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x86/bugs: Add a Transient Scheduler Attacks mitigation

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commit d8010d4ba4 upstream.

Add the required features detection glue to bugs.c et all in order to
support the TSA mitigation.

Co-developed-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Borislav Petkov (AMD) 2024-09-11 10:53:08 +02:00 committed by Greg Kroah-Hartman
parent 04304f5fe3
commit f2b75f1368
14 changed files with 260 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/ABI/testing/sysfs-devices-system-cpu
View File

@ -524,6 +524,7 @@ What: /sys/devices/system/cpu/vulnerabilities
/sys/devices/system/cpu/vulnerabilities/spectre_v1
/sys/devices/system/cpu/vulnerabilities/spectre_v2
/sys/devices/system/cpu/vulnerabilities/srbds
/sys/devices/system/cpu/vulnerabilities/tsa
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort
Date: January 2018
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>

13
Documentation/admin-guide/kernel-parameters.txt
View File

@ -5990,6 +5990,19 @@
If not specified, "default" is used. In this case,
the RNG's choice is left to each individual trust source.
tsa= [X86] Control mitigation for Transient Scheduler
Attacks on AMD CPUs. Search the following in your
favourite search engine for more details:
"Technical guidance for mitigating transient scheduler
attacks".
off - disable the mitigation
on - enable the mitigation (default)
user - mitigate only user/kernel transitions
vm - mitigate only guest/host transitions
tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this

9
arch/x86/Kconfig
View File

@ -2528,6 +2528,15 @@ config MITIGATION_ITS
disabled, mitigation cannot be enabled via cmdline.
See <file:Documentation/admin-guide/hw-vuln/indirect-target-selection.rst>
config MITIGATION_TSA
bool "Mitigate Transient Scheduler Attacks"
depends on CPU_SUP_AMD
default y
help
Enable mitigation for Transient Scheduler Attacks. TSA is a hardware
security vulnerability on AMD CPUs which can lead to forwarding of
invalid info to subsequent instructions and thus can affect their
timing and thereby cause a leakage.
endif
config ARCH_HAS_ADD_PAGES

13
arch/x86/include/asm/cpu.h
View File

@ -72,4 +72,17 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
#else
static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {}
#endif
union zen_patch_rev {
struct {
__u32 rev : 8,
stepping : 4,
model : 4,
__reserved : 4,
ext_model : 4,
ext_fam : 8;
};
__u32 ucode_rev;
};
#endif /* _ASM_X86_CPU_H */

6
arch/x86/include/asm/cpufeatures.h
View File

@ -419,6 +419,7 @@
#define X86_FEATURE_SME_COHERENT (19*32+10) /* "" AMD hardware-enforced cache coherency */
#define X86_FEATURE_AUTOIBRS (20*32+ 8) /* "" Automatic IBRS */
#define X86_FEATURE_VERW_CLEAR (20*32+ 10) /* "" The memory form of VERW mitigates TSA */
#define X86_FEATURE_SBPB (20*32+27) /* "" Selective Branch Prediction Barrier */
#define X86_FEATURE_IBPB_BRTYPE (20*32+28) /* "" MSR_PRED_CMD[IBPB] flushes all branch type predictions */
#define X86_FEATURE_SRSO_NO (20*32+29) /* "" CPU is not affected by SRSO */
@ -435,6 +436,10 @@
#define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */
#define X86_FEATURE_INDIRECT_THUNK_ITS (21*32 + 5) /* "" Use thunk for indirect branches in lower half of cacheline */
#define X86_FEATURE_TSA_SQ_NO (21*32+11) /* "" AMD CPU not vulnerable to TSA-SQ */
#define X86_FEATURE_TSA_L1_NO (21*32+12) /* "" AMD CPU not vulnerable to TSA-L1 */
#define X86_FEATURE_CLEAR_CPU_BUF_VM (21*32+13) /* "" Clear CPU buffers using VERW before VMRUN */
/*
* BUG word(s)
*/
@ -486,4 +491,5 @@
#define X86_BUG_IBPB_NO_RET X86_BUG(1*32 + 4) /* "ibpb_no_ret" IBPB omits return target predictions */
#define X86_BUG_ITS X86_BUG(1*32 + 5) /* CPU is affected by Indirect Target Selection */
#define X86_BUG_ITS_NATIVE_ONLY X86_BUG(1*32 + 6) /* CPU is affected by ITS, VMX is not affected */
#define X86_BUG_TSA X86_BUG(1*32+ 9) /* "tsa" CPU is affected by Transient Scheduler Attacks */
#endif /* _ASM_X86_CPUFEATURES_H */

