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Message-ID: <a0061d0c-2a74-9f32-e6ab-d3d9d06d9fd4@arm.com>
Date: Wed, 16 Aug 2023 22:13:43 +0100
From: Robin Murphy <robin.murphy@....com>
To: Tomasz Jeznach <tjeznach@...osinc.com>,
Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Paul Walmsley <paul.walmsley@...ive.com>
Cc: Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Anup Patel <apatel@...tanamicro.com>,
Sunil V L <sunilvl@...tanamicro.com>,
Nick Kossifidis <mick@....forth.gr>,
Sebastien Boeuf <seb@...osinc.com>, iommu@...ts.linux.dev,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux@...osinc.com
Subject: Re: [PATCH 11/11] RISC-V: drivers/iommu/riscv: Add G-Stage
translation support
On 2023-07-19 20:33, Tomasz Jeznach wrote:
> This change introduces 2nd stage translation configuration
> support, enabling nested translation for IOMMU hardware.
> Pending integration with VMM IOMMUFD interfaces to manage
> 1st stage translation and IOMMU virtialization interfaces.
>
> Signed-off-by: Tomasz Jeznach <tjeznach@...osinc.com>
> ---
> drivers/iommu/riscv/iommu.c | 58 ++++++++++++++++++++++++++++---------
> drivers/iommu/riscv/iommu.h | 3 +-
> 2 files changed, 46 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
> index 7b3e3e135cf6..3ca2f0194d3c 100644
> --- a/drivers/iommu/riscv/iommu.c
> +++ b/drivers/iommu/riscv/iommu.c
> @@ -1418,6 +1418,19 @@ static struct iommu_domain *riscv_iommu_domain_alloc(unsigned type)
> return &domain->domain;
> }
>
> +/* mark domain as second-stage translation */
> +static int riscv_iommu_enable_nesting(struct iommu_domain *iommu_domain)
Please don't add more instances of enable_nesting. It's a dead end that
has never actually been used and should be removed fairly soon. The new
nesting infrastructure is all still in flight, but the current patchsets
should give a good idea of what you'd want to work towards:
https://lore.kernel.org/linux-iommu/20230724110406.107212-1-yi.l.liu@intel.com/
https://lore.kernel.org/linux-iommu/20230724111335.107427-1-yi.l.liu@intel.com/
https://lore.kernel.org/linux-iommu/cover.1683688960.git.nicolinc@nvidia.com/
Thanks,
Robin.
> +{
> + struct riscv_iommu_domain *domain = iommu_domain_to_riscv(iommu_domain);
> +
> + mutex_lock(&domain->lock);
> + if (list_empty(&domain->endpoints))
> + domain->g_stage = true;
> + mutex_unlock(&domain->lock);
> +
> + return domain->g_stage ? 0 : -EBUSY;
> +}
> +
> static void riscv_iommu_domain_free(struct iommu_domain *iommu_domain)
> {
> struct riscv_iommu_domain *domain = iommu_domain_to_riscv(iommu_domain);
> @@ -1433,7 +1446,7 @@ static void riscv_iommu_domain_free(struct iommu_domain *iommu_domain)
> free_io_pgtable_ops(&domain->pgtbl.ops);
>
> if (domain->pgd_root)
> - free_pages((unsigned long)domain->pgd_root, 0);
> + free_pages((unsigned long)domain->pgd_root, domain->g_stage ? 2 : 0);
>
> if ((int)domain->pscid > 0)
> ida_free(&riscv_iommu_pscids, domain->pscid);
> @@ -1483,7 +1496,8 @@ static int riscv_iommu_domain_finalize(struct riscv_iommu_domain *domain,
>
> /* TODO: Fix this for RV32 */
> domain->mode = satp_mode >> 60;
> - domain->pgd_root = (pgd_t *) __get_free_pages(GFP_KERNEL | __GFP_ZERO, 0);
> + domain->pgd_root = (pgd_t *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
> + domain->g_stage ? 2 : 0);
>
> if (!domain->pgd_root)
> return -ENOMEM;
> @@ -1499,6 +1513,8 @@ static u64 riscv_iommu_domain_atp(struct riscv_iommu_domain *domain)
> u64 atp = FIELD_PREP(RISCV_IOMMU_DC_FSC_MODE, domain->mode);
> if (domain->mode != RISCV_IOMMU_DC_FSC_MODE_BARE)
> atp |= FIELD_PREP(RISCV_IOMMU_DC_FSC_PPN, virt_to_pfn(domain->pgd_root));
> + if (domain->g_stage)
> + atp |= FIELD_PREP(RISCV_IOMMU_DC_IOHGATP_GSCID, domain->pscid);
> return atp;
> }
>
> @@ -1541,20 +1557,30 @@ static int riscv_iommu_attach_dev(struct iommu_domain *iommu_domain, struct devi
> if (!dc)
> return -ENODEV;
>
> - /*
> - * S-Stage translation table. G-Stage remains unmodified (BARE).
