| Message ID | 20180612113643.32020-5-julien.grall@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | xen/arm: SSBD (aka Spectre-v4) mitigation (XSA-263) | expand |
On Tue, 12 Jun 2018, Julien Grall wrote: > As for Spectre variant-2, we rely on SMCCC 1.1 to provide the discovery > mechanism for detecting the SSBD mitigation. > > A new capability is also allocated for that purpose, and a config > option. > > This is part of XSA-263. > > Signed-off-by: Julien Grall <julien.grall@arm.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > Changes in v3: > - required should be false when then mitigation is not required > on a given CPU > > Changes in v2: > - Add the switch in this patch rather than the next one. > - s/supported/required/ > --- > xen/arch/arm/Kconfig | 10 +++++++ > xen/arch/arm/cpuerrata.c | 58 ++++++++++++++++++++++++++++++++++++++++ > xen/include/asm-arm/cpuerrata.h | 21 +++++++++++++++ > xen/include/asm-arm/cpufeature.h | 3 ++- > xen/include/asm-arm/smccc.h | 7 +++++ > 5 files changed, 98 insertions(+), 1 deletion(-) > > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig > index 8174c0c635..0e2d027060 100644 > --- a/xen/arch/arm/Kconfig > +++ b/xen/arch/arm/Kconfig > @@ -73,6 +73,16 @@ config SBSA_VUART_CONSOLE > Allows a guest to use SBSA Generic UART as a console. The > SBSA Generic UART implements a subset of ARM PL011 UART. > > +config ARM_SSBD > + bool "Speculative Store Bypass Disable" if EXPERT = "y" > + depends on HAS_ALTERNATIVE > + default y > + help > + This enables mitigation of bypassing of previous stores by speculative > + loads. > + > + If unsure, say Y. > + > endmenu > > menu "ARM errata workaround via the alternative framework" > diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c > index 1baa20654b..1a6130406c 100644 > --- a/xen/arch/arm/cpuerrata.c > +++ b/xen/arch/arm/cpuerrata.c > @@ -235,6 +235,58 @@ static int enable_ic_inv_hardening(void *data) > > #endif > > +#ifdef CONFIG_ARM_SSBD > + > +/* > + * Assembly code may use the variable directly, so we need to make sure > + * it fits in a register. > + */ > +DEFINE_PER_CPU_READ_MOSTLY(register_t, ssbd_callback_required); > + > +static bool has_ssbd_mitigation(const struct arm_cpu_capabilities *entry) > +{ > + struct arm_smccc_res res; > + bool required; > + > + if ( smccc_ver < SMCCC_VERSION(1, 1) ) > + return false; > + > + /* > + * The probe function return value is either negative (unsupported > + * or mitigated), positive (unaffected), or zero (requires > + * mitigation). We only need to do anything in the last case. > + */ > + arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FID, > + ARM_SMCCC_ARCH_WORKAROUND_2_FID, &res); > + > + switch ( (int)res.a0 ) > + { > + case ARM_SMCCC_NOT_SUPPORTED: > + return false; > + > + case ARM_SMCCC_NOT_REQUIRED: > + return false; > + > + case ARM_SMCCC_SUCCESS: > + required = true; > + break; > + > + case 1: /* Mitigation not required on this CPU. */ > + required = false; > + break; > + > + default: > + ASSERT_UNREACHABLE(); > + return false; > + } > + > + if ( required ) > + this_cpu(ssbd_callback_required) = 1; > + > + return required; > +} > +#endif > + > #define MIDR_RANGE(model, min, max) \ > .matches = is_affected_midr_range, \ > .midr_model = model, \ > @@ -336,6 +388,12 @@ static const struct arm_cpu_capabilities arm_errata[] = { > .enable = enable_ic_inv_hardening, > }, > #endif > +#ifdef CONFIG_ARM_SSBD > + { > + .capability = ARM_SSBD, > + .matches = has_ssbd_mitigation, > + }, > +#endif > {}, > }; > > diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h > index 4e45b237c8..e628d3ff56 100644 > --- a/xen/include/asm-arm/cpuerrata.h > +++ b/xen/include/asm-arm/cpuerrata.h > @@ -27,9 +27,30 @@ static inline bool check_workaround_##erratum(void) \ > > CHECK_WORKAROUND_HELPER(766422, ARM32_WORKAROUND_766422, CONFIG_ARM_32) > CHECK_WORKAROUND_HELPER(834220, ARM64_WORKAROUND_834220, CONFIG_ARM_64) > +CHECK_WORKAROUND_HELPER(ssbd, ARM_SSBD, CONFIG_ARM_SSBD) > > #undef CHECK_WORKAROUND_HELPER > > +#ifdef CONFIG_ARM_SSBD > + > +#include <asm/current.h> > + > +DECLARE_PER_CPU(register_t, ssbd_callback_required); > + > +static inline bool cpu_require_ssbd_mitigation(void) > +{ > + return this_cpu(ssbd_callback_required); > +} > + > +#else > + > +static inline bool cpu_require_ssbd_mitigation(void) > +{ > + return false; > +} > + > +#endif > + > #endif /* __ARM_CPUERRATA_H__ */ > /* > * Local variables: > diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h > index e557a095af..2a5c075d3b 100644 > --- a/xen/include/asm-arm/cpufeature.h > +++ b/xen/include/asm-arm/cpufeature.h > @@ -43,8 +43,9 @@ > #define SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT 5 > #define SKIP_CTXT_SWITCH_SERROR_SYNC 6 > #define ARM_HARDEN_BRANCH_PREDICTOR 7 > +#define ARM_SSBD 8 > > -#define ARM_NCAPS 8 > +#define ARM_NCAPS 9 > > #ifndef __ASSEMBLY__ > > diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h > index 8342cc33fe..a6804cec99 100644 > --- a/xen/include/asm-arm/smccc.h > +++ b/xen/include/asm-arm/smccc.h > @@ -258,7 +258,14 @@ struct arm_smccc_res { > ARM_SMCCC_OWNER_ARCH, \ > 0x8000) > > +#define ARM_SMCCC_ARCH_WORKAROUND_2_FID \ > + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ > + ARM_SMCCC_CONV_32, \ > + ARM_SMCCC_OWNER_ARCH, \ > + 0x7FFF) > + > /* SMCCC error codes */ > +#define ARM_SMCCC_NOT_REQUIRED (-2) > #define ARM_SMCCC_ERR_UNKNOWN_FUNCTION (-1) > #define ARM_SMCCC_NOT_SUPPORTED (-1) > #define ARM_SMCCC_SUCCESS (0) > -- > 2.11.0 >
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig index 8174c0c635..0e2d027060 100644 --- a/xen/arch/arm/Kconfig +++ b/xen/arch/arm/Kconfig @@ -73,6 +73,16 @@ config SBSA_VUART_CONSOLE Allows a guest to use SBSA Generic UART as a console. The SBSA Generic UART implements a subset of ARM PL011 UART. +config ARM_SSBD + bool "Speculative Store Bypass Disable" if EXPERT = "y" + depends on HAS_ALTERNATIVE + default y + help + This enables mitigation of bypassing of previous stores by speculative + loads. + + If unsure, say Y. + endmenu menu "ARM errata workaround via the alternative framework" diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c index 1baa20654b..1a6130406c 100644 --- a/xen/arch/arm/cpuerrata.c +++ b/xen/arch/arm/cpuerrata.c @@ -235,6 +235,58 @@ static int enable_ic_inv_hardening(void *data) #endif +#ifdef CONFIG_ARM_SSBD + +/* + * Assembly code may use the variable directly, so we need to make sure + * it fits in a register. + */ +DEFINE_PER_CPU_READ_MOSTLY(register_t, ssbd_callback_required); + +static bool has_ssbd_mitigation(const struct arm_cpu_capabilities *entry) +{ + struct arm_smccc_res res; + bool required; + + if ( smccc_ver < SMCCC_VERSION(1, 1) ) + return false; + + /* + * The probe function return value is either negative (unsupported + * or mitigated), positive (unaffected), or zero (requires + * mitigation). We only need to do anything in