On Fri, 17 Mar 2023 05:06:36 +0000,
Jing Zhang <jingzhangos@xxxxxxxxxx> wrote:
>
> Introduce an ID feature register specific descriptor to include ID
> register specific fields and callbacks besides its corresponding
> general system register descriptor.
> New fields for ID register descriptor would be added later when it
> is necessary to support a writable ID register.
What would these be? Could they make sense for "normal" sysregs as
well?
>
> No functional change intended.
>
> Co-developed-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
> Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
> Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
> ---
> arch/arm64/kvm/id_regs.c | 187 +++++++++++++++++++++++++++-----------
> arch/arm64/kvm/sys_regs.c | 2 +-
> arch/arm64/kvm/sys_regs.h | 1 +
> 3 files changed, 138 insertions(+), 52 deletions(-)
>
> diff --git a/arch/arm64/kvm/id_regs.c b/arch/arm64/kvm/id_regs.c
> index 3a87a3d2390d..9956c99d20f7 100644
> --- a/arch/arm64/kvm/id_regs.c
> +++ b/arch/arm64/kvm/id_regs.c
> @@ -18,6 +18,10 @@
>
> #include "sys_regs.h"
>
> +struct id_reg_desc {
> + const struct sys_reg_desc reg_desc;
> +};
> +
What is the advantage in having this wrapping structure that forces us
to reinvent the wheel (the structure is different) over an additional
pointer or even a side table?
> static u8 vcpu_pmuver(const struct kvm_vcpu *vcpu)
> {
> if (kvm_vcpu_has_pmu(vcpu))
> @@ -334,21 +338,25 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
> }
>
> /* sys_reg_desc initialiser for known cpufeature ID registers */
> -#define ID_SANITISED(name) { \
> - SYS_DESC(SYS_##name), \
> - .access = access_id_reg, \
> - .get_user = get_id_reg, \
> - .set_user = set_id_reg, \
> - .visibility = id_visibility, \
> +#define ID_SANITISED(name) { \
> + .reg_desc = { \
> + SYS_DESC(SYS_##name), \
> + .access = access_id_reg, \
> + .get_user = get_id_reg, \
> + .set_user = set_id_reg, \
> + .visibility = id_visibility, \
> + }, \
> }
>
> /* sys_reg_desc initialiser for known cpufeature ID registers */
> -#define AA32_ID_SANITISED(name) { \
> - SYS_DESC(SYS_##name), \
> - .access = access_id_reg, \
> - .get_user = get_id_reg, \
> - .set_user = set_id_reg, \
> - .visibility = aa32_id_visibility, \
> +#define AA32_ID_SANITISED(name) { \
> + .reg_desc = { \
> + SYS_DESC(SYS_##name), \
> + .access = access_id_reg, \
> + .get_user = get_id_reg, \
> + .set_user = set_id_reg, \
> + .visibility = aa32_id_visibility, \
> + }, \
> }
>
> /*
> @@ -356,12 +364,14 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
> * register with encoding Op0=3, Op1=0, CRn=0, CRm=crm, Op2=op2
> * (1 <= crm < 8, 0 <= Op2 < 8).
> */
> -#define ID_UNALLOCATED(crm, op2) { \
> - Op0(3), Op1(0), CRn(0), CRm(crm), Op2(op2), \
> - .access = access_id_reg, \
> - .get_user = get_id_reg, \
> - .set_user = set_id_reg, \
> - .visibility = raz_visibility \
> +#define ID_UNALLOCATED(crm, op2) { \
> + .reg_desc = { \
> + Op0(3), Op1(0), CRn(0), CRm(crm), Op2(op2), \
> + .access = access_id_reg, \
> + .get_user = get_id_reg, \
> + .set_user = set_id_reg, \
> + .visibility = raz_visibility \
> + }, \
> }
>
> /*
> @@ -369,15 +379,17 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
> * For now, these are exposed just like unallocated ID regs: they appear
> * RAZ for the guest.
> */
> -#define ID_HIDDEN(name) { \
> - SYS_DESC(SYS_##name), \
> - .access = access_id_reg, \
> - .get_user = get_id_reg, \
> - .set_user = set_id_reg, \
> - .visibility = raz_visibility, \
> +#define ID_HIDDEN(name) { \
> + .reg_desc = { \
> + SYS_DESC(SYS_##name), \
> + .access = access_id_reg, \
> + .get_user = get_id_reg, \
> + .set_user = set_id_reg, \
> + .visibility = raz_visibility, \
> + }, \
> }
>
> -static const struct sys_reg_desc id_reg_descs[] = {
> +static const struct id_reg_desc id_reg_descs[KVM_ARM_ID_REG_NUM] = {
> /*
> * ID regs: all ID_SANITISED() entries here must have corresponding
> * entries in arm64_ftr_regs[].