> - */
> - val = FIELD_PREP(RISCV_IOMMU_DC_TA_PSCID, domain->pscid);
> -
> - if (ep->pasid_enabled) {
> - ep->pc[0].ta = cpu_to_le64(val | RISCV_IOMMU_PC_TA_V);
> - ep->pc[0].fsc = cpu_to_le64(riscv_iommu_domain_atp(domain));
> + if (domain->g_stage) {
> + /*
> + * Enable G-Stage translation with initial pass-through mode
> + * for S-Stage. VMM is responsible for more restrictive
> + * guest VA translation scheme configuration.
> + */
> dc->ta = 0;
> - dc->fsc = cpu_to_le64(virt_to_pfn(ep->pc) |
> - FIELD_PREP(RISCV_IOMMU_DC_FSC_MODE, RISCV_IOMMU_DC_FSC_PDTP_MODE_PD8));
> + dc->fsc = 0ULL; /* RISCV_IOMMU_DC_FSC_MODE_BARE */ ;
> + dc->iohgatp = cpu_to_le64(riscv_iommu_domain_atp(domain));
> } else {
> - dc->ta = cpu_to_le64(val);
> - dc->fsc = cpu_to_le64(riscv_iommu_domain_atp(domain));
> + /* S-Stage translation table. G-Stage remains unmodified. */
> + if (ep->pasid_enabled) {
> + val = FIELD_PREP(RISCV_IOMMU_DC_TA_PSCID, domain->pscid);
> + ep->pc[0].ta = cpu_to_le64(val | RISCV_IOMMU_PC_TA_V);
> + ep->pc[0].fsc = cpu_to_le64(riscv_iommu_domain_atp(domain));
> + dc->ta = 0;
> + val = FIELD_PREP(RISCV_IOMMU_DC_FSC_MODE,
> + RISCV_IOMMU_DC_FSC_PDTP_MODE_PD8);
> + dc->fsc = cpu_to_le64(val | virt_to_pfn(ep->pc));
> + } else {
> + val = FIELD_PREP(RISCV_IOMMU_DC_TA_PSCID, domain->pscid);
> + dc->ta = cpu_to_le64(val);
> + dc->fsc = cpu_to_le64(riscv_iommu_domain_atp(domain));
> + }
> }
>
> wmb();
> @@ -1599,6 +1625,9 @@ static int riscv_iommu_set_dev_pasid(struct iommu_domain *iommu_domain,
> if (!iommu_domain || !iommu_domain->mm)
> return -EINVAL;
>
> + if (domain->g_stage)
> + return -EINVAL;
> +
> /* Driver uses TC.DPE mode, PASID #0 is incorrect. */
> if (pasid == 0)
> return -EINVAL;
> @@ -1969,6 +1998,7 @@ static const struct iommu_domain_ops riscv_iommu_domain_ops = {
> .iotlb_sync = riscv_iommu_iotlb_sync,
> .iotlb_sync_map = riscv_iommu_iotlb_sync_map,
> .flush_iotlb_all = riscv_iommu_flush_iotlb_all,
> + .enable_nesting = riscv_iommu_enable_nesting,
> };
>
> static const struct iommu_ops riscv_iommu_ops = {
> diff --git a/drivers/iommu/riscv/iommu.h b/drivers/iommu/riscv/iommu.h
> index 55418a1144fb..55e5aafea5bc 100644
> --- a/drivers/iommu/riscv/iommu.h
> +++ b/drivers/iommu/riscv/iommu.h
> @@ -102,8 +102,9 @@ struct riscv_iommu_domain {
> struct riscv_iommu_device *iommu;
>
> unsigned mode; /* RIO_ATP_MODE_* enum */
> - unsigned pscid; /* RISC-V IOMMU PSCID */
> + unsigned pscid; /* RISC-V IOMMU PSCID / GSCID */
> ioasid_t pasid; /* IOMMU_DOMAIN_SVA: Cached PASID */
> + bool g_stage; /* 2nd stage translation domain */
>
> pgd_t *pgd_root; /* page table root pointer */
> };
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