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Message-ID: <0c5ce93a-c5ff-4b09-bde4-196da505cda2@arm.com>
Date: Wed, 7 May 2025 16:39:43 +0100
From: Robin Murphy <robin.murphy@....com>
To: Rob Clark <robdclark@...il.com>, iommu@...ts.linux.dev
Cc: linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
Rob Clark <robdclark@...omium.org>, Will Deacon <will@...nel.org>,
Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...pe.ca>,
Kevin Tian <kevin.tian@...el.com>, Nicolin Chen <nicolinc@...dia.com>,
Joao Martins <joao.m.martins@...cle.com>,
"moderated list:ARM SMMU DRIVERS" <linux-arm-kernel@...ts.infradead.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] iommu/io-pgtable-arm: Add quirk to quiet WARN_ON()
On 07/05/2025 3:29 pm, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
>
> In situations where mapping/unmapping sequence can be controlled by
> userspace, attempting to map over a region that has not yet been
> unmapped is an error. But not something that should spam dmesg.
>
> Now that there is a quirk, we can also drop the selftest_running
> flag, and use the quirk instead for selftests.
Acked-by: Robin Murphy <robin.murphy@....com>
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
> Sending v2 stand-alone, since I'm not quite ready to send a new
> iteration of the full VM_BIND series. And with selftest_running
> removed, I think this patch stands on it's own. (And maybe there
> is still time to sneak this in for v6.16, removing an iommu dep
> for the VM_BIND series in v6.17?)
>
> v2: Drop selftest_running and use IO_PGTABLE_QUIRK_NO_WARN_ON for
> the selftests
>
> drivers/iommu/io-pgtable-arm.c | 27 ++++++++++++++-------------
> include/linux/io-pgtable.h | 8 ++++++++
> 2 files changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index f27965caf6a1..a535d88f8943 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -253,8 +253,6 @@ static inline bool arm_lpae_concat_mandatory(struct io_pgtable_cfg *cfg,
> (data->start_level == 1) && (oas == 40);
> }
>
> -static bool selftest_running = false;
> -
> static dma_addr_t __arm_lpae_dma_addr(void *pages)
> {
> return (dma_addr_t)virt_to_phys(pages);
> @@ -373,7 +371,7 @@ static int arm_lpae_init_pte(struct arm_lpae_io_pgtable *data,
> for (i = 0; i < num_entries; i++)
> if (iopte_leaf(ptep[i], lvl, data->iop.fmt)) {
> /* We require an unmap first */
> - WARN_ON(!selftest_running);
> + WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> return -EEXIST;
> } else if (iopte_type(ptep[i]) == ARM_LPAE_PTE_TYPE_TABLE) {
> /*
> @@ -475,7 +473,7 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
> cptep = iopte_deref(pte, data);
> } else if (pte) {
> /* We require an unmap first */
> - WARN_ON(!selftest_running);
> + WARN_ON(!(cfg->quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> return -EEXIST;
> }
>
> @@ -649,8 +647,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> unmap_idx_start = ARM_LPAE_LVL_IDX(iova, lvl, data);
> ptep += unmap_idx_start;
> pte = READ_ONCE(*ptep);
> - if (WARN_ON(!pte))
> - return 0;
> + if (!pte) {
> + WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> + return -ENOENT;
> + }
>
> /* If the size matches this level, we're in the right place */
> if (size == ARM_LPAE_BLOCK_SIZE(lvl, data)) {
