Re: [PATCH v7 1/9] iommu/arm-smmu-v3: Add an ops indirection to the STE code

Mostafa Saleh
2024-04-19T21:02:59Z

Hi Jason,

On Tue, Apr 16, 2024 at 04:28:12PM -0300, Jason Gunthorpe wrote:
> Prepare to put the CD code into the same mechanism. Add an ops indirection
> around all the STE specific code and make the worker functions independent
> of the entry content being processed.
>
> get_used and sync ops are provided to hook the correct code.
>
> Signed-off-by: Michael Shavit <mshavit@google.com>
> Reviewed-by: Michael Shavit <mshavit@google.com>
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 178 ++++++++++++--------
> 1 file changed, 106 insertions(+), 72 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 79c18e95dd293e..bf105e914d38b1 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -42,8 +42,20 @@ enum arm_smmu_msi_index {
> ARM_SMMU_MAX_MSIS,
> };
>
> -static void arm_smmu_sync_ste_for_sid(struct arm_smmu_device *smmu,
> - ioasid_t sid);
> +struct arm_smmu_entry_writer_ops;
> +struct arm_smmu_entry_writer {
> + const struct arm_smmu_entry_writer_ops *ops;
> + struct arm_smmu_master *master;
> +};
> +
> +struct arm_smmu_entry_writer_ops {
> + __le64 v_bit;
> + void (*get_used)(const __le64 *entry, __le64 *used);
> + void (*sync)(struct arm_smmu_entry_writer *writer);
> +};
> +
> +#define NUM_ENTRY_QWORDS 8
> +static_assert(sizeof(struct arm_smmu_ste) == NUM_ENTRY_QWORDS * sizeof(u64));
>
> static phys_addr_t arm_smmu_msi_cfg[ARM_SMMU_MAX_MSIS][3] = {
> [EVTQ_MSI_INDEX] = {
> @@ -972,43 +984,42 @@ void arm_smmu_tlb_inv_asid(struct arm_smmu_device *smmu, u16 asid)
> * would be nice if this was complete according to the spec, but minimally it
> * has to capture the bits this driver uses.
> */
> -static void arm_smmu_get_ste_used(const struct arm_smmu_ste *ent,
> - struct arm_smmu_ste *used_bits)
> +static void arm_smmu_get_ste_used(const __le64 *ent, __le64 *used_bits)
> {
> - unsigned int cfg = FIELD_GET(STRTAB_STE_0_CFG, le64_to_cpu(ent->data[0]));
> + unsigned int cfg = FIELD_GET(STRTAB_STE_0_CFG, le64_to_cpu(ent[0]));
>
> - used_bits->data[0] = cpu_to_le64(STRTAB_STE_0_V);
> - if (!(ent->data[0] & cpu_to_le64(STRTAB_STE_0_V)))
> + used_bits[0] = cpu_to_le64(STRTAB_STE_0_V);
> + if (!(ent[0] & cpu_to_le64(STRTAB_STE_0_V)))
> return;
>
> - used_bits->data[0] |= cpu_to_le64(STRTAB_STE_0_CFG);
> + used_bits[0] |= cpu_to_le64(STRTAB_STE_0_CFG);
>
> /* S1 translates */
> if (cfg & BIT(0)) {
> - used_bits->data[0] |= cpu_to_le64(STRTAB_STE_0_S1FMT |
> - STRTAB_STE_0_S1CTXPTR_MASK |
> - STRTAB_STE_0_S1CDMAX);
> - used_bits->data[1] |=
> + used_bits[0] |= cpu_to_le64(STRTAB_STE_0_S1FMT |
> + STRTAB_STE_0_S1CTXPTR_MASK |
> + STRTAB_STE_0_S1CDMAX);
> + used_bits[1] |=
> cpu_to_le64(STRTAB_STE_1_S1DSS | STRTAB_STE_1_S1CIR |
> STRTAB_STE_1_S1COR | STRTAB_STE_1_S1CSH |
> STRTAB_STE_1_S1STALLD | STRTAB_STE_1_STRW |
> STRTAB_STE_1_EATS);
> - used_bits->data[2] |= cpu_to_le64(STRTAB_STE_2_S2VMID);
