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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.8] x86/tsx: Introduce tsx= to use MSR_TSX_CTRL when available
commit a70ba89abbeb72e1bfd7496eb853fad3058c881d
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Jun 19 18:16:03 2019 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Nov 12 17:17:58 2019 +0000
x86/tsx: Introduce tsx= to use MSR_TSX_CTRL when available
To protect against the TSX Async Abort speculative vulnerability, Intel have
released new microcode for affected parts which introduce the MSR_TSX_CTRL
control, which allows TSX to be turned off. This will be architectural on
future parts.
Introduce tsx= to provide a global on/off for TSX, including its enumeration
via CPUID. Provide stub virtualisation of this MSR, as it is not exposed to
guests at the moment.
VMs may have booted before microcode is loaded, or before hosts have
rebooted,
and they still want to migrate freely. A VM which booted seeing TSX can
migrate safely to hosts with TSX disabled - TSX will start unconditionally
aborting, but still behave in a manner compatible with the ABI.
The guest-visible behaviour is equivalent to late loading the microcode and
setting the RTM_DISABLE bit in the course of live patching.
This is part of XSA-305 / CVE-2019-11135
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
docs/misc/xen-command-line.markdown | 14 +++++++
xen/arch/x86/Makefile | 1 +
xen/arch/x86/hvm/hvm.c | 21 +++++++++--
xen/arch/x86/setup.c | 2 +
xen/arch/x86/smpboot.c | 2 +
xen/arch/x86/traps.c | 21 +++++++++--
xen/arch/x86/tsx.c | 74 +++++++++++++++++++++++++++++++++++++
xen/include/asm-x86/msr-index.h | 5 +++
xen/include/asm-x86/processor.h | 13 +++++++
xen/include/xen/lib.h | 10 +++++
10 files changed, 157 insertions(+), 6 deletions(-)
diff --git a/docs/misc/xen-command-line.markdown
b/docs/misc/xen-command-line.markdown
index 7f60ddbbc6..28fcceb6fc 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1727,6 +1727,20 @@ pages) must also be specified via the tbuf\_size
parameter.
### tsc
> `= unstable | skewed | stable:socket`
+### tsx
+ = <bool>
+
+ Applicability: x86
+ Default: true
+
+Controls for the use of Transactional Synchronization eXtensions.
+
+On Intel parts released in Q3 2019 (with updated microcode), and future parts,
+a control has been introduced which allows TSX to be turned off.
+
+On systems with the ability to turn TSX off, this boolean offers system wide
+control of whether TSX is enabled or disabled.
+
### ucode
> `= [<integer> | scan]`
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index fc90449ea3..09e7a1096d 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -62,6 +62,7 @@ obj-y += sysctl.o
obj-y += time.o
obj-y += trace.o
obj-y += traps.o
+obj-y += tsx.o
obj-y += usercopy.o
obj-y += x86_emulate.o
obj-$(CONFIG_TBOOT) += tboot.o
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 5338d20c41..85350b33aa 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3600,9 +3600,22 @@ void hvm_cpuid(unsigned int input, unsigned int *eax,
unsigned int *ebx,
case 0x7:
if ( count == 0 )
{
- /* Fold host's FDP_EXCP_ONLY and NO_FPU_SEL into guest's view. */
- *ebx &= (hvm_featureset[FEATURESET_7b0] &
- ~special_features[FEATURESET_7b0]);
+ /*
+ * Fold host's FDP_EXCP_ONLY and NO_FPU_SEL into guest's view.
+ *
+ * On hardware with MSR_TSX_CTRL, the admin may have elected to
+ * disable TSX and hide the feature bits. Migrating-in VMs may
+ * have been booted pre-mitigation when the TSX features were
+ * visbile.
+ *
+ * This situation is compatible (albeit with a perf hit to any TSX
+ * code in the guest), so allow the feature bits to remain set.
+ */
+ *ebx &= ((hvm_featureset[FEATURESET_7b0] &
+ ~special_features[FEATURESET_7b0]) |
+ (cpu_has_tsx_ctrl ?
