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arm64: KVM: Add support for Stage-2 control of memory types and cacheability

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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>
This commit is contained in:
Marc Zyngier
2018-04-06 12:27:28 +01:00
parent 1e4b044d22
commit e48d53a91f
9 changed files with 70 additions and 9 deletions
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20
arch/arm64/kernel/cpufeature.c
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@@ -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
{
/*