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Sat, 06 Jun 2026 08:51:13 -0700 (PDT) Message-ID: <9ca8d72c-af36-43a4-90ab-90f13b02f4fb@gmail.com> Date: Sat, 6 Jun 2026 23:51:07 +0800 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] nvme-apple: Prevent tag collision across queues even if tag space is shared Content-Language: en-MW To: David Laight Cc: Sven Peter , Janne Grunau , Neal Gompa , Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yuriy Havrylyuk References: <20260606-prevent-tag-collision-t8015-v1-0-93ccf4eca550@gmail.com> <20260606-prevent-tag-collision-t8015-v1-2-93ccf4eca550@gmail.com> <20260606152930.6f2bf4ed@pumpkin> From: Nick Chan In-Reply-To: <20260606152930.6f2bf4ed@pumpkin> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit David Laight 於 2026/6/6 晚上10:29 寫道: > On Sat, 06 Jun 2026 21:25:26 +0800 > Nick Chan wrote: > >> From: Yuriy Havrylyuk >> >> Apple NVMe controllers require tags of pending commands to not be shared >> across admin and IO queues. However, on Apple A11 without linear SQ, it is >> not possible for either queue to skip over some tags and must go from 0 to >> the configured maximum before wrapping around. >> >> If a pending command tag is duplicated across queues, the firmware >> crashes with: "duplicate tag error for tag N", with N being the tag. >> >> Instead of partitioning the tag space, which is not possible without >> linear SQ, prevent tag collisions by keeping track of which tags are >> currently in-flight across either queues, and return BLK_STS_RESOURCE to >> temporaily block command submission when a collision would have occurred. > > I look at using the atomic64_xxx() functions rather than the bitmask ones. > The for_each_bit_set() loop is then an atmomic64_andnot() call. That does in fact simplify the loop code. However, using the atomic function complicates the apple_nvme_reserve_tag_t8015() and apple_nvme_release_tag_t8015() since those functions deal with set/clear a a bit in terms of an integer (the tag). Especially in the apple_nvme_reserve_tag_t8015() function the function body is then u64 tag_bit = BIT(nvme_tag_from_cid(cmd->common.command_id)); return !(atomic64_fetch_or(tag_bit, &anv->t8015_active_tags) & tag_bit); The function would need to explictly convert the tag to a bit, and then explictly extract the bit value after performing the atomic operation, both which of could have been done by test_and_set_bit(). So I do not see any overall benefit for using atomic_xxx() functions. Best Regards, Nick Chan > > -- David > > >> >> Cc: stable@vger.kernel.org >> Fixes: 04d8ecf37b5e ("nvme: apple: Add Apple A11 support") >> Signed-off-by: Yuriy Havrylyuk >> Co-developed-by: Nick Chan >> Signed-off-by: Nick Chan >> --- >> drivers/nvme/host/apple.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 65 insertions(+) >> >> diff --git a/drivers/nvme/host/apple.c b/drivers/nvme/host/apple.c >> index c1115e27a0d6..6354edf27225 100644 >> --- a/drivers/nvme/host/apple.c >> +++ b/drivers/nvme/host/apple.c >> @@ -203,6 +203,20 @@ struct apple_nvme { >> >> int irq; >> spinlock_t lock; >> + >> + /* >> + * Tags of pending commands must be unique across both Admin and IO >> + * queue. However, on T8015, unlike T8103, without linear submission >> + * queues, it is not possible for the either queue to skip some tags, >> + * and