KVM: arm64: Treat CTR_EL0 as a VM feature ID register

CTR_EL0 is currently handled as an invariant register, thus
guests will be presented with the host value of that register.

Add emulation for CTR_EL0 based on a per VM value. Userspace can
switch off DIC and IDC bits and reduce DminLine and IminLine sizes.
Naturally, ensure CTR_EL0 is trapped (HCR_EL2.TID2=1) any time that a
VM's CTR_EL0 differs from hardware.

Signed-off-by: Sebastian Ott <sebott@redhat.com>
Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
Link: https://lore.kernel.org/r/20240619174036.483943-8-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 26042875d6fc4c4b357ad4730433935def9083f0..f6de08e81d49f085b854ef49e82aa34392788eb8 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -329,6 +329,8 @@ struct kvm_arch {
 #define KVM_ARM_ID_REG_NUM     (IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1)
        u64 id_regs[KVM_ARM_ID_REG_NUM];
 
+       u64 ctr_el0;
+
        /* Masks for VNCR-baked sysregs */
        struct kvm_sysreg_masks *sysreg_masks;
 
@@ -1335,6 +1337,8 @@ static inline u64 *__vm_id_reg(struct kvm_arch *ka, u32 reg)
        switch (reg) {
        case sys_reg(3, 0, 0, 1, 0) ... sys_reg(3, 0, 0, 7, 7):
                return &ka->id_regs[IDREG_IDX(reg)];
+       case SYS_CTR_EL0:
+               return &ka->ctr_el0;
        default:
                WARN_ON_ONCE(1);
                return NULL;

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index a467ff4290a7201c41fea7428f28464f3d4492a1..a12f3bdfb43d279a0eda6ba80095fe5d511ac25e 100644 (file)
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1583,6 +1583,9 @@ static bool is_feature_id_reg(u32 encoding)
  */
 static inline bool is_vm_ftr_id_reg(u32 id)
 {
+       if (id == SYS_CTR_EL0)
+               return true;
+
        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);
@@ -1898,7 +1901,7 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
        if (p->is_write)
                return write_to_read_only(vcpu, p, r);
 
-       p->regval = read_sanitised_ftr_reg(SYS_CTR_EL0);
+       p->regval = kvm_read_vm_id_reg(vcpu->kvm, SYS_CTR_EL0);
        return true;
 }
 
@@ -2487,7 +2490,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
        { SYS_DESC(SYS_CCSIDR2_EL1), undef_access },
        { SYS_DESC(SYS_SMIDR_EL1), undef_access },
        { SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
-       { SYS_DESC(SYS_CTR_EL0), access_ctr },
+       ID_WRITABLE(CTR_EL0, CTR_EL0_DIC_MASK |
+                            CTR_EL0_IDC_MASK |
+                            CTR_EL0_DminLine_MASK |
+                            CTR_EL0_IminLine_MASK),
        { SYS_DESC(SYS_SVCR), undef_access },
 
        { PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
@@ -3725,18 +3731,11 @@ FUNCTION_INVARIANT(midr_el1)
 FUNCTION_INVARIANT(revidr_el1)
 FUNCTION_INVARIANT(aidr_el1)
 
-static u64 get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r)
-{
-       ((struct sys_reg_desc *)r)->val = read_sanitised_ftr_reg(SYS_CTR_EL0);
-       return ((struct sys_reg_desc *)r)->val;
-}
-
 /* ->val is filled in by kvm_sys_reg_table_init() */
 static struct sys_reg_desc invariant_sys_regs[] __ro_after_init = {
        { SYS_DESC(SYS_MIDR_EL1), NULL, get_midr_el1 },
        { SYS_DESC(SYS_REVIDR_EL1), NULL, get_revidr_el1 },
        { SYS_DESC(SYS_AIDR_EL1), NULL, get_aidr_el1 },
-       { SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 },
 };
 
 static int get_invariant_sys_reg(u64 id, u64 __user *uaddr)
@@ -4086,7 +4085,8 @@ static void vcpu_set_hcr(struct kvm_vcpu *vcpu)
                vcpu->arch.hcr_el2 |= HCR_FWB;
 
        if (cpus_have_final_cap(ARM64_HAS_EVT) &&
-           !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE))
+           !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE) &&
+           kvm_read_vm_id_reg(kvm, SYS_CTR_EL0) == read_sanitised_ftr_reg(SYS_CTR_EL0))
                vcpu->arch.hcr_el2 |= HCR_TID4;
        else
                vcpu->arch.hcr_el2 |= HCR_TID2;