> + used_bits[2] |= cpu_to_le64(STRTAB_STE_2_S2VMID);
> }
>
> /* S2 translates */
> if (cfg & BIT(1)) {
> - used_bits->data[1] |=
> + used_bits[1] |=
> cpu_to_le64(STRTAB_STE_1_EATS | STRTAB_STE_1_SHCFG);
> - used_bits->data[2] |=
> + used_bits[2] |=
> cpu_to_le64(STRTAB_STE_2_S2VMID | STRTAB_STE_2_VTCR |
> STRTAB_STE_2_S2AA64 | STRTAB_STE_2_S2ENDI |
> STRTAB_STE_2_S2PTW | STRTAB_STE_2_S2R);
> - used_bits->data[3] |= cpu_to_le64(STRTAB_STE_3_S2TTB_MASK);
> + used_bits[3] |= cpu_to_le64(STRTAB_STE_3_S2TTB_MASK);
> }
>
> if (cfg == STRTAB_STE_0_CFG_BYPASS)
> - used_bits->data[1] |= cpu_to_le64(STRTAB_STE_1_SHCFG);
> + used_bits[1] |= cpu_to_le64(STRTAB_STE_1_SHCFG);
> }
>
> /*
> @@ -1017,57 +1028,55 @@ static void arm_smmu_get_ste_used(const struct arm_smmu_ste *ent,
> * unused_update is an intermediate value of entry that has unused bits set to
> * their new values.
> */
> -static u8 arm_smmu_entry_qword_diff(const struct arm_smmu_ste *entry,
> - const struct arm_smmu_ste *target,
> - struct arm_smmu_ste *unused_update)
> +static u8 arm_smmu_entry_qword_diff(struct arm_smmu_entry_writer *writer,
> + const __le64 *entry, const __le64 *target,
> + __le64 *unused_update)
> {
> - struct arm_smmu_ste target_used = {};
> - struct arm_smmu_ste cur_used = {};
> + __le64 target_used[NUM_ENTRY_QWORDS] = {};
> + __le64 cur_used[NUM_ENTRY_QWORDS] = {};
> u8 used_qword_diff = 0;
> unsigned int i;
>
> - arm_smmu_get_ste_used(entry, &cur_used);
> - arm_smmu_get_ste_used(target, &target_used);
> + writer->ops->get_used(entry, cur_used);
> + writer->ops->get_used(target, target_used);
>
> - for (i = 0; i != ARRAY_SIZE(target_used.data); i++) {
> + for (i = 0; i != NUM_ENTRY_QWORDS; i++) {
> /*
> * Check that masks are up to date, the make functions are not
> * allowed to set a bit to 1 if the used function doesn't say it
> * is used.
> */
> - WARN_ON_ONCE(target->data[i] & ~target_used.data[i]);
> + WARN_ON_ONCE(target[i] & ~target_used[i]);
>
> /* Bits can change because they are not currently being used */
> - unused_update->data[i] = (entry->data[i] & cur_used.data[i]) |
> - (target->data[i] & ~cur_used.data[i]);
> + unused_update[i] = (entry[i] & cur_used[i]) |
> + (target[i] & ~cur_used[i]);
> /*
> * Each bit indicates that a used bit in a qword needs to be
> * changed after unused_update is applied.
> */
> - if ((unused_update->data[i] & target_used.data[i]) !=
> - target->data[i])
> + if ((unused_update[i] & target_used[i]) != target[i])
> used_qword_diff |= 1 << i;
> }
> return used_qword_diff;
> }
>
> -static bool entry_set(struct arm_smmu_device *smmu, ioasid_t sid,
> - struct arm_smmu_ste *entry,
> - const struct arm_smmu_ste *target, unsigned int start,
> +static bool entry_set(struct arm_smmu_entry_writer *writer, __le64 *entry,
> + const __le64 *target, unsigned int start,
> unsigned int len)
> {
> bool changed = false;
> unsigned int i;
>
> for (i = start; len != 0; len--, i++) {
> - if (entry->data[i] != target->data[i]) {