+ (cpufeat_mask(X86_FEATURE_HLE) |
+ cpufeat_mask(X86_FEATURE_RTM)) : 0));
*ebx |= (host_featureset[FEATURESET_7b0] &
special_features[FEATURESET_7b0]);
@@ -3955,6 +3968,7 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t
*msr_content)
case MSR_FLUSH_CMD:
/* Write-only */
case MSR_TSX_FORCE_ABORT:
+ case MSR_TSX_CTRL:
/* Not offered to guests. */
goto gp_fault;
@@ -4201,6 +4215,7 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t
msr_content,
case MSR_ARCH_CAPABILITIES:
/* Read-only */
case MSR_TSX_FORCE_ABORT:
+ case MSR_TSX_CTRL:
/* Not offered to guests. */
goto gp_fault;
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 3a7b36251c..a3fb9251b5 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1484,6 +1484,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
early_microcode_init();
+ tsx_init(); /* Needs microcode. May change HLE/RTM feature bits. */
+
identify_cpu(&boot_cpu_data);
set_in_cr4(X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT);
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 4c602491ba..4a3e080f78 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -361,6 +361,8 @@ void start_secondary(void *unused)
if ( boot_cpu_has(X86_FEATURE_IBRSB) )
wrmsrl(MSR_SPEC_CTRL, default_xen_spec_ctrl);
+ tsx_init(); /* Needs microcode. May change HLE/RTM feature bits. */
+
smp_callin();
init_percpu_time();
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 3c1c4e2c2d..2d5dbcaa3a 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1141,9 +1141,22 @@ void pv_cpuid(uint32_t leaf, uint32_t subleaf,
case 0x00000007:
if ( subleaf == 0 )
{
- /* Fold host's FDP_EXCP_ONLY and NO_FPU_SEL into guest's view. */
- b &= (pv_featureset[FEATURESET_7b0] &
- ~special_features[FEATURESET_7b0]);
+ /*
+ * Fold host's FDP_EXCP_ONLY and NO_FPU_SEL into guest's view.
+ *
+ * On hardware with MSR_TSX_CTRL, the admin may have elected to
+ * disable TSX and hide the feature bits. Migrating-in VMs may
+ * have been booted pre-mitigation when the TSX features were
+ * visbile.
+ *
+ * This situation is compatible (albeit with a perf hit to any TSX
+ * code in the guest), so allow the feature bits to remain set.
+ */
+ b &= ((pv_featureset[FEATURESET_7b0] &
+ ~special_features[FEATURESET_7b0]) |
+ (cpu_has_tsx_ctrl ?
+ (cpufeat_mask(X86_FEATURE_HLE) |
+ cpufeat_mask(X86_FEATURE_RTM)) : 0));
b |= (host_featureset[FEATURESET_7b0] &
special_features[FEATURESET_7b0]);
@@ -2531,6 +2544,7 @@ static int priv_op_read_msr(unsigned int reg, uint64_t
*val,
case MSR_FLUSH_CMD:
/* Write-only */
case MSR_TSX_FORCE_ABORT:
+ case MSR_TSX_CTRL:
/* Not offered to guests. */
break;
@@ -2762,6 +2776,7 @@ static int priv_op_write_msr(unsigned int reg, uint64_t
val,
case MSR_ARCH_CAPABILITIES:
/* The MSR is read-only. */
case MSR_TSX_FORCE_ABORT:
+ case MSR_TSX_CTRL:
/* Not offered to guests. */
break;
diff --git a/xen/arch/x86/tsx.c b/xen/arch/x86/tsx.c
new file mode 100644
index 0000000000..3a853d38f6
--- /dev/null
+++ b/xen/arch/x86/tsx.c
@@ -0,0 +1,74 @@
+#include <xen/init.h>
+#include <asm/msr.h>
+
+/*
+ * Valid values:
+ * 1 => Explicit tsx=1
+ * 0 => Explicit tsx=0
+ * -1 => Default, implicit tsx=1
+ *
+ * This is arranged such that the bottom bit encodes whether TSX is actually
+ * disabled, while identifying various explicit (>=0) and implicit (<0)
+ * conditions.
+ */
+int8_t __read_mostly opt_tsx = -1;
+int8_t __read_mostly cpu_has_tsx_ctrl = -1;
+
+static int __init parse_tsx(const char *s)
+{
+ int rc = 0, val = parse_bool(s);
+
+ if ( val >= 0 )
+ opt_tsx = val;
+ else
+ rc = -EINVAL;
+
+ return rc;
+}
+custom_param("tsx", parse_tsx);
+
+void tsx_init(void)
+{
+ /*
+ * This function is first called between microcode being loaded, and CPUID
+ * being scanned generally. Calculate from raw data whether MSR_TSX_CTRL
+ * is available.