2
arch/x86/include/asm/mwait.h
View File

@ -79,7 +79,7 @@ static inline void __mwait(unsigned long eax, unsigned long ecx)
static inline void __mwaitx(unsigned long eax, unsigned long ebx,
unsigned long ecx)
{
/* No MDS buffer clear as this is AMD/HYGON only */
/* No need for TSA buffer clearing on AMD */
/* "mwaitx %eax, %ebx, %ecx;" */
asm volatile(".byte 0x0f, 0x01, 0xfb;"

12
arch/x86/include/asm/nospec-branch.h
View File

@ -208,8 +208,8 @@
* CFLAGS.ZF.
* Note: Only the memory operand variant of VERW clears the CPU buffers.
*/
.macro CLEAR_CPU_BUFFERS
ALTERNATIVE "jmp .Lskip_verw_\@", "", X86_FEATURE_CLEAR_CPU_BUF
.macro __CLEAR_CPU_BUFFERS feature
ALTERNATIVE "jmp .Lskip_verw_\@", "", \feature
#ifdef CONFIG_X86_64
verw x86_verw_sel(%rip)
#else
@ -223,6 +223,12 @@
.Lskip_verw_\@:
.endm
#define CLEAR_CPU_BUFFERS \
__CLEAR_CPU_BUFFERS X86_FEATURE_CLEAR_CPU_BUF
#define VM_CLEAR_CPU_BUFFERS \
__CLEAR_CPU_BUFFERS X86_FEATURE_CLEAR_CPU_BUF_VM
#ifdef CONFIG_X86_64
.macro CLEAR_BRANCH_HISTORY
ALTERNATIVE "", "call clear_bhb_loop", X86_FEATURE_CLEAR_BHB_LOOP
@ -464,7 +470,7 @@ static __always_inline void x86_clear_cpu_buffers(void)
/**
* x86_idle_clear_cpu_buffers - Buffer clearing support in idle for the MDS
* vulnerability
* and TSA vulnerabilities.
*
* Clear CPU buffers if the corresponding static key is enabled
*/

58
arch/x86/kernel/cpu/amd.c
View File

@ -582,6 +582,61 @@ static void early_init_amd_mc(struct cpuinfo_x86 *c)
#endif
}
static bool amd_check_tsa_microcode(void)
{
struct cpuinfo_x86 *c = &boot_cpu_data;
union zen_patch_rev p;
u32 min_rev = 0;
p.ext_fam = c->x86 - 0xf;
p.model = c->x86_model;
p.stepping = c->x86_stepping;
if (c->x86 == 0x19) {
switch (p.ucode_rev >> 8) {
case 0xa0011: min_rev = 0x0a0011d7; break;
case 0xa0012: min_rev = 0x0a00123b; break;
case 0xa0082: min_rev = 0x0a00820d; break;
case 0xa1011: min_rev = 0x0a10114c; break;
case 0xa1012: min_rev = 0x0a10124c; break;
case 0xa1081: min_rev = 0x0a108109; break;
case 0xa2010: min_rev = 0x0a20102e; break;
case 0xa2012: min_rev = 0x0a201211; break;
case 0xa4041: min_rev = 0x0a404108; break;
case 0xa5000: min_rev = 0x0a500012; break;
case 0xa6012: min_rev = 0x0a60120a; break;
case 0xa7041: min_rev = 0x0a704108; break;
case 0xa7052: min_rev = 0x0a705208; break;
case 0xa7080: min_rev = 0x0a708008; break;
case 0xa70c0: min_rev = 0x0a70c008; break;
case 0xaa002: min_rev = 0x0aa00216; break;
default:
pr_debug("%s: ucode_rev: 0x%x, current revision: 0x%x\n",
__func__, p.ucode_rev, c->microcode);
return false;
}
}
if (!min_rev)
return false;
return c->microcode >= min_rev;
}
static void tsa_init(struct cpuinfo_x86 *c)
{
if (cpu_has(c, X86_FEATURE_HYPERVISOR))
return;
if (c->x86 == 0x19) {
if (amd_check_tsa_microcode())
setup_force_cpu_cap(X86_FEATURE_VERW_CLEAR);
} else {
setup_force_cpu_cap(X86_FEATURE_TSA_SQ_NO);
setup_force_cpu_cap(X86_FEATURE_TSA_L1_NO);
}
}
static void bsp_init_amd(struct cpuinfo_x86 *c)
{
if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {
@ -687,6 +742,9 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
if (!(msr & MSR_K7_HWCR_SMMLOCK))
goto clear_sev;
tsa_init(c);
return;
clear_all:

