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b=xpoqmgmTZPT66yheTsiYeIG4hjx8EK5I/07Aj/8MCS8I2IbU3kH4H/6ccqzVRn2G7BhH7wfQEGi+NWPi3L5OTobNJCX41+Is+5uU0sP521L4tarC1Rz25Ay/DvXc8/1GybmtbBYnbwcLJ5liX3MBpRNB1UAiGijE++yU+YRR22Q= Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DS0PR12MB9059.namprd12.prod.outlook.com (2603:10b6:8:c5::18) by LV1PR12MB999329.namprd12.prod.outlook.com (2603:10b6:408:3f8::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.522.14; Thu, 15 Oct 2026 21:42:56 +0000 Received: from DS0PR12MB9059.namprd12.prod.outlook.com ([fe80::74da:85c:3e01:6ca3]) by DS0PR12MB9059.namprd12.prod.outlook.com ([fe80::74da:85c:3e01:6ca3%4]) with mapi id 15.21.0496.021; Thu, 15 Oct 2026 21:42:56 +0000 Message-ID: <4b8a17b0-efa4-4523-b98f-70bec947ef19@amd.com> Date: Thu, 15 Oct 2026 14:42:54 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V1] accel/amdxdna: Serialize HMM range faults on one umap To: Lizhi Hou , Matthew Brost , Max Zhen Cc: ogabbay@kernel.org, quic_jhugo@quicinc.com, dri-devel@lists.freedesktop.org, mario.limonciello@amd.com, karol.wachowski@linux.intel.com, linux-kernel@vger.kernel.org, sonal.santan@amd.com References: <20261012203139.2573687-1-lizhi.hou@amd.com> <7a29937c-b591-40fc-95cf-021799ea52a7@amd.com> <160b6982-7d87-547c-9d84-cb689b35f04f@amd.com> Content-Language: en-US From: yidong Zhang In-Reply-To: <160b6982-7d87-547c-9d84-cb689b35f04f@amd.com> Content-Type: text/plain; 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Both submissions then call >>>> hmm_range_fault_unlocked_timeout() on the same struct hmm_range. That >>>> structure is not safe for concurrent callers. The calls write >>>> notifier_seq and hmm_pfns[] at the same time, so mmu_interval_read_retry() >>>> can see the other call's sequence, miss an invalidation, and clear >>>> invalid. The job is then pushed while the pages may already be gone. >>>> Give each umap its own mutex and hold it from the fault through the retry >>>> check and the store that clears invalid. notifier_lock is dropped before >>>> this mutex is taken, and the fault drops mmap_lock before notifier_lock >>>> is taken again. >>>> >>>> Fixes: aac243092b70 ("accel/amdxdna: Add command execution") >>>> Signed-off-by: Lizhi Hou >>> Reviewed-by: Max Zhen >> I was browsing dri-devel and this hmm interaction annoyed me enough to >> ask my AI to fix this and converge properly on a DRM framework: >> >> https://gitlab.freedesktop.org/mbrost/xe-kernel-driver-svn-perf-6-15-2025/-/commits/local_dev/amd_hmm_cleanup > > The patch looks clean.  I pull it on top of latest drm-misc-next and run some regression tests. It works fine too. :)  > Sure, I will wait for this fix merged then rebase my next patch on top of this fix. /David > Lizhi > >> >> Improper HMM or abuse affects the entire kernel, hence we should >> converge. >> >> Please consider the AI suggestions (last 3 patches) instead of open >> coding this. >> >> Matt >> >>>> --- >>>>    drivers/accel/amdxdna/aie2_ctx.c    | 7 ++++++- >>>>    drivers/accel/amdxdna/amdxdna_gem.c | 2 ++ >>>>    drivers/accel/amdxdna/amdxdna_gem.h | 1 + >>>>    3 files changed, 9 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/accel/amdxdna/aie2_ctx.c b/drivers/accel/amdxdna/aie2_ctx.c >>>> index d927c8c9d557..4db67a789c34 100644 >>>> --- a/drivers/accel/amdxdna/aie2_ctx.c >>>> +++ b/drivers/accel/amdxdna/aie2_ctx.c >>>> @@ -1155,19 +1155,24 @@ static int aie2_populate_range(struct amdxdna_gem_obj *abo) >>>>            return -EFAULT; >>>>        } >>>> +    mutex_lock(&mapp->lock); >>>>        ret = hmm_range_fault_unlocked_timeout(&mapp->range, timeout); >>>> -    if (ret) >>>> +    if (ret) { >>>> +        mutex_unlock(&mapp->lock); >>>>            goto put_mm; >>>> +    } >>>>        down_write(&xdna->notifier_lock); >>>>        if (mmu_interval_read_retry(&mapp->notifier, mapp->range.notifier_seq)) { >>>>            up_write(&xdna->notifier_lock); >>>> +        mutex_unlock(&mapp->lock); >>>>            amdxdna_umap_put(mapp); >>>>            mmput(mm); >>>>            goto again; >>>>        } >>>>        mapp->invalid = false; >>>>        up_write(&xdna->notifier_lock); >>>> +    mutex_unlock(&mapp->lock); >>>>        amdxdna_umap_put(mapp); >>>>        mmput(mm); >>>>        goto again; >>>> diff --git a/drivers/accel/amdxdna/amdxdna_gem.c b/drivers/accel/amdxdna/amdxdna_gem.c >>>> index f14484bc31ec..37bfa5058095 100644 >>>> --- a/drivers/accel/amdxdna/amdxdna_gem.c >>>> +++ b/drivers/accel/amdxdna/amdxdna_gem.c >>>> @@ -318,6 +318,7 @@ static void amdxdna_umap_release(struct kref *ref) >>>>        struct amdxdna_umap *mapp = container_of(ref, struct amdxdna_umap, refcnt); >>>>        mmu_interval_notifier_remove(&mapp->notifier); >>>> +    mutex_destroy(&mapp->lock); >>>>        kvfree(mapp->range.hmm_pfns); >>>>        kfree(mapp); >>>>    } >>>> @@ -402,6 +403,7 @@ static int amdxdna_hmm_register(struct amdxdna_gem_obj *abo, >>>>            goto free_pfns; >>>>        } >>>> +    mutex_init(&mapp->lock); >>>>        down_write(&xdna->notifier_lock); >>>>        if (list_empty(&abo->mem.umap_list)) >>>>            abo->mem.uva = addr; >>>> diff --git a/drivers/accel/amdxdna/amdxdna_gem.h b/drivers/accel/amdxdna/amdxdna_gem.h >>>> index 9b4aa21a37c9..456a537eb68c 100644 >>>> --- a/drivers/accel/amdxdna/amdxdna_gem.h >>>> +++ b/drivers/accel/amdxdna/amdxdna_gem.h >>>> @@ -19,6 +19,7 @@ struct amdxdna_umap { >>>>        struct kref            refcnt; >>>>        bool                invalid; >>>>        bool                unmapped; >>>> +    struct mutex            lock; /* protect range */ >>>>    }; >>>>    struct amdxdna_mem {