+ */
+ if ( unlikely(cpu_has_tsx_ctrl < 0) )
+ {
+ uint64_t caps = 0;
+
+ if ( boot_cpu_data.cpuid_level >= 7 &&
+ (cpuid_count_edx(7, 0) & cpufeat_mask(X86_FEATURE_ARCH_CAPS)) )
+ rdmsrl(MSR_ARCH_CAPABILITIES, caps);
+
+ cpu_has_tsx_ctrl = !!(caps & ARCH_CAPS_TSX_CTRL);
+ }
+
+ if ( cpu_has_tsx_ctrl )
+ {
+ uint64_t val;
+
+ rdmsrl(MSR_TSX_CTRL, val);
+
+ val &= ~(TSX_CTRL_RTM_DISABLE | TSX_CTRL_CPUID_CLEAR);
+ /* Check bottom bit only. Higher bits are various sentinals. */
+ if ( !(opt_tsx & 1) )
+ val |= TSX_CTRL_RTM_DISABLE | TSX_CTRL_CPUID_CLEAR;
+
+ wrmsrl(MSR_TSX_CTRL, val);
+ }
+ else if ( opt_tsx >= 0 )
+ printk_once(XENLOG_WARNING
+ "MSR_TSX_CTRL not available - Ignoring tsx= setting\n");
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index 0a596f7489..1982137a33 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -55,6 +55,7 @@
#define ARCH_CAPS_SSB_NO (_AC(1, ULL) << 4)
#define ARCH_CAPS_MDS_NO (_AC(1, ULL) << 5)
#define ARCH_CAPS_IF_PSCHANGE_MC_NO (_AC(1, ULL) << 6)
+#define ARCH_CAPS_TSX_CTRL (_AC(1, ULL) << 7)
#define MSR_FLUSH_CMD 0x0000010b
#define FLUSH_CMD_L1D (_AC(1, ULL) << 0)
@@ -62,6 +63,10 @@
#define MSR_TSX_FORCE_ABORT 0x0000010f
#define TSX_FORCE_ABORT_RTM (_AC(1, ULL) << 0)
+#define MSR_TSX_CTRL 0x00000122
+#define TSX_CTRL_RTM_DISABLE (_AC(1, ULL) << 0)
+#define TSX_CTRL_CPUID_CLEAR (_AC(1, ULL) << 1)
+
/* Intel MSRs. Some also available on other CPUs */
#define MSR_IA32_PERFCTR0 0x000000c1
#define MSR_IA32_A_PERFCTR0 0x000004c1
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index a5319e3aaf..dc3f4f8490 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -339,6 +339,16 @@ static always_inline unsigned int cpuid_edx(unsigned int
op)
return edx;
}
+static always_inline unsigned int cpuid_count_edx(
+ unsigned int leaf, unsigned int subleaf)
+{
+ unsigned int edx, tmp;
+
+ cpuid_count(leaf, subleaf, &tmp, &tmp, &tmp, &edx);
+
+ return edx;
+}
+
static inline unsigned long read_cr0(void)
{
unsigned long cr0;
@@ -692,6 +702,9 @@ static inline void pv_cpuid_regs(struct cpu_user_regs *regs)
®s->_eax, ®s->_ebx, ®s->_ecx, ®s->_edx);
}
+extern int8_t opt_tsx, cpu_has_tsx_ctrl;
+void tsx_init(void);
+
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_X86_PROCESSOR_H */
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index b9d1c87ffd..b9d2ef0c79 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -103,6 +103,16 @@ extern int printk_ratelimit(void);
#define gprintk(lvl, fmt, args...) \
printk(XENLOG_GUEST lvl "%pv " fmt, current, ## args)
+#define printk_once(fmt, args...) \
+({ \
+ static bool __read_mostly once_; \
+ if ( unlikely(!once_) ) \
+ { \
+ once_ = true; \
+ printk(fmt, ## args); \
+ } \
+})
+
#ifdef NDEBUG
static inline void
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8
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