[PATCH 01/26] KVM: arm64: Check advertised Stage-2 page size capability

Marc Zyngier
2020-04-22T12:01:07Z

With ARMv8.5-GTG, the hardware (or more likely a hypervisor) can
advertise the supported Stage-2 page sizes.

Let's check this at boot time.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_host.h | 2 +-
arch/arm64/include/asm/sysreg.h | 3 +++
arch/arm64/kernel/cpufeature.c | 8 +++++++
arch/arm64/kvm/reset.c | 40 ++++++++++++++++++++++++++++---
virt/kvm/arm/arm.c | 4 +---
5 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 32c8a675e5a4a..7dd8fefa6aecd 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -670,7 +670,7 @@ static inline int kvm_arm_have_ssbd(void)
void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);

-void kvm_set_ipa_limit(void);
+int kvm_set_ipa_limit(void);

#define __KVM_HAVE_ARCH_VM_ALLOC
struct kvm *kvm_arch_alloc_vm(void);
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index ebc6224328318..5d10c9148e844 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -686,6 +686,9 @@
#define ID_AA64ZFR0_SVEVER_SVE2 0x1

/* id_aa64mmfr0 */
+#define ID_AA64MMFR0_TGRAN4_2_SHIFT 40
+#define ID_AA64MMFR0_TGRAN64_2_SHIFT 36
+#define ID_AA64MMFR0_TGRAN16_2_SHIFT 32
#define ID_AA64MMFR0_TGRAN4_SHIFT 28
#define ID_AA64MMFR0_TGRAN64_SHIFT 24
#define ID_AA64MMFR0_TGRAN16_SHIFT 20
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9fac745aa7bb2..9892a845d06c9 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -208,6 +208,14 @@ static const struct arm64_ftr_bits ftr_id_aa64zfr0[] = {
};

static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
+ /*
+ * Page size not being supported at Stage-2 are not fatal. You
+ * just give up KVM if PAGE_SIZE isn't supported there. Go fix
+ * your favourite nesting hypervisor.
+ */
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64MMFR0_TGRAN4_2_SHIFT, 4, 1),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64MMFR0_TGRAN64_2_SHIFT, 4, 1),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64MMFR0_TGRAN16_2_SHIFT, 4, 1),
/*
* We already refuse to boot CPUs that don't support our configured
* page size, so we can only detect mismatches for a page size other
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 30b7ea680f66c..241db35a7ef4f 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -9,6 +9,7 @@
*/

#include <linux/errno.h>
+#include <linux/bitfield.h>
#include <linux/kernel.h>
#include <linux/kvm_host.h>
#include <linux/kvm.h>
@@ -340,11 +341,42 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
return ret;
}

-void kvm_set_ipa_limit(void)
+int kvm_set_ipa_limit(void)
{
- unsigned int ipa_max, pa_max, va_max, parange;
+ unsigned int ipa_max, pa_max, va_max, parange, tgran_2;
+ u64 mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);

- parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 0x7;
+ /*
+ * Check with ARMv8.5-GTG that our PAGE_SIZE is supported at
+ * Stage-2. If not, things will stop very quickly.
+ */
+ switch (PAGE_SIZE) {
+ default:
+ case SZ_4K:
+ tgran_2 = ID_AA64MMFR0_TGRAN4_2_SHIFT;
+ break;
+ case SZ_16K:
+ tgran_2 = ID_AA64MMFR0_TGRAN16_2_SHIFT;
+ break;
+ case SZ_64K:
+ tgran_2 = ID_AA64MMFR0_TGRAN64_2_SHIFT;
+ break;
+ }
+
+ switch (FIELD_GET(0xFUL << tgran_2, mmfr0)) {
+ default:
+ case 1:
+ kvm_err("PAGE_SIZE not supported at Stage-2, giving up\n");
+ return -EINVAL;
+ case 0:
+ kvm_debug("PAGE_SIZE supported at Stage-2 (default)\n");
+ break;
+ case 2:
+ kvm_debug("PAGE_SIZE supported at Stage-2 (advertised)\n");
+ break;
+ }
+
+ parange = mmfr0 & 0x7;
pa_max = id_aa64mmfr0_parange_to_phys_shift(parange);

/* Clamp the IPA limit to the PA size supported by the kernel */
@@ -378,6 +410,8 @@ void kvm_set_ipa_limit(void)
"KVM IPA limit (%d bit) is smaller than default size\n", ipa_max);
kvm_ipa_limit = ipa_max;
kvm_info("IPA Size Limit: %dbits\n", kvm_ipa_limit);
+
+ return 0;
}

/*
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 48d0ec44ad77e..53b3ba9173ba7 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1387,9 +1387,7 @@ static inline void hyp_cpu_pm_exit(void)

static int init_common_resources(void)
{
- kvm_set_ipa_limit();
-
- return 0;
+ return kvm_set_ipa_limit();
}

static int init_subsystems(void)
--
2.26.1