> @@ -387,9 +399,13 @@ static const struct sys_reg_desc id_reg_descs[] = {
> /* CRm=1 */
> AA32_ID_SANITISED(ID_PFR0_EL1),
> AA32_ID_SANITISED(ID_PFR1_EL1),
> - { SYS_DESC(SYS_ID_DFR0_EL1), .access = access_id_reg,
> - .get_user = get_id_reg, .set_user = set_id_dfr0_el1,
> - .visibility = aa32_id_visibility, },
> + { .reg_desc = {
> + SYS_DESC(SYS_ID_DFR0_EL1),
> + .access = access_id_reg,
> + .get_user = get_id_reg,
> + .set_user = set_id_dfr0_el1,
> + .visibility = aa32_id_visibility, },
> + },
> ID_HIDDEN(ID_AFR0_EL1),
> AA32_ID_SANITISED(ID_MMFR0_EL1),
> AA32_ID_SANITISED(ID_MMFR1_EL1),
> @@ -418,8 +434,12 @@ static const struct sys_reg_desc id_reg_descs[] = {
>
> /* AArch64 ID registers */
> /* CRm=4 */
> - { SYS_DESC(SYS_ID_AA64PFR0_EL1), .access = access_id_reg,
> - .get_user = get_id_reg, .set_user = set_id_aa64pfr0_el1, },
> + { .reg_desc = {
> + SYS_DESC(SYS_ID_AA64PFR0_EL1),
> + .access = access_id_reg,
> + .get_user = get_id_reg,
> + .set_user = set_id_aa64pfr0_el1, },
> + },
> ID_SANITISED(ID_AA64PFR1_EL1),
> ID_UNALLOCATED(4, 2),
> ID_UNALLOCATED(4, 3),
> @@ -429,8 +449,12 @@ static const struct sys_reg_desc id_reg_descs[] = {
> ID_UNALLOCATED(4, 7),
>
> /* CRm=5 */
> - { SYS_DESC(SYS_ID_AA64DFR0_EL1), .access = access_id_reg,
> - .get_user = get_id_reg, .set_user = set_id_aa64dfr0_el1, },
> + { .reg_desc = {
> + SYS_DESC(SYS_ID_AA64DFR0_EL1),
> + .access = access_id_reg,
> + .get_user = get_id_reg,
> + .set_user = set_id_aa64dfr0_el1, },
> + },
> ID_SANITISED(ID_AA64DFR1_EL1),
> ID_UNALLOCATED(5, 2),
> ID_UNALLOCATED(5, 3),
> @@ -469,12 +493,12 @@ static const struct sys_reg_desc id_reg_descs[] = {
> */
> int emulate_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *params)
> {
> - const struct sys_reg_desc *r;
> + u32 id;
>
> - r = find_reg(params, id_reg_descs, ARRAY_SIZE(id_reg_descs));
> + id = reg_to_encoding(params);
>
> - if (likely(r)) {
> - perform_access(vcpu, params, r);
> + if (likely(is_id_reg(id))) {
> + perform_access(vcpu, params, &id_reg_descs[IDREG_IDX(id)].reg_desc);
How about minimising the diff and making the whole thing less verbose?
static const struct sys_reg_desc *id_to_id_reg_desc(struct sys_reg_params *params)
{
u32 id;
id = reg_to_encoding(params);
if (is_id_reg(id))
return &id_reg_descs[IDREG_IDX(id)].reg_desc;
return NULL;
}
int emulate_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *params)
{
const struct sys_reg_desc *r;
r = id_to_id_reg_desc(params);
[...]
}
And use the helper everywhere?
