[PATCH v12 06/11] KVM: arm64: Save ID registers' sanitized value per guest
Oliver Upton
oliver.upton at linux.dev
Fri Jun 9 12:00:49 PDT 2023
From: Jing Zhang <jingzhangos at google.com>
Initialize the default ID register values upon the first call to
KVM_ARM_VCPU_INIT. The vCPU feature flags are finalized at that point,
so it is possible to determine the maximum feature set supported by a
particular VM configuration. Do nothing with these values for now, as we
need to rework the plumbing of what's already writable to be compatible
with the generic infrastructure.
Co-developed-by: Reiji Watanabe <reijiw at google.com>
Signed-off-by: Reiji Watanabe <reijiw at google.com>
Signed-off-by: Jing Zhang <jingzhangos at google.com>
[Oliver: Hoist everything into KVM_ARM_VCPU_INIT time, so the features
are final]
Signed-off-by: Oliver Upton <oliver.upton at linux.dev>
---
arch/arm64/include/asm/kvm_host.h | 15 +++++++++
arch/arm64/kvm/sys_regs.c | 56 +++++++++++++++++++++++++++++--
arch/arm64/kvm/sys_regs.h | 7 ++++
3 files changed, 75 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 44da989435fc..39270bc29a3f 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -225,6 +225,8 @@ struct kvm_arch {
#define KVM_ARCH_FLAG_TIMER_PPIS_IMMUTABLE 6
/* SMCCC filter initialized for the VM */
#define KVM_ARCH_FLAG_SMCCC_FILTER_CONFIGURED 7
+ /* Initial ID reg values loaded */
+#define KVM_ARCH_FLAG_ID_REGS_INITIALIZED 8
unsigned long flags;
/* VM-wide vCPU feature set */
@@ -247,6 +249,19 @@ struct kvm_arch {
struct kvm_smccc_features smccc_feat;
struct maple_tree smccc_filter;
+ /*
+ * Emulated CPU ID registers per VM
+ * (Op0, Op1, CRn, CRm, Op2) of the ID registers to be saved in it
+ * is (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8.
+ *
+ * These emulated idregs are VM-wide, but accessed from the context of a vCPU.
+ * Atomic access to multiple idregs are guarded by kvm_arch.config_lock.
+ */
+#define IDREG_IDX(id) (((sys_reg_CRm(id) - 1) << 3) | sys_reg_Op2(id))
+#define IDREG(kvm, id) ((kvm)->arch.id_regs[IDREG_IDX(id)])
+#define KVM_ARM_ID_REG_NUM (IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1)
+ u64 id_regs[KVM_ARM_ID_REG_NUM];
+
/*
* For an untrusted host VM, 'pkvm.handle' is used to lookup
* the associated pKVM instance in the hypervisor.
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 9d37f16cfb7b..3015c860deca 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1311,6 +1311,17 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r
return __kvm_read_sanitised_id_reg(vcpu, r);
}
+/*
+ * Return true if the register's (Op0, Op1, CRn, CRm, Op2) is
+ * (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8.
+ */
+static inline bool is_id_reg(u32 id)
+{
+ return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 &&
+ sys_reg_CRn(id) == 0 && sys_reg_CRm(id) >= 1 &&
+ sys_reg_CRm(id) < 8);
+}
+
static unsigned int id_visibility(const struct kvm_vcpu *vcpu,
const struct sys_reg_desc *r)
{
@@ -2303,6 +2314,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
EL2_REG(SP_EL2, NULL, reset_unknown, 0),
};
+static const struct sys_reg_desc *first_idreg;
+
static bool trap_dbgdidr(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
@@ -2993,6 +3006,28 @@ static bool emulate_sys_reg(struct kvm_vcpu *vcpu,
return false;
}
+static void kvm_reset_id_regs(struct kvm_vcpu *vcpu)
+{
+ const struct sys_reg_desc *idreg = first_idreg;
+ u32 id = reg_to_encoding(idreg);
+ struct kvm *kvm = vcpu->kvm;
+
+ if (test_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags))
+ return;
+
+ lockdep_assert_held(&kvm->arch.config_lock);
+
+ /* Initialize all idregs */
+ while (is_id_reg(id)) {
+ IDREG(kvm, id) = idreg->reset(vcpu, idreg);
+
+ idreg++;
+ id = reg_to_encoding(idreg);
+ }
+
+ set_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags);
+}
+
/**
* kvm_reset_sys_regs - sets system registers to reset value
* @vcpu: The VCPU pointer
@@ -3004,9 +3039,17 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu)
{
unsigned long i;
- for (i = 0; i < ARRAY_SIZE(sys_reg_descs); i++)
- if (sys_reg_descs[i].reset)
- sys_reg_descs[i].reset(vcpu, &sys_reg_descs[i]);
+ kvm_reset_id_regs(vcpu);
+
+ for (i = 0; i < ARRAY_SIZE(sys_reg_descs); i++) {
+ const struct sys_reg_desc *r = &sys_reg_descs[i];
+
+ if (is_id_reg(reg_to_encoding(r)))
+ continue;
+
+ if (r->reset)
+ r->reset(vcpu, r);
+ }
}
/**
@@ -3413,6 +3456,7 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
int __init kvm_sys_reg_table_init(void)
{
+ struct sys_reg_params params;
bool valid = true;
unsigned int i;
@@ -3431,5 +3475,11 @@ int __init kvm_sys_reg_table_init(void)
for (i = 0; i < ARRAY_SIZE(invariant_sys_regs); i++)
invariant_sys_regs[i].reset(NULL, &invariant_sys_regs[i]);
+ /* Find the first idreg (SYS_ID_PFR0_EL1) in sys_reg_descs. */
+ params = encoding_to_params(SYS_ID_PFR0_EL1);
+ first_idreg = find_reg(¶ms, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+ if (!first_idreg)
+ return -EINVAL;
+
return 0;
}
diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index 63bca7521dfd..c65c129b3500 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -27,6 +27,13 @@ struct sys_reg_params {
bool is_write;
};
+#define encoding_to_params(reg) \
+ ((struct sys_reg_params){ .Op0 = sys_reg_Op0(reg), \
+ .Op1 = sys_reg_Op1(reg), \
+ .CRn = sys_reg_CRn(reg), \
+ .CRm = sys_reg_CRm(reg), \
+ .Op2 = sys_reg_Op2(reg) })
+
#define esr_sys64_to_params(esr) \
((struct sys_reg_params){ .Op0 = ((esr) >> 20) & 3, \
.Op1 = ((esr) >> 14) & 0x7, \
--
2.41.0.162.gfafddb0af9-goog
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