Re: [PATCH v7 12/23] iommu/smmuv3: Get prepared for nested stage support

Robin Murphy
2019-05-08T14:24:12Z

On 08/04/2019 13:19, Eric Auger wrote:
> To allow nested stage support, we need to store both
> stage 1 and stage 2 configurations (and remove the former
> union).
>
> A nested setup is characterized by both s1_cfg and s2_cfg
> set.
>
> We introduce a new ste.abort field that will be set upon
> guest stage1 configuration passing. If s1_cfg is NULL and
> ste.abort is set, traffic can't pass. If ste.abort is not set,
> S1 is bypassed.
>
> arm_smmu_write_strtab_ent() is modified to write both stage
> fields in the STE and deal with the abort field.
>
> In nested mode, only stage 2 is "finalized" as the host does
> not own/configure the stage 1 context descriptor, guest does.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> v4 -> v5:
> - reset ste.abort on detach
>
> v3 -> v4:
> - s1_cfg.nested_abort and nested_bypass removed.
> - s/ste.nested/ste.abort
> - arm_smmu_write_strtab_ent modifications with introduction
> of local abort, bypass and translate local variables
> - comment updated
>
> 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 | 35 ++++++++++++++++++++---------------
> 1 file changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 21d027695181..e22e944ffc05 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -211,6 +211,7 @@
> #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
> @@ -514,6 +515,7 @@ struct arm_smmu_strtab_ent {
> * configured according to the domain type.
> */
> bool assigned;
> + bool abort;
> struct arm_smmu_s1_cfg *s1_cfg;
> struct arm_smmu_s2_cfg *s2_cfg;
> };
> @@ -628,10 +630,8 @@ 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;
>
> @@ -1108,12 +1108,13 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> __le64 *dst, struct arm_smmu_strtab_ent *ste)
> {
> /*
> - * This is hideously complicated, but we only really care about
> - * three cases at the moment:
> + * We care about the following transitions:
> *
> * 1. Invalid (all zero) -> bypass/fault (init)
> - * 2. Bypass/fault -> translation/bypass (attach)
> - * 3. Translation/bypass -> bypass/fault (detach)
> + * 2. Bypass/fault -> single stage translation/bypass (attach)
> + * 3. single stage Translation/bypass -> bypass/fault (detach)
> + * 4. S2 -> S1 + S2 (attach_pasid_table)
> + * 5. S1 + S2 -> S2 (detach_pasid_table)
> *
> * Given that we can't update the STE atomically and the SMMU
> * doesn't read the thing in a defined order, that leaves us
> @@ -1124,7 +1125,7 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> * 3. Update Config, sync
> */
> u64 val = le64_to_cpu(dst[0]);
> - bool ste_live = false;
> + bool abort, bypass, translate, ste_live = false;
> struct arm_smmu_cmdq_ent prefetch_cmd = {
> .opcode = CMDQ_OP_PREFETCH_CFG,
> .prefetch = {
> @@ -1138,11 +1139,11 @@ 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)
> - break;
> + break;
> default:
> BUG(); /* STE corruption */
> }
> @@ -1152,8 +1153,13 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> val = STRTAB_STE_0_V;
>
> /* Bypass/fault */
> - if (!ste->assigned || !(ste->s1_cfg || ste->s2_cfg)) {
> - if (!ste->assigned && disable_bypass)
> +
> + abort = (!ste->assigned && disable_bypass) || ste->abort;
> + translate = ste->s1_cfg || ste->s2_cfg;
> + bypass = !abort && !translate;
> +
> + if (abort || bypass) {
> + if (abort)
> 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);
> @@ -1172,7 +1178,6 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> }
>
> if (ste->s1_cfg) {
> - BUG_ON(ste_live);

Hmm, I'm a little uneasy about just removing these checks altogether, as
there are still cases where rewriting a live entry is bogus, that we'd
really like to keep catching. Is the problem that it's hard to tell when
you're 'rewriting' the S2 config of a nested entry with the same thing
on attaching/detaching its S1 context?

Robin.

> 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) |
> @@ -1191,7 +1196,6 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
> }
>
> 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) |
> @@ -1773,6 +1777,7 @@ static void arm_smmu_detach_dev(struct device *dev)
> }
>
> master->ste.assigned = false;
> + master->ste.abort = false;
> arm_smmu_install_ste_for_dev(fwspec);
> }
>
>