> @@ -660,8 +660,10 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data,
> /* Find and handle non-leaf entries */
> for (i = 0; i < num_entries; i++) {
> pte = READ_ONCE(ptep[i]);
> - if (WARN_ON(!pte))
> + if (!pte) {
> + WARN_ON(!(data->iop.cfg.quirks & IO_PGTABLE_QUIRK_NO_WARN_ON));
> break;
> + }
>
> if (!iopte_leaf(pte, lvl, iop->fmt)) {
> __arm_lpae_clear_pte(&ptep[i], &iop->cfg, 1);
> @@ -976,7 +978,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie)
> if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS |
> IO_PGTABLE_QUIRK_ARM_TTBR1 |
> IO_PGTABLE_QUIRK_ARM_OUTER_WBWA |
> - IO_PGTABLE_QUIRK_ARM_HD))
> + IO_PGTABLE_QUIRK_ARM_HD |
> + IO_PGTABLE_QUIRK_NO_WARN_ON))
> return NULL;
>
> data = arm_lpae_alloc_pgtable(cfg);
> @@ -1079,7 +1082,8 @@ arm_64_lpae_alloc_pgtable_s2(struct io_pgtable_cfg *cfg, void *cookie)
> struct arm_lpae_io_pgtable *data;
> typeof(&cfg->arm_lpae_s2_cfg.vtcr) vtcr = &cfg->arm_lpae_s2_cfg.vtcr;
>
> - if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB))
> + if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_S2FWB |
> + IO_PGTABLE_QUIRK_NO_WARN_ON))
> return NULL;
>
> data = arm_lpae_alloc_pgtable(cfg);
> @@ -1320,7 +1324,6 @@ static void __init arm_lpae_dump_ops(struct io_pgtable_ops *ops)
> #define __FAIL(ops, i) ({ \
> WARN(1, "selftest: test failed for fmt idx %d\n", (i)); \
> arm_lpae_dump_ops(ops); \
> - selftest_running = false; \
> -EFAULT; \
> })
>
> @@ -1336,8 +1339,6 @@ static int __init arm_lpae_run_tests(struct io_pgtable_cfg *cfg)
> size_t size, mapped;
> struct io_pgtable_ops *ops;
>
> - selftest_running = true;
> -
> for (i = 0; i < ARRAY_SIZE(fmts); ++i) {
> cfg_cookie = cfg;
> ops = alloc_io_pgtable_ops(fmts[i], cfg, cfg);
> @@ -1426,7 +1427,6 @@ static int __init arm_lpae_run_tests(struct io_pgtable_cfg *cfg)
> free_io_pgtable_ops(ops);
> }
>
> - selftest_running = false;
> return 0;
> }
>
> @@ -1448,6 +1448,7 @@ static int __init arm_lpae_do_selftests(void)
> .tlb = &dummy_tlb_ops,
> .coherent_walk = true,
> .iommu_dev = &dev,
> + .quirks = IO_PGTABLE_QUIRK_NO_WARN_ON,
> };
>
> /* __arm_lpae_alloc_pages() merely needs dev_to_node() to work */
> diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> index bba2a51c87d2..639b8f4fb87d 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -88,6 +88,13 @@ struct io_pgtable_cfg {
> *
> * IO_PGTABLE_QUIRK_ARM_HD: Enables dirty tracking in stage 1 pagetable.
> * IO_PGTABLE_QUIRK_ARM_S2FWB: Use the FWB format for the MemAttrs bits
> + *
> + * IO_PGTABLE_QUIRK_NO_WARN_ON: Do not WARN_ON() on conflicting
> + * mappings, but silently return -EEXISTS. Normally an attempt
> + * to map over an existing mapping would indicate some sort of
> + * kernel bug, which would justify the WARN_ON(). But for GPU
> + * drivers, this could be under control of userspace. Which
> + * deserves an error return, but not to spam dmesg.
> */
> #define IO_PGTABLE_QUIRK_ARM_NS BIT(0)
> #define IO_PGTABLE_QUIRK_NO_PERMS BIT(1)
> @@ -97,6 +104,7 @@ struct io_pgtable_cfg {
> #define IO_PGTABLE_QUIRK_ARM_OUTER_WBWA BIT(6)
> #define IO_PGTABLE_QUIRK_ARM_HD BIT(7)
> #define IO_PGTABLE_QUIRK_ARM_S2FWB BIT(8)
> + #define IO_PGTABLE_QUIRK_NO_WARN_ON BIT(9)
> unsigned long quirks;
> unsigned long pgsize_bitmap;
> unsigned int ias;
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