arm64: KVM: Runtime detection of lower HYP offset

Add the code that enables the switch to the lower HYP VA range.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 811773d1c1d015ca8e47239f5375d3ced3c04b48..ffb3e14dda60dd0c86ce80b3378fe0d08c8bd143 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -726,6 +726,19 @@ static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused
        return is_kernel_in_hyp_mode();
 }
 
+static bool hyp_offset_low(const struct arm64_cpu_capabilities *entry,
+                          int __unused)
+{
+       phys_addr_t idmap_addr = virt_to_phys(__hyp_idmap_text_start);
+
+       /*
+        * Activate the lower HYP offset only if:
+        * - the idmap doesn't clash with it,
+        * - the kernel is not running at EL2.
+        */
+       return idmap_addr > GENMASK(VA_BITS - 2, 0) && !is_kernel_in_hyp_mode();
+}
+
 static const struct arm64_cpu_capabilities arm64_features[] = {
        {
                .desc = "GIC system register CPU interface",
@@ -803,6 +816,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
                .field_pos = ID_AA64PFR0_EL0_SHIFT,
                .min_field_value = ID_AA64PFR0_EL0_32BIT_64BIT,
        },
+       {
+               .desc = "Reduced HYP mapping offset",
+               .capability = ARM64_HYP_OFFSET_LOW,
+               .def_scope = SCOPE_SYSTEM,
+               .matches = hyp_offset_low,
+       },
        {},
 };