121
arch/x86/kernel/cpu/bugs.c
View File

@ -49,6 +49,7 @@ static void __init l1d_flush_select_mitigation(void);
static void __init gds_select_mitigation(void);
static void __init srso_select_mitigation(void);
static void __init its_select_mitigation(void);
static void __init tsa_select_mitigation(void);
/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
@ -184,6 +185,7 @@ void __init cpu_select_mitigations(void)
srso_select_mitigation();
gds_select_mitigation();
its_select_mitigation();
tsa_select_mitigation();
}
/*
@ -2039,6 +2041,94 @@ static void update_mds_branch_idle(void)
#define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
#undef pr_fmt
#define pr_fmt(fmt) "Transient Scheduler Attacks: " fmt
enum tsa_mitigations {
TSA_MITIGATION_NONE,
TSA_MITIGATION_UCODE_NEEDED,
TSA_MITIGATION_USER_KERNEL,
TSA_MITIGATION_VM,
TSA_MITIGATION_FULL,
};
static const char * const tsa_strings[] = {
[TSA_MITIGATION_NONE] = "Vulnerable",
[TSA_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
[TSA_MITIGATION_USER_KERNEL] = "Mitigation: Clear CPU buffers: user/kernel boundary",
[TSA_MITIGATION_VM] = "Mitigation: Clear CPU buffers: VM",
[TSA_MITIGATION_FULL] = "Mitigation: Clear CPU buffers",
};
static enum tsa_mitigations tsa_mitigation __ro_after_init =
IS_ENABLED(CONFIG_MITIGATION_TSA) ? TSA_MITIGATION_FULL : TSA_MITIGATION_NONE;
static int __init tsa_parse_cmdline(char *str)
{
if (!str)
return -EINVAL;
if (!strcmp(str, "off"))
tsa_mitigation = TSA_MITIGATION_NONE;
else if (!strcmp(str, "on"))
tsa_mitigation = TSA_MITIGATION_FULL;
else if (!strcmp(str, "user"))
tsa_mitigation = TSA_MITIGATION_USER_KERNEL;
else if (!strcmp(str, "vm"))
tsa_mitigation = TSA_MITIGATION_VM;
else
pr_err("Ignoring unknown tsa=%s option.\n", str);
return 0;
}
early_param("tsa", tsa_parse_cmdline);
static void __init tsa_select_mitigation(void)
{
if (tsa_mitigation == TSA_MITIGATION_NONE)
return;
if (cpu_mitigations_off() || !boot_cpu_has_bug(X86_BUG_TSA)) {
tsa_mitigation = TSA_MITIGATION_NONE;
return;
}
if (!boot_cpu_has(X86_FEATURE_VERW_CLEAR))
tsa_mitigation = TSA_MITIGATION_UCODE_NEEDED;
switch (tsa_mitigation) {
case TSA_MITIGATION_USER_KERNEL:
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
break;
case TSA_MITIGATION_VM:
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
break;
case TSA_MITIGATION_UCODE_NEEDED:
if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
goto out;
pr_notice("Forcing mitigation on in a VM\n");
/*
* On the off-chance that microcode has been updated
* on the host, enable the mitigation in the guest just
* in case.
*/
fallthrough;
case TSA_MITIGATION_FULL:
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
break;
default:
break;
}
out:
pr_info("%s\n", tsa_strings[tsa_mitigation]);
}
void cpu_bugs_smt_update(void)
{
mutex_lock(&spec_ctrl_mutex);
@ -2092,6 +2182,24 @@ void cpu_bugs_smt_update(void)
break;
}
switch (tsa_mitigation) {
case TSA_MITIGATION_USER_KERNEL:
case TSA_MITIGATION_VM:
case TSA_MITIGATION_FULL:
case TSA_MITIGATION_UCODE_NEEDED:
/*
* TSA-SQ can potentially lead to info leakage between
* SMT threads.
*/
if (sched_smt_active())
static_branch_enable(&cpu_buf_idle_clear);
else
static_branch_disable(&cpu_buf_idle_clear);
break;
case TSA_MITIGATION_NONE:
break;
}
mutex_unlock(&spec_ctrl_mutex);
}
@ -3026,6 +3134,11 @@ static ssize_t srso_show_state(char *buf)
boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
}
static ssize_t tsa_show_state(char *buf)
{
return sysfs_emit(buf, "%s\n", tsa_strings[tsa_mitigation]);
}
static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
char *buf, unsigned int bug)
{
@ -3087,6 +3200,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
case X86_BUG_ITS:
return its_show_state(buf);
case X86_BUG_TSA:
return tsa_show_state(buf);
default:
break;
}
@ -3171,4 +3287,9 @@ ssize_t cpu_show_indirect_target_selection(struct device *dev, struct device_att
{
return cpu_show_common(dev, attr, buf, X86_BUG_ITS);
}
ssize_t cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *buf)
{
return cpu_show_common(dev, attr, buf, X86_BUG_TSA);
}
#endif

