From: "Tian, Kevin" <kevin.tian@intel.com>
To: Paul Durrant <paul@xen.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: Paul Durrant <pdurrant@amazon.com>, Jan Beulich <jbeulich@suse.com>
Subject: RE: [PATCH v4 06/14] iommu: flush I/O TLB if iommu_map() or iommu_unmap() fail
Date: Fri, 14 Aug 2020 06:53:17 +0000 [thread overview]
Message-ID: <MWHPR11MB16450DC48C30E2A4770B91BC8C400@MWHPR11MB1645.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20200804134209.8717-7-paul@xen.org>
> From: Paul Durrant
> Sent: Tuesday, August 4, 2020 9:42 PM
>
> From: Paul Durrant <pdurrant@amazon.com>
>
> This patch adds a full I/O TLB flush to the error paths of iommu_map() and
> iommu_unmap().
>
> Without this change callers need constructs such as:
>
> rc = iommu_map/unmap(...)
> err = iommu_flush(...)
> if ( !rc )
> rc = err;
>
> With this change, it can be simplified to:
>
> rc = iommu_map/unmap(...)
> if ( !rc )
> rc = iommu_flush(...)
>
> because, if the map or unmap fails the flush will be unnecessary. This saves
this statement is different from change in iommu_map...
> a stack variable and generally makes the call sites tidier.
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> ---
> Cc: Jan Beulich <jbeulich@suse.com>
>
> v2:
> - New in v2
> ---
> xen/drivers/passthrough/iommu.c | 28 ++++++++++++----------------
> 1 file changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/xen/drivers/passthrough/iommu.c
> b/xen/drivers/passthrough/iommu.c
> index 660dc5deb2..e2c0193a09 100644
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -274,6 +274,10 @@ int iommu_map(struct domain *d, dfn_t dfn, mfn_t
> mfn,
> break;
> }
>
> + /* Something went wrong so flush everything and clear flush flags */
> + if ( unlikely(rc) && iommu_iotlb_flush_all(d, *flush_flags) )
> + flush_flags = 0;
> +
... earlier you said flush is unnecessary if map fails. But here actually you
still need to flush everything so it's just sort of moving error-path flush
within the map function?
Thanks
Kevin
> return rc;
> }
>
> @@ -283,14 +287,8 @@ int iommu_legacy_map(struct domain *d, dfn_t dfn,
> mfn_t mfn,
> unsigned int flush_flags = 0;
> int rc = iommu_map(d, dfn, mfn, page_order, flags, &flush_flags);
>
> - if ( !this_cpu(iommu_dont_flush_iotlb) )
> - {
> - int err = iommu_iotlb_flush(d, dfn, (1u << page_order),
> - flush_flags);
> -
> - if ( !rc )
> - rc = err;
> - }
> + if ( !this_cpu(iommu_dont_flush_iotlb) && !rc )
> + rc = iommu_iotlb_flush(d, dfn, (1u << page_order), flush_flags);
>
> return rc;
> }
> @@ -330,6 +328,10 @@ int iommu_unmap(struct domain *d, dfn_t dfn,
> unsigned int page_order,
> }
> }
>
> + /* Something went wrong so flush everything and clear flush flags */
> + if ( unlikely(rc) && iommu_iotlb_flush_all(d, *flush_flags) )
> + flush_flags = 0;
> +
> return rc;
> }
>
> @@ -338,14 +340,8 @@ int iommu_legacy_unmap(struct domain *d, dfn_t
> dfn, unsigned int page_order)
> unsigned int flush_flags = 0;
> int rc = iommu_unmap(d, dfn, page_order, &flush_flags);
>
> - if ( !this_cpu(iommu_dont_flush_iotlb) )
> - {
> - int err = iommu_iotlb_flush(d, dfn, (1u << page_order),
> - flush_flags);
> -
> - if ( !rc )
> - rc = err;
> - }
> + if ( !this_cpu(iommu_dont_flush_iotlb) && ! rc )
> + rc = iommu_iotlb_flush(d, dfn, (1u << page_order), flush_flags);
>
> return rc;
> }
> --
> 2.20.1
>
next prev parent reply other threads:[~2020-08-14 6:53 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-04 13:41 [PATCH v4 00/14] IOMMU cleanup Paul Durrant
2020-08-04 13:41 ` [PATCH v4 01/14] x86/iommu: re-arrange arch_iommu to separate common fields Paul Durrant
2020-08-14 6:14 ` Tian, Kevin
2020-08-04 13:41 ` [PATCH v4 02/14] x86/iommu: add common page-table allocator Paul Durrant
2020-08-05 15:39 ` Jan Beulich
2020-08-04 13:41 ` [PATCH v4 03/14] x86/iommu: convert VT-d code to use new page table allocator Paul Durrant
2020-08-14 6:41 ` Tian, Kevin
2020-08-14 7:16 ` Durrant, Paul
2020-08-04 13:41 ` [PATCH v4 04/14] x86/iommu: convert AMD IOMMU " Paul Durrant
2020-08-04 13:42 ` [PATCH v4 05/14] iommu: remove unused iommu_ops method and tasklet Paul Durrant
2020-08-04 13:42 ` [PATCH v4 06/14] iommu: flush I/O TLB if iommu_map() or iommu_unmap() fail Paul Durrant
2020-08-05 16:06 ` Jan Beulich
2020-08-05 16:18 ` Paul Durrant
2020-08-06 11:41 ` Jan Beulich
2020-08-14 6:53 ` Tian, Kevin [this message]
2020-08-14 7:19 ` Durrant, Paul
2020-08-04 13:42 ` [PATCH v4 07/14] iommu: make map, unmap and flush all take both an order and a count Paul Durrant
2020-08-06 9:57 ` Jan Beulich
2020-08-11 11:00 ` Durrant, Paul
2020-08-14 6:57 ` Tian, Kevin
2020-08-04 13:42 ` [PATCH v4 08/14] remove remaining uses of iommu_legacy_map/unmap Paul Durrant
2020-08-06 10:28 ` Jan Beulich
2020-08-12 9:36 ` [EXTERNAL] " Paul Durrant
2020-08-04 13:42 ` [PATCH v4 09/14] common/grant_table: batch flush I/O TLB Paul Durrant
2020-08-06 11:49 ` Jan Beulich
2020-08-04 13:42 ` [PATCH v4 10/14] iommu: remove the share_p2m operation Paul Durrant
2020-08-06 12:18 ` Jan Beulich
2020-08-14 7:04 ` Tian, Kevin
2020-08-04 13:42 ` [PATCH v4 11/14] iommu: stop calling IOMMU page tables 'p2m tables' Paul Durrant
2020-08-06 12:23 ` Jan Beulich
2020-08-14 7:12 ` Tian, Kevin
2020-08-04 13:42 ` [PATCH v4 12/14] vtd: use a bit field for root_entry Paul Durrant
2020-08-06 12:34 ` Jan Beulich
2020-08-12 13:13 ` Durrant, Paul
2020-08-18 8:27 ` Jan Beulich
2020-08-14 7:17 ` Tian, Kevin
2020-08-04 13:42 ` [PATCH v4 13/14] vtd: use a bit field for context_entry Paul Durrant
2020-08-06 12:46 ` Jan Beulich
2020-08-12 13:47 ` Paul Durrant
2020-08-14 7:19 ` Tian, Kevin
2020-08-04 13:42 ` [PATCH v4 14/14] vtd: use a bit field for dma_pte Paul Durrant
2020-08-06 12:53 ` Jan Beulich
2020-08-12 13:49 ` Paul Durrant
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