From: Robin Murphy <robin.murphy@arm.com>
To: Yong Wu <yong.wu@mediatek.com>
Cc: youlin.pei@mediatek.com, anan.sun@mediatek.com,
Nicolas Boichat <drinkcat@chromium.org>,
cui.zhang@mediatek.com, srv_heupstream@mediatek.com,
chao.hao@mediatek.com, edison.hsieh@mediatek.com,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org, Evan Green <evgreen@chromium.org>,
Tomasz Figa <tfiga@google.com>,
iommu@lists.linux-foundation.org,
linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 3/7] iommu/mediatek: Use gather to achieve the tlb range flush
Date: Tue, 15 Oct 2019 12:38:35 +0100 [thread overview]
Message-ID: <5d03ebcb-0cd1-a9ad-0f4e-c219e351396c@arm.com> (raw)
In-Reply-To: <1571117166.19130.83.camel@mhfsdcap03>
On 15/10/2019 06:26, Yong Wu wrote:
> On Mon, 2019-10-14 at 15:21 +0100, Robin Murphy wrote:
>> On 14/10/2019 07:38, Yong Wu wrote:
>>> Use the iommu_gather mechanism to achieve the tlb range flush.
>>> Gather the iova range in the "tlb_add_page", then flush the merged iova
>>> range in iotlb_sync.
>>>
>>> Note: If iotlb_sync comes from iommu_iotlb_gather_add_page, we have to
>>> avoid retry the lock since the spinlock have already been acquired.
>>
>> I think this could probably be even simpler - once the actual
>> register-poking is all confined to mtk_iommu_tlb_sync(), you should be
>> able get rid of the per-domain locking in map/unmap and just have a
>> single per-IOMMU lock to serialise syncs. The io-pgtable code itself
>> hasn't needed external locking for a while now.
>
> This is more simpler! Thanks very much. I will try this.
>
> The only concern is there is no lock in the iova_to_phys then, maybe use
> the new lock instead.
iova_to_phys isn't issuing any syncs, so you don't need any locking
there - if anyone calls that in a way which races against the given
address being unmapped and remapped they can't expect a meaningful
result anyway.
Robin.
>>> Suggested-by: Tomasz Figa <tfiga@chromium.org>
>>> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
>>> ---
>>> 1) This is the special case backtrace:
>>>
>>> mtk_iommu_iotlb_sync+0x50/0xa0
>>> mtk_iommu_tlb_flush_page_nosync+0x5c/0xd0
>>> __arm_v7s_unmap+0x174/0x598
>>> arm_v7s_unmap+0x30/0x48
>>> mtk_iommu_unmap+0x50/0x78
>>> __iommu_unmap+0xa4/0xf8
>>>
>>> 2) The checking "if (gather->start == ULONG_MAX) return;" also is
>>> necessary. It will happened when unmap only go to _flush_walk, then
>>> enter this tlb_sync.
>>> ---
>>> drivers/iommu/mtk_iommu.c | 29 +++++++++++++++++++++++++----
>>> drivers/iommu/mtk_iommu.h | 1 +
>>> 2 files changed, 26 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
>>> index 5f594d6..8712afc 100644
>>> --- a/drivers/iommu/mtk_iommu.c
>>> +++ b/drivers/iommu/mtk_iommu.c
>>> @@ -234,7 +234,12 @@ static void mtk_iommu_tlb_flush_page_nosync(struct iommu_iotlb_gather *gather,
>>> unsigned long iova, size_t granule,
>>> void *cookie)
>>> {
>>> - mtk_iommu_tlb_add_flush_nosync(iova, granule, granule, true, cookie);
>>> + struct mtk_iommu_data *data = cookie;
>>> + struct iommu_domain *domain = &data->m4u_dom->domain;
>>> +
>>> + data->is_in_tlb_gather_add_page = true;
>>> + iommu_iotlb_gather_add_page(domain, gather, iova, granule);
>>> + data->is_in_tlb_gather_add_page = false;
>>> }
>>>
>>> static const struct iommu_flush_ops mtk_iommu_flush_ops = {
>>> @@ -453,12 +458,28 @@ static void mtk_iommu_flush_iotlb_all(struct iommu_domain *domain)
>>> static void mtk_iommu_iotlb_sync(struct iommu_domain *domain,
>>> struct iommu_iotlb_gather *gather)
>>> {
>>> + struct mtk_iommu_data *data = mtk_iommu_get_m4u_data();
>>> struct mtk_iommu_domain *dom = to_mtk_domain(domain);
>>> + bool is_in_gather = data->is_in_tlb_gather_add_page;
>>> + size_t length = gather->end - gather->start;
>>> unsigned long flags;
>>>
>>> - spin_lock_irqsave(&dom->pgtlock, flags);
>>> - mtk_iommu_tlb_sync(mtk_iommu_get_m4u_data());
>>> - spin_unlock_irqrestore(&dom->pgtlock, flags);
>>> + if (gather->start == ULONG_MAX)
>>> + return;
>>> +
>>> + /*
>>> + * Avoid acquire the lock when it's in gather_add_page since the lock
>>> + * has already been held.