the last case. + */ + arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FID, + ARM_SMCCC_ARCH_WORKAROUND_2_FID, &res); + + switch ( (int)res.a0 ) + { + case ARM_SMCCC_NOT_SUPPORTED: + return false; + + case ARM_SMCCC_NOT_REQUIRED: + return false; + + case ARM_SMCCC_SUCCESS: + required = true; + break; + + case 1: /* Mitigation not required on this CPU. */ + required = false; + break; + + default: + ASSERT_UNREACHABLE(); + return false; + } + + if ( required ) + this_cpu(ssbd_callback_required) = 1; + + return required; +} +#endif + #define MIDR_RANGE(model, min, max) \ .matches = is_affected_midr_range, \ .midr_model = model, \ @@ -336,6 +388,12 @@ static const struct arm_cpu_capabilities arm_errata[] = { .enable = enable_ic_inv_hardening, }, #endif +#ifdef CONFIG_ARM_SSBD + { + .capability = ARM_SSBD, + .matches = has_ssbd_mitigation, + }, +#endif {}, }; diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h index 4e45b237c8..e628d3ff56 100644 --- a/xen/include/asm-arm/cpuerrata.h +++ b/xen/include/asm-arm/cpuerrata.h @@ -27,9 +27,30 @@ static inline bool check_workaround_##erratum(void) \ CHECK_WORKAROUND_HELPER(766422, ARM32_WORKAROUND_766422, CONFIG_ARM_32) CHECK_WORKAROUND_HELPER(834220, ARM64_WORKAROUND_834220, CONFIG_ARM_64) +CHECK_WORKAROUND_HELPER(ssbd, ARM_SSBD, CONFIG_ARM_SSBD) #undef CHECK_WORKAROUND_HELPER +#ifdef CONFIG_ARM_SSBD + +#include <asm/current.h> + +DECLARE_PER_CPU(register_t, ssbd_callback_required); + +static inline bool cpu_require_ssbd_mitigation(void) +{ + return this_cpu(ssbd_callback_required); +} + +#else + +static inline bool cpu_require_ssbd_mitigation(void) +{ + return false; +} + +#endif + #endif /* __ARM_CPUERRATA_H__ */ /* * Local variables: diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h index e557a095af..2a5c075d3b 100644 --- a/xen/include/asm-arm/cpufeature.h +++ b/xen/include/asm-arm/cpufeature.h @@ -43,8 +43,9 @@ #define SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT 5 #define SKIP_CTXT_SWITCH_SERROR_SYNC 6 #define ARM_HARDEN_BRANCH_PREDICTOR 7 +#define ARM_SSBD 8 -#define ARM_NCAPS 8 +#define ARM_NCAPS 9 #ifndef __ASSEMBLY__ diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h index 8342cc33fe..a6804cec99 100644 --- a/xen/include/asm-arm/smccc.h +++ b/xen/include/asm-arm/smccc.h @@ -258,7 +258,14 @@ struct arm_smccc_res { ARM_SMCCC_OWNER_ARCH, \ 0x8000) +#define ARM_SMCCC_ARCH_WORKAROUND_2_FID \ + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ + ARM_SMCCC_CONV_32, \ + ARM_SMCCC_OWNER_ARCH, \ + 0x7FFF) + /* SMCCC error codes */ +#define ARM_SMCCC_NOT_REQUIRED (-2) #define ARM_SMCCC_ERR_UNKNOWN_FUNCTION (-1) #define ARM_SMCCC_NOT_SUPPORTED (-1) #define ARM_SMCCC_SUCCESS (0)
As for Spectre variant-2, we rely on SMCCC 1.1 to provide the discovery mechanism for detecting the SSBD mitigation. A new capability is also allocated for that purpose, and a config option. This is part of XSA-263. Signed-off-by: Julien Grall <julien.grall@arm.com> --- Changes in v3: - required should be false when then mitigation is not required on a given CPU Changes in v2: - Add the switch in this patch rather than the next one. - s/supported/required/ --- xen/arch/arm/Kconfig | 10 +++++++ xen/arch/arm/cpuerrata.c | 58 ++++++++++++++++++++++++++++++++++++++++ xen/include/asm-arm/cpuerrata.h | 21 +++++++++++++++ xen/include/asm-arm/cpufeature.h | 3 ++- xen/include/asm-arm/smccc.h | 7 +++++ 5 files changed, 98 insertions(+), 1 deletion(-)