Re: [RFC v3 09/21] iommu/smmuv3: Get prepared for nested stage support

Robin Murphy
2019-01-25T19:27:49Z

On 08/01/2019 10:26, Eric Auger wrote:
> To allow nested stage support, we need to store both
> stage 1 and stage 2 configurations (and remove the former
> union).
>
> arm_smmu_write_strtab_ent() is modified to write both stage
> fields in the STE.
>
> We add a nested_bypass field to the S1 configuration as the first
> stage can be bypassed. Also the guest may force the STE to abort:
> this information gets stored into the nested_abort field.
>
> Only S2 stage is "finalized" as the host does not configure
> S1 CD, guest does.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> v1 -> v2:
> - invalidate the STE before moving from a live STE config to another
> - add the nested_abort and nested_bypass fields
> ---
> drivers/iommu/arm-smmu-v3.c | 43 ++++++++++++++++++++++++++++---------
> 1 file changed, 33 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 9af68266bbb1..9716a301d9ae 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -212,6 +212,7 @@
> #define STRTAB_STE_0_CFG_BYPASS 4
> #define STRTAB_STE_0_CFG_S1_TRANS 5
> #define STRTAB_STE_0_CFG_S2_TRANS 6
> +#define STRTAB_STE_0_CFG_NESTED 7
>
> #define STRTAB_STE_0_S1FMT GENMASK_ULL(5, 4)
> #define STRTAB_STE_0_S1FMT_LINEAR 0
> @@ -491,6 +492,10 @@ struct arm_smmu_strtab_l1_desc {
> struct arm_smmu_s1_cfg {
> __le64 *cdptr;
> dma_addr_t cdptr_dma;
> + /* in nested mode, tells s1 must be bypassed */
> + bool nested_bypass;

Couldn't that be inferred from "s1_cfg == NULL"?

> + /* in nested mode, abort is forced by guest */
> + bool nested_abort;

Couldn't that be inferred from "s1_cfg == NULL && s2_cfg == NULL &&
smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED"?

> struct arm_smmu_ctx_desc {
> u16 asid;
> @@ -515,6 +520,7 @@ struct arm_smmu_strtab_ent {
> * configured according to the domain type.
> */
> bool assigned;
> + bool nested;

AFAICS, "nested" really only serves a differentiator between the
assigned-as-bypass and assigned-as-fault cases. The latter isn't
actually unique to nested though, I'd say it's more just that nobody's
found reason to do anything with IOMMU_DOMAIN_BLOCKED yet. There's some
argument for upgrading "assigned" into a tristate enum, but I think it
might have a few drawbacks elsewhere, so an extra flag here seems
reasonable, but I think it should just be named "abort". If we have both
s1_cfg and s2_cfg set, we can see it's nested; if we only have s2_cfg, I
don't think we really care whether the host or guest asked for stage 1
bypass; and if in future we care about the difference between host- vs.
guest-requested abort, leaving s2_cfg set for the latter would probably
suffice.

> struct arm_smmu_s1_cfg *s1_cfg;
> struct arm_smmu_s2_cfg *s2_cfg;
> };
> @@ -629,10 +635,8 @@ struct arm_smmu_domain {
> bool non_strict;
>
> enum arm_smmu_domain_stage stage;
> - union {
> - struct arm_smmu_s1_cfg s1_cfg;
> - struct arm_smmu_s2_cfg s2_cfg;
> - };
> + struct arm_smmu_s1_cfg s1_cfg;
> + struct arm_smmu_s2_cfg s2_cfg;
>
> struct iommu_domain domain;
>
> @@ -1139,10 +1143,11 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> break;
> case STRTAB_STE_0_CFG_S1_TRANS:
> case STRTAB_STE_0_CFG_S2_TRANS:
> + case STRTAB_STE_0_CFG_NESTED:
> ste_live = true;
> break;
> case STRTAB_STE_0_CFG_ABORT:
> - if (disable_bypass)
> + if (disable_bypass || ste->nested)
> break;
> default:
> BUG(); /* STE corruption */
> @@ -1154,7 +1159,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
>
> /* Bypass/fault */
> if (!ste->assigned || !(ste->s1_cfg || ste->s2_cfg)) {
> - if (!ste->assigned && disable_bypass)
> + if ((!ste->assigned && disable_bypass) ||
> + (ste->s1_cfg && ste->s1_cfg->nested_abort))

Yikes, these conditions were hard enough to follow before...

I think what I've proposed above might allow the logic here to be a bit
less convoluted, but even then it may be time to hoist all these checks
out and have a temporary decision variable for the bypass/abort/valid
config outcome.

Robin.

> val |= FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_ABORT);
> else
> val |= FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_BYPASS);
> @@ -1172,8 +1178,17 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> return;
> }
>
> + if (ste->nested && ste_live) {
> + /*
> + * When enabling nested, the STE may be transitionning from
> + * s2 to nested and back. Invalidate the STE before changing it.
> + */
> + dst[0] = cpu_to_le64(0);
> + arm_smmu_sync_ste_for_sid(smmu, sid);
> + val = STRTAB_STE_0_V;
> + }
> +
> if (ste->s1_cfg) {
> - BUG_ON(ste_live);
> dst[1] = cpu_to_le64(
> FIELD_PREP(STRTAB_STE_1_S1CIR, STRTAB_STE_1_S1C_CACHE_WBRA) |
> FIELD_PREP(STRTAB_STE_1_S1COR, STRTAB_STE_1_S1C_CACHE_WBRA) |
> @@ -1187,12 +1202,12 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> !(smmu->features & ARM_SMMU_FEAT_STALL_FORCE))
> dst[1] |= cpu_to_le64(STRTAB_STE_1_S1STALLD);
>
> - val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK) |
> - FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_S1_TRANS);
> + if (!ste->s1_cfg->nested_bypass)
> + val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK) |
> + FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_S1_TRANS);
> }
>
> if (ste->s2_cfg) {
> - BUG_ON(ste_live);
> dst[2] = cpu_to_le64(
> FIELD_PREP(STRTAB_STE_2_S2VMID, ste->s2_cfg->vmid) |
> FIELD_PREP(STRTAB_STE_2_VTCR, ste->s2_cfg->vtcr) |
> @@ -1454,6 +1469,10 @@ static void arm_smmu_tlb_inv_context(void *cookie)
> cmd.opcode = CMDQ_OP_TLBI_NH_ASID;
> cmd.tlbi.asid = smmu_domain->s1_cfg.cd.asid;
> cmd.tlbi.vmid = 0;
> + } else if (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED) {
> + cmd.opcode = CMDQ_OP_TLBI_NH_ASID;
> + cmd.tlbi.asid = smmu_domain->s1_cfg.cd.asid;
> + cmd.tlbi.vmid = smmu_domain->s2_cfg.vmid;
> } else {
> cmd.opcode = CMDQ_OP_TLBI_S12_VMALL;
> cmd.tlbi.vmid = smmu_domain->s2_cfg.vmid;
> @@ -1484,6 +1503,10 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
> if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1) {
> cmd.opcode = CMDQ_OP_TLBI_NH_VA;
> cmd.tlbi.asid = smmu_domain->s1_cfg.cd.asid;
> + } else if (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED) {
> + cmd.opcode = CMDQ_OP_TLBI_NH_VA;
> + cmd.tlbi.asid = smmu_domain->s1_cfg.cd.asid;
> + cmd.tlbi.vmid = smmu_domain->s2_cfg.vmid;
> } else {
> cmd.opcode = CMDQ_OP_TLBI_S2_IPA;
> cmd.tlbi.vmid = smmu_domain->s2_cfg.vmid;
>