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Date: Thu, 13 Jun 2024 13:15:27 +0200
From: Greg KH <greg@...ah.com>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
Cc: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>,
stable@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
Will Deacon <will@...nel.org>, Lu Baolu <baolu.lu@...ux.intel.com>,
Tom Murphy <murphyt7@....ie>,
Saravana Kannan <saravanak@...gle.com>,
Joerg Roedel <jroedel@...e.de>, kernel-team@...roid.com,
iommu@...ts.linux-foundation.org, iommu@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5.15.y] iommu/dma: Trace bounce buffer usage when mapping
buffers
On Thu, Jun 13, 2024 at 04:01:01PM +0530, Bibek Kumar Patro wrote:
> On Mon, Jan 22, 2024 at 12:37:54PM -0800, Isaac J. Manjarres wrote:
> > When commit 82612d66d51d ("iommu: Allow the dma-iommu api to
> > use bounce buffers") was introduced, it did not add the logic
> > for tracing the bounce buffer usage from iommu_dma_map_page().
> >
> > All of the users of swiotlb_tbl_map_single() trace their bounce
> > buffer usage, except iommu_dma_map_page(). This makes it difficult
> > to track SWIOTLB usage from that function. Thus, trace bounce buffer
> > usage from iommu_dma_map_page().
> >
> > Fixes: 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers")
> > Cc: stable@...r.kernel.org # v5.15+
> > Cc: Tom Murphy <murphyt7@....ie>
> > Cc: Lu Baolu <baolu.lu@...ux.intel.com>
> > Cc: Saravana Kannan <saravanak@...gle.com>
> > Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
> > Link: https://lore.kernel.org/r/20231208234141.2356157-1-isaacmanjarres@google.com
> > Signed-off-by: Joerg Roedel <jroedel@...e.de>
> > (cherry picked from commit a63c357b9fd56ad5fe64616f5b22835252c6a76a)
> > Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
> > ---
> > drivers/iommu/dma-iommu.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index 48c6f7ff4aef..8cd63e6ccd2c 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -25,6 +25,7 @@
> > #include <linux/vmalloc.h>
> > #include <linux/crash_dump.h>
> > #include <linux/dma-direct.h>
> > +#include <trace/events/swiotlb.h>
> >
> > struct iommu_dma_msi_page {
> > struct list_head list;
> > @@ -817,6 +818,8 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> > void *padding_start;
> > size_t padding_size, aligned_size;
> >
> > + trace_swiotlb_bounced(dev, phys, size, swiotlb_force);
> > +
>
> Hi, this backported patch trying to access swiotlb_force variable is
> causing a build conflict where CONFIG_SWIOTLB is not enabled.
>
> In file included from kernel/drivers/iommu/dma-iommu.c:28:
> kernel/include/trace/events/swiotlb.h:15:9: error: declaration of 'enum SWIOTLB_NO_FORCE' will not be visible outside of this function [-Werror,-Wvisibility]
> enum swiotlb_force swiotlb_force),
> ^
> kernel/include/linux/swiotlb.h:143:23: note: expanded from macro 'swiotlb_force'
> #define swiotlb_force SWIOTLB_NO_FORCE
> ^
> In file included from kernel/drivers/iommu/dma-iommu.c:28:
> kernel/include/trace/events/swiotlb.h:15:9: error: declaration of 'enum SWIOTLB_NO_FORCE' will not be visible outside of this function [-Werror,-Wvisibility]
> kernel/include/linux/swiotlb.h:143:23: note: expanded from macro 'swiotlb_force'
> #define swiotlb_force SWIOTLB_NO_FORCE
> ^
> In file included from kernel/drivers/iommu/dma-iommu.c:28:
> kernel/include/trace/events/swiotlb.h:15:9: error: declaration of 'enum SWIOTLB_NO_FORCE' will not be visible outside of this function [-Werror,-Wvisibility]
> kernel/include/linux/swiotlb.h:143:23: note: expanded from macro 'swiotlb_force'
> #define swiotlb_force SWIOTLB_NO_FORCE
> ^
> In file included from kernel/drivers/iommu/dma-iommu.c:28:
> kernel/include/trace/events/swiotlb.h:15:9: error: declaration of 'enum SWIOTLB_NO_FORCE' will not be visible outside of this function [-Werror,-Wvisibility]
> kernel/include/linux/swiotlb.h:143:23: note: expanded from macro 'swiotlb_force'
> #define swiotlb_force SWIOTLB_NO_FORCE
> ^
> kernel/drivers/iommu/dma-iommu.c:865:42: error: argument type 'enum SWIOTLB_NO_FORCE' is incomplete
> trace_swiotlb_bounced(dev, phys, size, swiotlb_force);
> ^~~~~~~~~~~~~
> kernel/include/linux/swiotlb.h:143:23: note: expanded from macro 'swiotlb_force'
> #define swiotlb_force SWIOTLB_NO_FORCE
> ^~~~~~~~~~~~~~~~
> kernel/include/trace/events/swiotlb.h:15:9: note: forward declaration of 'enum SWIOTLB_NO_FORCE'
> enum swiotlb_force swiotlb_force),
> ^
> kernel/include/linux/swiotlb.h:143:23: note: expanded from macro 'swiotlb_force'
> #define swiotlb_force SWIOTLB_NO_FORCE
>
> --------------------------------------------------------------------------------------------------------------------------------------------------
>
> I have a simple proposed fix which can resolve this compile time conflict when CONFIG_SWIOTLB is disabled.
>
> --- a/include/trace/events/swiotlb.h
> +++ b/include/trace/events/swiotlb.h
> @@ -7,6 +7,7 @@
>
> #include <linux/tracepoint.h>
>
> +#ifdef CONFIG_SWIOTLB
> TRACE_EVENT(swiotlb_bounced,
>
> TP_PROTO(struct device *dev,
> @@ -43,6 +44,9 @@ TRACE_EVENT(swiotlb_bounced,
> { SWIOTLB_FORCE, "FORCE" },
> { SWIOTLB_NO_FORCE, "NO_FORCE" }))
> );
> +#else
> +#define trace_swiotlb_bounced(dev, phys, size, swiotlb_force)
> +#endif /* CONFIG_SWIOTLB */
>
> #endif /* _TRACE_SWIOTLB_H */
>
>
Why not just take whatever change upstream fixes this instead of a
one-off change?
thanks
greg k-h
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