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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen staging-4.7] x86/tsx: Implement controls for RTM force-abort mode
commit dcf96335d0e416e481c75eb3bc17f3fb80231b47
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Mar 18 17:08:25 2019 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue May 14 15:51:53 2019 +0100
x86/tsx: Implement controls for RTM force-abort mode
The CPUID bit and MSR are deliberately not exposed to guests, because they
won't exist on newer processors. As vPMU isn't security supported, the
misbehaviour of PCR3 isn't expected to impact production deployments.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
master commit: 6be613f29b4205349275d24367bd4c82fb2960dd
master date: 2019-03-12 17:05:21 +0000
---
docs/misc/xen-command-line.markdown | 17 ++++++++++++++++-
tools/misc/xen-cpuid.c | 6 +++++-
xen/arch/x86/cpu/intel.c | 3 +++
xen/arch/x86/cpu/vpmu.c | 9 +++++++++
xen/arch/x86/hvm/hvm.c | 4 ++++
xen/arch/x86/traps.c | 4 ++++
xen/include/asm-x86/cpufeature.h | 1 +
xen/include/asm-x86/msr-index.h | 3 +++
xen/include/asm-x86/vpmu.h | 1 +
xen/include/public/arch-x86/cpufeatureset.h | 1 +
10 files changed, 47 insertions(+), 2 deletions(-)
diff --git a/docs/misc/xen-command-line.markdown
b/docs/misc/xen-command-line.markdown
index 3855cd3391..b620768fb4 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1715,7 +1715,7 @@ Use Virtual Processor ID support if available. This
prevents the need for TLB
flushes on VM entry and exit, increasing performance.
### vpmu
-> `= ( <boolean> | { bts | ipc | arch [, ...] } )`
+> `= ( <boolean> | { bts | ipc | arch | rtm-abort=<bool> [, ...] } )`
> Default: `off`
@@ -1741,6 +1741,21 @@ in the Pre-Defined Architectural Performance Events
table from the Intel 64
and IA-32 Architectures Software Developer's Manual, Volume 3B, System
Programming Guide, Part 2.
+vpmu=rtm-abort controls a trade-off between working Restricted Transactional
+Memory, and working performance counters.
+
+All processors released to date (Q1 2019) supporting Transactional Memory
+Extensions suffer an erratum which has been addressed in microcode.
+
+Processors based on the Skylake microarchitecture with up-to-date
+microcode internally use performance counter 3 to work around the erratum.
+A consequence is that the counter gets reprogrammed whenever an `XBEGIN`
+instruction is executed.
+
+An alternative mode exists where PCR3 behaves as before, at the cost of
+`XBEGIN` unconditionally aborting. Enabling `rtm-abort` mode will
+activate this alternative mode.
+
If a boolean is not used, combinations of flags are allowed, comma separated.
For example, vpmu=arch,bts.
diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c
index 184f8ad136..288fc48831 100644
--- a/tools/misc/xen-cpuid.c
+++ b/tools/misc/xen-cpuid.c
@@ -149,7 +149,11 @@ static const char *str_e8b[32] =
static const char *str_7d0[32] =
{
- [0 ... 25] = "REZ",
+ [0 ... 11] = "REZ",
+
+ [12] = "REZ", [13] = "tsx-force-abort",
+
+ [14 ... 25] = "REZ",
[26] = "ibrsb", [27] = "stibp",
[28] = "l1d_flush", [29] = "arch_caps",
diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
index 181e815b39..62c14498a4 100644
--- a/xen/arch/x86/cpu/intel.c
+++ b/xen/arch/x86/cpu/intel.c
@@ -355,6 +355,9 @@ static void Intel_errata_workarounds(struct cpuinfo_x86 *c)
if (c->x86 == 6 && cpu_has_clflush &&
(c->x86_model == 29 || c->x86_model == 46 || c->x86_model == 47))
__set_bit(X86_FEATURE_CLFLUSH_MONITOR, c->x86_capability);
+
+ if (cpu_has_tsx_force_abort && opt_rtm_abort)
+ wrmsrl(MSR_TSX_FORCE_ABORT, TSX_FORCE_ABORT_RTM);
}
diff --git a/xen/arch/x86/cpu/vpmu.c b/xen/arch/x86/cpu/vpmu.c
index 2f9ddf656b..5635a9764d 100644
--- a/xen/arch/x86/cpu/vpmu.c
+++ b/xen/arch/x86/cpu/vpmu.c
@@ -53,6 +53,7 @@ CHECK_pmu_params;
static unsigned int __read_mostly opt_vpmu_enabled;
unsigned int __read_mostly vpmu_mode = XENPMU_MODE_OFF;
unsigned int __read_mostly vpmu_features = 0;
+bool_t __read_mostly opt_rtm_abort;
static void parse_vpmu_params(char *s);
custom_param("vpmu", parse_vpmu_params);