both queues must go from 0 to their respective configured >> + * maximum. >> + * >> + * Instead of reserving some tags for the admin queue, use a bitfield >> + * to keep track of pending commands on either queue, and temporaily >> + * block command submission by returning BLK_STS_RESOURCE until the >> + * tag is freed on the other queue. >> + */ >> + unsigned long t8015_active_tags; >> }; >> >> static_assert(sizeof(struct nvme_command) == 64); >> @@ -290,6 +304,28 @@ static void apple_nvmmu_inval(struct apple_nvme_queue *q, unsigned int tag) >> "NVMMU TCB invalidation failed\n"); >> } >> >> +static bool apple_nvme_reserve_tag_t8015(struct apple_nvme *anv, >> + struct nvme_command *cmd) >> +{ >> + u16 tag = nvme_tag_from_cid(cmd->common.command_id); >> + >> + if (WARN_ON_ONCE(tag >= BITS_PER_LONG)) >> + return false; >> + >> + return !test_and_set_bit(tag, &anv->t8015_active_tags); >> +} >> + >> +static void apple_nvme_release_tag_t8015(struct apple_nvme *anv, >> + __u16 command_id) >> +{ >> + u16 tag = nvme_tag_from_cid(command_id); >> + >> + if (WARN_ON_ONCE(tag >= BITS_PER_LONG)) >> + return; >> + >> + clear_bit(tag, &anv->t8015_active_tags); >> +} >> + >> static void apple_nvme_submit_cmd_t8015(struct apple_nvme_queue *q, >> struct nvme_command *cmd) >> { >> @@ -652,6 +688,8 @@ static inline void apple_nvme_update_cq_head(struct apple_nvme_queue *q) >> static bool apple_nvme_poll_cq(struct apple_nvme_queue *q, >> struct io_comp_batch *iob) >> { >> + struct apple_nvme *anv = queue_to_apple_nvme(q); >> + unsigned long completed_tags = 0; >> bool found = false; >> >> while (apple_nvme_cqe_pending(q)) { >> @@ -664,11 +702,26 @@ static bool apple_nvme_poll_cq(struct apple_nvme_queue *q, >> dma_rmb(); >> apple_nvme_handle_cqe(q, iob, q->cq_head); >> apple_nvme_update_cq_head(q); >> + >> + if (!anv->hw->has_lsq_nvmmu) { >> + struct nvme_completion *cqe = &q->cqes[q->cq_head]; >> + u16 tag = nvme_tag_from_cid(READ_ONCE(cqe->command_id)); >> + >> + if (!WARN_ON_ONCE(tag >= BITS_PER_LONG)) >> + __set_bit(tag, &completed_tags); >> + } >> } >> >> if (found) >> writel(q->cq_head, q->cq_db); >> >> + if (!anv->hw->has_lsq_nvmmu && completed_tags) { >> + unsigned long tag_bit; >> + >> + for_each_set_bit(tag_bit, &completed_tags, BITS_PER_LONG) >> + clear_bit(tag_bit, &anv->t8015_active_tags); >> + } >> + >> return found; >> } >> >> @@ -790,6 +843,12 @@ static blk_status_t apple_nvme_queue_rq(struct blk_mq_hw_ctx *hctx, >> if (ret) >> return ret; >> >> + if (!anv->hw->has_lsq_nvmmu && >> + !apple_nvme_reserve_tag_t8015(anv, cmnd)) { >> + ret = BLK_STS_RESOURCE; >> + goto out_free_cmd; >> + } >> + >> if (blk_rq_nr_phys_segments(req)) { >> ret = apple_nvme_map_data(anv, req, cmnd); >> if (ret) >> @@ -806,6 +865,9 @@ static blk_status_t apple_nvme_queue_rq(struct blk_mq_hw_ctx *hctx, >> return BLK_STS_OK; >> >> out_free_cmd: >> + if (!anv->hw->has_lsq_nvmmu) >> + apple_nvme_release_tag_t8015(anv, cmnd->common.command_id); >> + >> nvme_cleanup_cmd(req); >> return ret; >> } >> @@ -1165,6 +1227,9 @@ static void apple_nvme_reset_work(struct work_struct *work) >> if (ret) >> goto out; >> >> + if (!anv->hw->has_lsq_nvmmu) >> + WRITE_ONCE(anv->t8015_active_tags, 0); >> + >> dev_dbg(anv->dev, "Starting admin queue"); >> apple_nvme_init_queue(&anv->adminq); >> nvme_unquiesce_admin_queue(&anv->ctrl); >> >