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| author | Marc Zyngier <marc.zyngier@arm.com> | 2018-04-06 13:27:28 +0200 |
|---|---|---|
| committer | Marc Zyngier <marc.zyngier@arm.com> | 2018-07-09 12:37:41 +0200 |
| commit | e48d53a91f6e90873e21a5ca5e8c0d7a9f8936a4 (patch) | |
| tree | 8226aa3bd5ae8eefb39ad90d66fff26917bd747b /arch/arm64/kernel/cpufeature.c | |
| parent | Linux 4.18-rc4 (diff) | |
| download | linux-e48d53a91f6e90873e21a5ca5e8c0d7a9f8936a4.tar.xz linux-e48d53a91f6e90873e21a5ca5e8c0d7a9f8936a4.zip | |
arm64: KVM: Add support for Stage-2 control of memory types and cacheability
Up to ARMv8.3, the combinaison of Stage-1 and Stage-2 attributes
results in the strongest attribute of the two stages. This means
that the hypervisor has to perform quite a lot of cache maintenance
just in case the guest has some non-cacheable mappings around.
ARMv8.4 solves this problem by offering a different mode (FWB) where
Stage-2 has total control over the memory attribute (this is limited
to systems where both I/O and instruction fetches are coherent with
the dcache). This is achieved by having a different set of memory
attributes in the page tables, and a new bit set in HCR_EL2.
On such a system, we can then safely sidestep any form of dcache
management.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'arch/arm64/kernel/cpufeature.c')
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index f24892a40d2c..d58d1f0abe16 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -192,6 +192,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr1[] = { }; static const struct arm64_ftr_bits ftr_id_aa64mmfr2[] = { + ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_FWB_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_AT_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_LVA_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_IESB_SHIFT, 4, 0), @@ -1026,6 +1027,14 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused) } #endif +static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused) +{ + u64 val = read_sysreg_s(SYS_CLIDR_EL1); + + /* Check that CLIDR_EL1.LOU{U,IS} are both 0 */ + WARN_ON(val & (7 << 27 | 7 << 21)); +} + static const struct arm64_cpu_capabilities arm64_features[] = { { .desc = "GIC system register CPU interface", @@ -1182,6 +1191,17 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .type = ARM64_CPUCAP_SYSTEM_FEATURE, .matches = has_cache_dic, }, + { + .desc = "Stage-2 Force Write-Back", + .type = ARM64_CPUCAP_SYSTEM_FEATURE, + .capability = ARM64_HAS_STAGE2_FWB, + .sys_reg = SYS_ID_AA64MMFR2_EL1, + .sign = FTR_UNSIGNED, + .field_pos = ID_AA64MMFR2_FWB_SHIFT, + .min_field_value = 1, + .matches = has_cpuid_feature, + .cpu_enable = cpu_has_fwb, + }, #ifdef CONFIG_ARM64_HW_AFDBM { /* |