@@ -63,6 +64,8 @@ static DEFINE_PER_CPU(struct vcpu *, last_vcpu);
static int parse_vpmu_param(char *s, unsigned int len)
{
+ int val;
+
if ( !*s || !len )
return 0;
if ( !strncmp(s, "bts", len) )
@@ -71,6 +74,8 @@ static int parse_vpmu_param(char *s, unsigned int len)
vpmu_features |= XENPMU_FEATURE_IPC_ONLY;
else if ( !strncmp(s, "arch", len) )
vpmu_features |= XENPMU_FEATURE_ARCH_ONLY;
+ else if ( (val = parse_boolean("rtm-abort", s, s + len)) >= 0 )
+ opt_rtm_abort = val;
else
return 1;
return 0;
@@ -97,6 +102,10 @@ static void __init parse_vpmu_params(char *s)
break;
p = sep + 1;
}
+
+ if ( !vpmu_features ) /* rtm-abort doesn't imply vpmu=1 */
+ break;
+
/* fall through */
case 1:
/* Default VPMU mode */
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 522430b84c..ce2275667a 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3797,6 +3797,8 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t
*msr_content)
case MSR_PRED_CMD:
case MSR_FLUSH_CMD:
/* Write-only */
+ case MSR_TSX_FORCE_ABORT:
+ /* Not offered to guests. */
goto gp_fault;
case MSR_SPEC_CTRL:
@@ -4026,6 +4028,8 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t
msr_content,
case MSR_ARCH_CAPABILITIES:
/* Read-only */
+ case MSR_TSX_FORCE_ABORT:
+ /* Not offered to guests. */
goto gp_fault;
case MSR_AMD64_NB_CFG:
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 583936e9cb..4b257fb6a5 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2904,6 +2904,8 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
case MSR_INTEL_PLATFORM_INFO:
case MSR_ARCH_CAPABILITIES:
/* The MSR is read-only. */
+ case MSR_TSX_FORCE_ABORT:
+ /* Not offered to guests. */
goto fail;
case MSR_SPEC_CTRL:
@@ -3075,6 +3077,8 @@ static int emulate_privileged_op(struct cpu_user_regs
*regs)
case MSR_PRED_CMD:
case MSR_FLUSH_CMD:
/* Write-only */
+ case MSR_TSX_FORCE_ABORT:
+ /* Not offered to guests. */
goto fail;
case MSR_SPEC_CTRL:
diff --git a/xen/include/asm-x86/cpufeature.h b/xen/include/asm-x86/cpufeature.h
index f9c83352d4..c5001b4f28 100644
--- a/xen/include/asm-x86/cpufeature.h
+++ b/xen/include/asm-x86/cpufeature.h
@@ -85,6 +85,7 @@
#define cpu_has_avx boot_cpu_has(X86_FEATURE_AVX)
#define cpu_has_lwp boot_cpu_has(X86_FEATURE_LWP)
#define cpu_has_mpx boot_cpu_has(X86_FEATURE_MPX)
+#define cpu_has_tsx_force_abort boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)
#define cpu_has_arch_perfmon boot_cpu_has(X86_FEATURE_ARCH_PERFMON)
#define cpu_has_rdtscp boot_cpu_has(X86_FEATURE_RDTSCP)
#define cpu_has_svm boot_cpu_has(X86_FEATURE_SVM)
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index 76d92d8c65..c2aa36e9ef 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -50,6 +50,9 @@
#define MSR_FLUSH_CMD 0x0000010b
#define FLUSH_CMD_L1D (_AC(1, ULL) << 0)
+#define MSR_TSX_FORCE_ABORT 0x0000010f
+#define TSX_FORCE_ABORT_RTM (_AC(1, ULL) << 0)
+
/* 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/vpmu.h b/xen/include/asm-x86/vpmu.h
index 75b1973859..0072d12c89 100644
--- a/xen/include/asm-x86/vpmu.h
+++ b/xen/include/asm-x86/vpmu.h
@@ -127,6 +127,7 @@ static inline int vpmu_do_rdmsr(unsigned int msr, uint64_t
*msr_content)
extern unsigned int vpmu_mode;
extern unsigned int vpmu_features;
+extern bool_t opt_rtm_abort;
/* Context switch */
static inline void vpmu_switch_from(struct vcpu *prev)
diff --git a/xen/include/public/arch-x86/cpufeatureset.h
b/xen/include/public/arch-x86/cpufeatureset.h
index f5fb483556..73de8703d9 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -227,6 +227,7 @@ XEN_CPUFEATURE(CLZERO, 8*32+ 0) /*A CLZERO
instruction */
XEN_CPUFEATURE(IBPB, 8*32+12) /*A IBPB support only (no IBRS, used
by AMD) */
/* Intel-defined CPU features, CPUID level 0x00000007:0.edx, word 9 */
+XEN_CPUFEATURE(TSX_FORCE_ABORT, 9*32+13) /* MSR_TSX_FORCE_ABORT.RTM_ABORT */
XEN_CPUFEATURE(IBRSB, 9*32+26) /*A IBRS and IBPB support (used by
Intel) */
XEN_CPUFEATURE(STIBP, 9*32+27) /*A! STIBP */
XEN_CPUFEATURE(L1D_FLUSH, 9*32+28) /*S MSR_FLUSH_CMD and L1D flush. */
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.7
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