14
arch/x86/kernel/cpu/common.c
View File

@ -1146,6 +1146,8 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
#define ITS BIT(8)
/* CPU is affected by Indirect Target Selection, but guest-host isolation is not affected */
#define ITS_NATIVE_ONLY BIT(9)
/* CPU is affected by Transient Scheduler Attacks */
#define TSA BIT(10)
static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
@ -1193,7 +1195,7 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_AMD(0x16, RETBLEED),
VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO),
VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO),
VULNBL_AMD(0x19, SRSO),
VULNBL_AMD(0x19, SRSO | TSA),
{}
};
@ -1398,6 +1400,16 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
setup_force_cpu_bug(X86_BUG_ITS_NATIVE_ONLY);
}
if (c->x86_vendor == X86_VENDOR_AMD) {
if (!cpu_has(c, X86_FEATURE_TSA_SQ_NO) ||
!cpu_has(c, X86_FEATURE_TSA_L1_NO)) {
if (cpu_matches(cpu_vuln_blacklist, TSA) ||
/* Enable bug on Zen guests to allow for live migration. */
(cpu_has(c, X86_FEATURE_HYPERVISOR) && cpu_has(c, X86_FEATURE_ZEN)))
setup_force_cpu_bug(X86_BUG_TSA);
}
}
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;

2
arch/x86/kernel/cpu/scattered.c
View File

@ -44,6 +44,8 @@ static const struct cpuid_bit cpuid_bits[] = {
{ X86_FEATURE_CPB, CPUID_EDX, 9, 0x80000007, 0 },
{ X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 },
{ X86_FEATURE_MBA, CPUID_EBX, 6, 0x80000008, 0 },
{ X86_FEATURE_TSA_SQ_NO, CPUID_ECX, 1, 0x80000021, 0 },
{ X86_FEATURE_TSA_L1_NO, CPUID_ECX, 2, 0x80000021, 0 },
{ 0, 0, 0, 0, 0 }
};

6
arch/x86/kvm/svm/vmenter.S
View File

@ -77,6 +77,9 @@ SYM_FUNC_START(__svm_vcpu_run)
/* "POP" @vmcb to RAX. */
pop %_ASM_AX
/* Clobbers EFLAGS.ZF */
VM_CLEAR_CPU_BUFFERS
/* Enter guest mode */
sti
@ -190,6 +193,9 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
/* Move @vmcb to RAX. */
mov %_ASM_ARG1, %_ASM_AX
/* Clobbers EFLAGS.ZF */
VM_CLEAR_CPU_BUFFERS
/* Enter guest mode */
sti

7
drivers/base/cpu.c
View File

@ -601,6 +601,11 @@ ssize_t __weak cpu_show_indirect_target_selection(struct device *dev,
return sysfs_emit(buf, "Not affected\n");
}
ssize_t __weak cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *buf)
{
return sysfs_emit(buf, "Not affected\n");
}
static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
@ -616,6 +621,7 @@ static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL);
static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NULL);
static DEVICE_ATTR(reg_file_data_sampling, 0444, cpu_show_reg_file_data_sampling, NULL);
static DEVICE_ATTR(indirect_target_selection, 0444, cpu_show_indirect_target_selection, NULL);
static DEVICE_ATTR(tsa, 0444, cpu_show_tsa, NULL);
static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
@ -633,6 +639,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_spec_rstack_overflow.attr,
&dev_attr_reg_file_data_sampling.attr,
&dev_attr_indirect_target_selection.attr,
&dev_attr_tsa.attr,
NULL
};

1
include/linux/cpu.h
View File

@ -78,6 +78,7 @@ extern ssize_t cpu_show_reg_file_data_sampling(struct device *dev,
struct device_attribute *attr, char *buf);
extern ssize_t cpu_show_indirect_target_selection(struct device *dev,
struct device_attribute *attr, char *buf);
extern ssize_t cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *buf);
extern __printf(4, 5)
struct device *cpu_device_create(struct device *parent, void *drvdata,