>>> + */
>>> + if (!is_in_gather)
>>> + spin_lock_irqsave(&dom->pgtlock, flags);
>>> +
>>> + mtk_iommu_tlb_add_flush_nosync(gather->start, length, gather->pgsize,
>>> + false, data);
>>> + mtk_iommu_tlb_sync(data);
>>> +
>>> + if (!is_in_gather)
>>> + spin_unlock_irqrestore(&dom->pgtlock, flags);
>>> }
>>>
>>> static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
>>> diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
>>> index fc0f16e..d29af1d 100644
>>> --- a/drivers/iommu/mtk_iommu.h
>>> +++ b/drivers/iommu/mtk_iommu.h
>>> @@ -58,6 +58,7 @@ struct mtk_iommu_data {
>>> struct iommu_group *m4u_group;
>>> bool enable_4GB;
>>> bool tlb_flush_active;
>>> + bool is_in_tlb_gather_add_page;
>>>
>>> struct iommu_device iommu;
>>> const struct mtk_iommu_plat_data *plat_data;
>>>
>
>
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2019-10-15 11:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 6:38 [PATCH v3 0/7] Improve tlb range flush Yong Wu
2019-10-14 6:38 ` [PATCH v3 1/7] iommu/mediatek: Correct the flush_iotlb_all callback Yong Wu
2019-10-14 14:06 ` Robin Murphy
2019-10-14 6:38 ` [PATCH v3 2/7] iommu/mediatek: Add pgtlock in the iotlb_sync Yong Wu
2019-10-14 6:38 ` [PATCH v3 3/7] iommu/mediatek: Use gather to achieve the tlb range flush Yong Wu
2019-10-14 14:21 ` Robin Murphy
2019-10-15 5:26 ` Yong Wu
2019-10-15 11:38 ` Robin Murphy [this message]
2019-10-14 6:38 ` [PATCH v3 4/7] iommu/mediatek: Delete the leaf in the tlb flush Yong Wu
2019-10-14 14:22 ` Robin Murphy
2019-10-15 5:25 ` Yong Wu
2019-10-15 11:24 ` Robin Murphy
2019-10-14 6:38 ` [PATCH v3 5/7] iommu/mediatek: Move the tlb_sync into tlb_flush Yong Wu
2019-10-14 6:38 ` [PATCH v3 6/7] iommu/mediatek: Use writel for TLB range invalidation Yong Wu
2019-10-14 14:04 ` Robin Murphy
2019-10-15 5:25 ` Yong Wu
2019-10-14 6:38 ` [PATCH v3 7/7] iommu/mediatek: Reduce the tlb flush timeout value Yong Wu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5d03ebcb-0cd1-a9ad-0f4e-c219e351396c@arm.com \
--to=robin.murphy@arm.com \
--cc=anan.sun@mediatek.com \
--cc=chao.hao@mediatek.com \
--cc=cui.zhang@mediatek.com \
--cc=drinkcat@chromium.org \
--cc=edison.hsieh@mediatek.com \
--cc=evgreen@chromium.org \
--cc=iommu@lists.linux-foundation.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=matthias.bgg@gmail.com \
--cc=srv_heupstream@mediatek.com \
--cc=tfiga@google.com \
--cc=will.deacon@arm.com \
--cc=yong.wu@mediatek.com \
--cc=youlin.pei@mediatek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).