> } else {
> print_sys_reg_msg(params,
> "Unsupported guest id_reg access at: %lx [%08lx]\n",
> @@ -491,38 +515,102 @@ void kvm_arm_reset_id_regs(struct kvm_vcpu *vcpu)
> unsigned long i;
>
> for (i = 0; i < ARRAY_SIZE(id_reg_descs); i++)
> - if (id_reg_descs[i].reset)
> - id_reg_descs[i].reset(vcpu, &id_reg_descs[i]);
> + if (id_reg_descs[i].reg_desc.reset)
> + id_reg_descs[i].reg_desc.reset(vcpu, &id_reg_descs[i].reg_desc);
> }
>
> int kvm_arm_get_id_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> {
> - return kvm_sys_reg_get_user(vcpu, reg,
> - id_reg_descs, ARRAY_SIZE(id_reg_descs));
> + u64 __user *uaddr = (u64 __user *)(unsigned long)reg->addr;
> + const struct sys_reg_desc *r;
> + struct sys_reg_params params;
> + u64 val;
> + int ret;
> + u32 id;
> +
> + if (!index_to_params(reg->id, ¶ms))
> + return -ENOENT;
> + id = reg_to_encoding(¶ms);
> +
> + if (!is_id_reg(id))
> + return -ENOENT;
> +
> + r = &id_reg_descs[IDREG_IDX(id)].reg_desc;
> + if (r->get_user) {
> + ret = (r->get_user)(vcpu, r, &val);
> + } else {
> + ret = 0;
> + val = vcpu->kvm->arch.id_regs[IDREG_IDX(id)];
> + }
> +
> + if (!ret)
> + ret = put_user(val, uaddr);
How about the visibility? Why isn't it checked?
> +
> + return ret;
> }
>
> int kvm_arm_set_id_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> {
> - return kvm_sys_reg_set_user(vcpu, reg,
> - id_reg_descs, ARRAY_SIZE(id_reg_descs));
> + u64 __user *uaddr = (u64 __user *)(unsigned long)reg->addr;
> + const struct sys_reg_desc *r;
> + struct sys_reg_params params;
> + u64 val;
> + int ret;
> + u32 id;
> +
> + if (!index_to_params(reg->id, ¶ms))
> + return -ENOENT;
> + id = reg_to_encoding(¶ms);
> +
> + if (!is_id_reg(id))
> + return -ENOENT;
> +
> + if (get_user(val, uaddr))
> + return -EFAULT;
> +
> + r = &id_reg_descs[IDREG_IDX(id)].reg_desc;
> +
> + if (sysreg_user_write_ignore(vcpu, r))
> + return 0;
> +
> + if (r->set_user) {
> + ret = (r->set_user)(vcpu, r, val);
> + } else {
> + WARN_ONCE(1, "ID register set_user callback is NULL\n");
Why the shouting? We didn't do that before. What's changed?
> + ret = 0;
> + }
> +
> + return ret;
> }
>
> bool kvm_arm_check_idreg_table(void)
> {
> - return check_sysreg_table(id_reg_descs, ARRAY_SIZE(id_reg_descs), false);
> + unsigned int i;
> +
> + for (i = 0; i < ARRAY_SIZE(id_reg_descs); i++) {
> + const struct sys_reg_desc *r = &id_reg_descs[i].reg_desc;
> +
> + if (!is_id_reg(reg_to_encoding(r))) {
> + kvm_err("id_reg table %pS entry %d not set correctly\n",
> + &id_reg_descs[i].reg_desc, i);
> + return false;
> + }
> + }
> +
> + return true;
> }
>
> int kvm_arm_walk_id_regs(struct kvm_vcpu *vcpu, u64 __user *uind)
> {
> - const struct sys_reg_desc *i2, *end2;
> + const struct id_reg_desc *i2, *end2;
> unsigned int total = 0;
> int err;
>
> i2 = id_reg_descs;
> end2 = id_reg_descs + ARRAY_SIZE(id_reg_descs);
>
> - while (i2 != end2) {
> - err = walk_one_sys_reg(vcpu, i2++, &uind, &total);
> + for (; i2 != end2; i2++) {
> + err = walk_one_sys_reg(vcpu, &(i2->reg_desc), &uind, &total);
> if (err)
> return err;
> }
> @@ -540,12 +628,9 @@ void kvm_arm_set_default_id_regs(struct kvm *kvm)
> u64 val;
>
> for (i = 0; i < ARRAY_SIZE(id_reg_descs); i++) {
> - id = reg_to_encoding(&id_reg_descs[i]);
> - if (WARN_ON_ONCE(!is_id_reg(id)))
> - /* Shouldn't happen */
> - continue;
> + id = reg_to_encoding(&id_reg_descs[i].reg_desc);
Why have you dropped that check? If it shouldn't happen before, it
still shouldn't happen.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