> - WRITE_ONCE(entry->data[i], target->data[i]);
> + if (entry[i] != target[i]) {
> + WRITE_ONCE(entry[i], target[i]);
> changed = true;
> }
> }
>
> if (changed)
> - arm_smmu_sync_ste_for_sid(smmu, sid);
> + writer->ops->sync(writer);
> return changed;
> }
>
> @@ -1097,24 +1106,21 @@ static bool entry_set(struct arm_smmu_device *smmu, ioasid_t sid,
> * V=0 process. This relies on the IGNORED behavior described in the
> * specification.
> */
> -static void arm_smmu_write_ste(struct arm_smmu_master *master, u32 sid,
> - struct arm_smmu_ste *entry,
> - const struct arm_smmu_ste *target)
> +static void arm_smmu_write_entry(struct arm_smmu_entry_writer *writer,
> + __le64 *entry, const __le64 *target)
> {
> - unsigned int num_entry_qwords = ARRAY_SIZE(target->data);
> - struct arm_smmu_device *smmu = master->smmu;
> - struct arm_smmu_ste unused_update;
> + __le64 unused_update[NUM_ENTRY_QWORDS];
> u8 used_qword_diff;
>
> used_qword_diff =
> - arm_smmu_entry_qword_diff(entry, target, &unused_update);
> + arm_smmu_entry_qword_diff(writer, entry, target, unused_update);
> if (hweight8(used_qword_diff) == 1) {
> /*
> * Only one qword needs its used bits to be changed. This is a
> - * hitless update, update all bits the current STE is ignoring
> - * to their new values, then update a single "critical qword" to
> - * change the STE and finally 0 out any bits that are now unused
> - * in the target configuration.
> + * hitless update, update all bits the current STE/CD is
> + * ignoring to their new values, then update a single "critical
> + * qword" to change the STE/CD and finally 0 out any bits that
> + * are now unused in the target configuration.
> */
> unsigned int critical_qword_index = ffs(used_qword_diff) - 1;
>
> @@ -1123,22 +1129,21 @@ static void arm_smmu_write_ste(struct arm_smmu_master *master, u32 sid,
> * writing it in the next step anyways. This can save a sync
> * when the only change is in that qword.
> */
> - unused_update.data[critical_qword_index] =
> - entry->data[critical_qword_index];
> - entry_set(smmu, sid, entry, &unused_update, 0, num_entry_qwords);
> - entry_set(smmu, sid, entry, target, critical_qword_index, 1);
> - entry_set(smmu, sid, entry, target, 0, num_entry_qwords);
> + unused_update[critical_qword_index] =
> + entry[critical_qword_index];
> + entry_set(writer, entry, unused_update, 0, NUM_ENTRY_QWORDS);
> + entry_set(writer, entry, target, critical_qword_index, 1);
> + entry_set(writer, entry, target, 0, NUM_ENTRY_QWORDS);
> } else if (used_qword_diff) {
> /*
> * At least two qwords need their inuse bits to be changed. This
> * requires a breaking update, zero the V bit, write all qwords
> * but 0, then set qword 0
> */
> - unused_update.data[0] = entry->data[0] &
> - cpu_to_le64(~STRTAB_STE_0_V);
> - entry_set(smmu, sid, entry, &unused_update, 0, 1);
> - entry_set(smmu, sid, entry, target, 1, num_entry_qwords - 1);
> - entry_set(smmu, sid, entry, target, 0, 1);
> + unused_update[0] = entry[0] & (~writer->ops->v_bit);

