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arm64/sve: Detect SVE and activate runtime support 

This patch enables detection of hardware SVE support via the
cpufeatures framework, and reports its presence to the kernel and
userspace via the new ARM64_SVE cpucap and HWCAP_SVE hwcap
respectively.

Userspace can also detect SVE using ID_AA64PFR0_EL1, using the
cpufeatures MRS emulation.

When running on hardware that supports SVE, this enables runtime
kernel support for SVE, and allows user tasks to execute SVE
instructions and make of the of the SVE-specific user/kernel
interface extensions implemented by this series.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Dave Martin 2017-10-31 15:51:19 +00:00 committed by Will Deacon
parent 07d79fe7c2
commit 43994d824e
8 changed files with 36 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/arm64/cpu-feature-registers.txt
View File

@ -142,7 +142,11 @@ infrastructure:
x--------------------------------------------------x
| Name | bits | visible |
|--------------------------------------------------|
| RES0 | [63-28] | n |
| RES0 | [63-36] | n |
|--------------------------------------------------|
| SVE | [35-32] | y |
|--------------------------------------------------|
| RES0 | [31-28] | n |
|--------------------------------------------------|
| GIC | [27-24] | n |
|--------------------------------------------------|

4
Documentation/arm64/elf_hwcaps.txt
View File

@ -154,3 +154,7 @@ HWCAP_ASIMDDP
HWCAP_SHA512
Functionality implied by ID_AA64ISAR0_EL1.SHA2 == 0b0002.
HWCAP_SVE
Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001.

3
arch/arm64/include/asm/cpucaps.h
View File

@ -40,7 +40,8 @@
#define ARM64_WORKAROUND_858921 19
#define ARM64_WORKAROUND_CAVIUM_30115 20
#define ARM64_HAS_DCPOP 21
#define ARM64_SVE 22
#define ARM64_NCAPS 22
#define ARM64_NCAPS 23
#endif /* __ASM_CPUCAPS_H */

3
arch/arm64/include/asm/cpufeature.h
View File

@ -273,7 +273,8 @@ static inline bool system_uses_ttbr0_pan(void)
static inline bool system_supports_sve(void)
{
return false;
return IS_ENABLED(CONFIG_ARM64_SVE) &&
cpus_have_const_cap(ARM64_SVE);
}
/*

1
arch/arm64/include/uapi/asm/hwcap.h
View File

@ -41,5 +41,6 @@
#define HWCAP_SM4 (1 << 19)
#define HWCAP_ASIMDDP (1 << 20)
#define HWCAP_SHA512 (1 << 21)
#define HWCAP_SVE (1 << 22)
#endif /* _UAPI__ASM_HWCAP_H */

17
arch/arm64/kernel/cpufeature.c
View File

@ -145,6 +145,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
};
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_GIC_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_FP_SHIFT, 4, ID_AA64PFR0_FP_NI),
@ -948,6 +949,19 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.min_field_value = 1,
},
#endif
#ifdef CONFIG_ARM64_SVE
{
.desc = "Scalable Vector Extension",
.capability = ARM64_SVE,
.def_scope = SCOPE_SYSTEM,
.sys_reg = SYS_ID_AA64PFR0_EL1,
.sign = FTR_UNSIGNED,
.field_pos = ID_AA64PFR0_SVE_SHIFT,
.min_field_value = ID_AA64PFR0_SVE,
.matches = has_cpuid_feature,
.enable = sve_kernel_enable,
},
#endif /* CONFIG_ARM64_SVE */
{},
};
@ -985,6 +999,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_JSCVT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_JSCVT),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_FCMA_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_FCMA),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_LRCPC),
#ifdef CONFIG_ARM64_SVE
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_SVE_SHIFT, FTR_UNSIGNED, ID_AA64PFR0_SVE, CAP_HWCAP, HWCAP_SVE),
#endif
{},
};

1
arch/arm64/kernel/cpuinfo.c
View File

@ -75,6 +75,7 @@ static const char *const hwcap_str[] = {
"sm4",
"asimddp",
"sha512",
"sve",
NULL
};

7
arch/arm64/kernel/entry.S
View File

@ -867,9 +867,10 @@ el0_svc:
mov wscno, w8 // syscall number in w8
mov wsc_nr, #__NR_syscalls
#ifndef CONFIG_ARM64_SVE
#ifdef CONFIG_ARM64_SVE
alternative_if_not ARM64_SVE
b el0_svc_naked
#else
alternative_else_nop_endif
tbz x16, #TIF_SVE, el0_svc_naked // Skip unless TIF_SVE set:
bic x16, x16, #_TIF_SVE // discard SVE state
str x16, [tsk, #TSK_TI_FLAGS]
@ -884,7 +885,7 @@ el0_svc:
mrs x9, cpacr_el1
bic x9, x9, #CPACR_EL1_ZEN_EL0EN // disable SVE for el0
msr cpacr_el1, x9 // synchronised by eret to el0
#endif /* CONFIG_ARM64_SVE */
#endif
el0_svc_naked: // compat entry point
stp x0, xscno, [sp, #S_ORIG_X0] // save the original x0 and syscall number