibrs_val:req
.macro DO_SPEC_CTRL_ENTRY_FROM_VMEXIT
/*
* Requires %rbx=current, %rsp=regs/cpuinfo
* Clobbers %rax, %rcx, %rdx
@@ -137,11 +137,11 @@
andb $~SCF_use_shadow, CPUINFO_spec_ctrl_flags(%rsp)
/* Load Xen's intended value. */
mov $\ibrs_val, %eax
movzbl CPUINFO_xen_spec_ctrl(%rsp), %eax
wrmsr
.endm
.macro DO_SPEC_CTRL_ENTRY maybexen:req ibrs_val:req
.macro DO_SPEC_CTRL_ENTRY maybexen:req
/*
* Requires %rsp=regs (also cpuinfo if !maybexen)
* Requires %r14=stack_end (if maybexen)
@@ -166,12 +166,12 @@
setnz %al
not %eax
and %al, STACK_CPUINFO_FIELD(spec_ctrl_flags)(%r14)
movzbl STACK_CPUINFO_FIELD(xen_spec_ctrl)(%r14), %eax
.else
andb $~SCF_use_shadow, CPUINFO_spec_ctrl_flags(%rsp)
movzbl CPUINFO_xen_spec_ctrl(%rsp), %eax
.endif
/* Load Xen's intended value. */
mov $\ibrs_val, %eax
wrmsr
.endm
@@ -219,47 +219,32 @@
#define SPEC_CTRL_ENTRY_FROM_VMEXIT \
ALTERNATIVE __stringify(ASM_NOP40), \
DO_OVERWRITE_RSB, X86_FEATURE_RSB_VMEXIT; \
ALTERNATIVE_2 __stringify(ASM_NOP32), \
__stringify(DO_SPEC_CTRL_ENTRY_FROM_VMEXIT \
ibrs_val=SPEC_CTRL_IBRS), \
X86_FEATURE_XEN_IBRS_SET, \
__stringify(DO_SPEC_CTRL_ENTRY_FROM_VMEXIT \
ibrs_val=0), \
X86_FEATURE_XEN_IBRS_CLEAR
ALTERNATIVE __stringify(ASM_NOP33), \
DO_SPEC_CTRL_ENTRY_FROM_VMEXIT, X86_FEATURE_SC_MSR
/* Use after an entry from PV context (syscall/sysenter/int80/int82/etc). */
#define SPEC_CTRL_ENTRY_FROM_PV \
ALTERNATIVE __stringify(ASM_NOP40), \
DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE; \
ALTERNATIVE_2 __stringify(ASM_NOP22), \
__stringify(DO_SPEC_CTRL_ENTRY maybexen=0 \
ibrs_val=SPEC_CTRL_IBRS), \
X86_FEATURE_XEN_IBRS_SET, \
__stringify(DO_SPEC_CTRL_ENTRY maybexen=0 ibrs_val=0), \
X86_FEATURE_XEN_IBRS_CLEAR
ALTERNATIVE __stringify(ASM_NOP25), \
__stringify(DO_SPEC_CTRL_ENTRY maybexen=0), X86_FEATURE_SC_MSR
/* Use in interrupt/exception context. May interrupt Xen or PV context. */
#define SPEC_CTRL_ENTRY_FROM_INTR \
ALTERNATIVE __stringify(ASM_NOP40), \
DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE; \
ALTERNATIVE_2 __stringify(ASM_NOP36), \
__stringify(DO_SPEC_CTRL_ENTRY maybexen=1 \
ibrs_val=SPEC_CTRL_IBRS), \
X86_FEATURE_XEN_IBRS_SET, \
__stringify(DO_SPEC_CTRL_ENTRY maybexen=1 ibrs_val=0), \
X86_FEATURE_XEN_IBRS_CLEAR
ALTERNATIVE __stringify(ASM_NOP39), \
__stringify(DO_SPEC_CTRL_ENTRY maybexen=1), X86_FEATURE_SC_MSR
/* Use when exiting to Xen context. */
#define SPEC_CTRL_EXIT_TO_XEN \
ALTERNATIVE_2 __stringify(ASM_NOP23), \
DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_XEN_IBRS_SET, \
DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_XEN_IBRS_CLEAR
ALTERNATIVE __stringify(ASM_NOP23), \
DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_SC_MSR
/* Use when exiting to guest context. */
#define SPEC_CTRL_EXIT_TO_GUEST \
ALTERNATIVE_2 __stringify(ASM_NOP24), \
DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_XEN_IBRS_SET, \
DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_XEN_IBRS_CLEAR
ALTERNATIVE __stringify(ASM_NOP24), \
DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR
/* TODO: Drop these when the alternatives infrastructure is NMI/#MC safe. */
.macro SPEC_CTRL_ENTRY_FROM_INTR_IST
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