arm_smmu_write_entry() assumes that v_bit is in entry[0] and that “1” means valid
(which is true for both STE and CD) so why do we care about it, if we break the
STE/CD anyway, why not just do:

unused_update[0] = 0;
entry_set(writer, entry, unused_update, 0, 1);
entry_set(writer, entry, target, 1, NUM_ENTRY_QWORDS - 1)
entry_set(writer, entry, target, 0, 1);

That makes the code simpler by avoiding having the v_bit in
arm_smmu_entry_writer_ops.

Thanks,
Mostafa

> + entry_set(writer, entry, unused_update, 0, 1);
> + entry_set(writer, entry, target, 1, NUM_ENTRY_QWORDS - 1);
> + entry_set(writer, entry, target, 0, 1);
> } else {
> /*
> * No inuse bit changed. Sanity check that all unused bits are 0
> @@ -1146,18 +1151,7 @@ static void arm_smmu_write_ste(struct arm_smmu_master *master, u32 sid,
> * compute_qword_diff().
> */
> WARN_ON_ONCE(
> - entry_set(smmu, sid, entry, target, 0, num_entry_qwords));
> - }
> -
> - /* It's likely that we'll want to use the new STE soon */
> - if (!(smmu->options & ARM_SMMU_OPT_SKIP_PREFETCH)) {
> - struct arm_smmu_cmdq_ent
> - prefetch_cmd = { .opcode = CMDQ_OP_PREFETCH_CFG,
> - .prefetch = {
> - .sid = sid,
> - } };
> -
> - arm_smmu_cmdq_issue_cmd(smmu, &prefetch_cmd);
> + entry_set(writer, entry, target, 0, NUM_ENTRY_QWORDS));
> }
> }
>
> @@ -1430,17 +1424,57 @@ arm_smmu_write_strtab_l1_desc(__le64 *dst, struct arm_smmu_strtab_l1_desc *desc)
> WRITE_ONCE(*dst, cpu_to_le64(val));
> }
>
> -static void arm_smmu_sync_ste_for_sid(struct arm_smmu_device *smmu, u32 sid)
> +struct arm_smmu_ste_writer {
> + struct arm_smmu_entry_writer writer;
> + u32 sid;
> +};
> +
> +static void arm_smmu_ste_writer_sync_entry(struct arm_smmu_entry_writer *writer)
> {
> + struct arm_smmu_ste_writer *ste_writer =
> + container_of(writer, struct arm_smmu_ste_writer, writer);
> struct arm_smmu_cmdq_ent cmd = {
> .opcode = CMDQ_OP_CFGI_STE,
> .cfgi = {
> - .sid = sid,
> + .sid = ste_writer->sid,
> .leaf = true,
> },
> };
>
> - arm_smmu_cmdq_issue_cmd_with_sync(smmu, &cmd);
> + arm_smmu_cmdq_issue_cmd_with_sync(writer->master->smmu, &cmd);
> +}
> +
> +static const struct arm_smmu_entry_writer_ops arm_smmu_ste_writer_ops = {
> + .sync = arm_smmu_ste_writer_sync_entry,
> + .get_used = arm_smmu_get_ste_used,
> + .v_bit = cpu_to_le64(STRTAB_STE_0_V),
> +};
> +
> +static void arm_smmu_write_ste(struct arm_smmu_master *master, u32 sid,
> + struct arm_smmu_ste *ste,
> + const struct arm_smmu_ste *target)
> +{
> + struct arm_smmu_device *smmu = master->smmu;
> + struct arm_smmu_ste_writer ste_writer = {
> + .writer = {
> + .ops = &arm_smmu_ste_writer_ops,
> + .master = master,
> + },
> + .sid = sid,
> + };
> +
> + arm_smmu_write_entry(&ste_writer.writer, ste->data, target->data);
> +
> + /* It's likely that we'll want to use the new STE soon */
> + if (!(smmu->options & ARM_SMMU_OPT_SKIP_PREFETCH)) {
> + struct arm_smmu_cmdq_ent
> + prefetch_cmd = { .opcode = CMDQ_OP_PREFETCH_CFG,
> + .prefetch = {
> + .sid = sid,
> + } };
> +
> + arm_smmu_cmdq_issue_cmd(smmu, &prefetch_cmd);
> + }
> }
>
> static void arm_smmu_make_abort_ste(struct arm_smmu_ste *target)
> --
> 2.43.2