Mailing List Archive

From: Paul Durrant <pdurrant@amazon.com>

The 'legacy' functions do implicit flushing so amend the callers to do the
appropriate flushing.

Unfortunately, because of the structure of the P2M code, we cannot remove
the per-CPU 'iommu_dont_flush_iotlb' global and the optimization it
facilitates. Checking of this flag is now done only in relevant callers of
iommu_iotlb_flush(). Also, 'iommu_dont_flush_iotlb' is now declared
as bool (rather than bool_t) and setting/clearing it are no longer pointlessly
gated on is_iommu_enabled() returning true. (Arguably it is also pointless to
gate the call to iommu_iotlb_flush() on that condition - since it is a no-op
in that case - but the if clause allows the scope of a stack variable to be
restricted).

NOTE: The code in memory_add() now sets 'ret' if iommu_map() or
iommu_iotlb_flush() fails.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wl@xen.org>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: George Dunlap <george.dunlap@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Julien Grall <julien@xen.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>

v9:
- Moved check of 'iommu_dont_flush_iotlb' out of iommu_iotlb_flush() and
into callers to avoid re-introducing a problem on Arm
- Dropped Jan's R-b due to change

v6:
- Fix formatting problem in memory_add()

v5:
- Re-base
- Removed failure case on overflow of unsigned int as it is no longer
necessary

v3:
- Same as v2; elected to implement batch flushing in the grant table code as
a subsequent patch

v2:
- Shorten the diff (mainly because of a prior patch introducing automatic
flush-on-fail into iommu_map() and iommu_unmap())
---
xen/arch/x86/mm.c | 24 +++++++++++++++++-------
xen/arch/x86/mm/p2m-ept.c | 21 +++++++++++++--------
xen/arch/x86/mm/p2m-pt.c | 16 ++++++++++++----
xen/arch/x86/mm/p2m.c | 25 +++++++++++++++++--------
xen/arch/x86/x86_64/mm.c | 20 +++++++-------------
xen/common/grant_table.c | 29 ++++++++++++++++++++++-------
xen/common/memory.c | 7 +++----
xen/drivers/passthrough/iommu.c | 23 -----------------------
xen/include/xen/iommu.h | 21 +++++----------------
9 files changed, 96 insertions(+), 90 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 9447dabc50..fec8a19920 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -2441,10 +2441,16 @@ static int cleanup_page_mappings(struct page_info *page)

if ( d && unlikely(need_iommu_pt_sync(d)) && is_pv_domain(d) )
{
- int rc2 = iommu_legacy_unmap(d, _dfn(mfn), 1u << PAGE_ORDER_4K);
+ unsigned int flush_flags = 0;
+ int err;
+
+ err = iommu_unmap(d, _dfn(mfn), 1ul << PAGE_ORDER_4K, &flush_flags);
+ if ( !err && !this_cpu(iommu_dont_flush_iotlb) )
+ err = iommu_iotlb_flush(d, _dfn(mfn), 1ul << PAGE_ORDER_4K,
+ flush_flags);

if ( !rc )
- rc = rc2;
+ rc = err;
}

if ( likely(!is_special_page(page)) )
@@ -2966,14 +2972,18 @@ static int _get_page_type(struct page_info *page, unsigned long type,
if ( d && unlikely(need_iommu_pt_sync(d)) && is_pv_domain(d) )
{
mfn_t mfn = page_to_mfn(page);
+ dfn_t dfn = _dfn(mfn_x(mfn));
+ unsigned int flush_flags = 0;

if ( (x & PGT_type_mask) == PGT_writable_page )
- rc = iommu_legacy_unmap(d, _dfn(mfn_x(mfn)),
- 1ul << PAGE_ORDER_4K);
+ rc = iommu_unmap(d, dfn, 1ul << PAGE_ORDER_4K, &flush_flags);
else
- rc = iommu_legacy_map(d, _dfn(mfn_x(mfn)), mfn,
- 1ul << PAGE_ORDER_4K,
- IOMMUF_readable | IOMMUF_writable);
+ rc = iommu_map(d, dfn, mfn, 1ul << PAGE_ORDER_4K,
+ IOMMUF_readable | IOMMUF_writable, &flush_flags);
+
+ if ( !rc && !this_cpu(iommu_dont_flush_iotlb) )
+ rc = iommu_iotlb_flush(d, dfn, 1ul << PAGE_ORDER_4K,
+ flush_flags);

if ( unlikely(rc) )
{
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 12cf38f6eb..71473fd31d 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -842,15 +842,20 @@ out:
if ( rc == 0 && p2m_is_hostp2m(p2m) &&
need_modify_vtd_table )
{
- if ( iommu_use_hap_pt(d) )
- rc = iommu_iotlb_flush(d, _dfn(gfn), 1ul << order,
- (iommu_flags ? IOMMU_FLUSHF_added : 0) |
- (vtd_pte_present ? IOMMU_FLUSHF_modified
- : 0));
- else if ( need_iommu_pt_sync(d) )
+ unsigned int flush_flags = 0;
+
+ if ( need_iommu_pt_sync(d) )
rc = iommu_flags ?
- iommu_legacy_map(d, _dfn(gfn), mfn, 1ul << order, iommu_flags) :
- iommu_legacy_unmap(d, _dfn(gfn), 1ul << order);
+ iommu_map(d, _dfn(gfn), mfn, 1ul << order, iommu_flags,
+ &flush_flags) :
+ iommu_unmap(d, _dfn(gfn), 1ul << order, &flush_flags);
+ else if ( iommu_use_hap_pt(d) )
+ flush_flags =
+ (iommu_flags ? IOMMU_FLUSHF_added : 0) |
+ (vtd_pte_present ? IOMMU_FLUSHF_modified : 0);
+
+ if ( !rc && !this_cpu(iommu_dont_flush_iotlb) )
+ rc = iommu_iotlb_flush(d, _dfn(gfn), 1ul << order, flush_flags);
}

unmap_domain_page(table);
diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 3af51be78e..96cacb6748 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -678,10 +678,18 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t mfn,

if ( need_iommu_pt_sync(p2m->domain) &&
(iommu_old_flags != iommu_pte_flags || old_mfn != mfn_x(mfn)) )
- rc = iommu_pte_flags
- ? iommu_legacy_map(d, _dfn(gfn), mfn, 1ul << page_order,
- iommu_pte_flags)
- : iommu_legacy_unmap(d, _dfn(gfn), 1ul << page_order);
+ {
+ unsigned int flush_flags = 0;
+
+ rc = iommu_pte_flags ?
+ iommu_map(d, _dfn(gfn), mfn, 1ul << page_order, iommu_pte_flags,
+ &flush_flags) :
+ iommu_unmap(d, _dfn(gfn), 1ul << page_order, &flush_flags);
+
+ if ( !rc && !this_cpu(iommu_dont_flush_iotlb) )
+ rc = iommu_iotlb_flush(d, _dfn(gfn), 1ul << page_order,
+ flush_flags);
+ }

/*
* Free old intermediate tables if necessary. This has to be the
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 928344be30..01ff92862d 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1350,11 +1350,15 @@ int set_identity_p2m_entry(struct domain *d, unsigned long gfn_l,

if ( !paging_mode_translate(p2m->domain) )
{
- if ( !is_iommu_enabled(d) )
- return 0;
- return iommu_legacy_map(d, _dfn(gfn_l), _mfn(gfn_l),
- 1ul << PAGE_ORDER_4K,
- IOMMUF_readable | IOMMUF_writable);
+ unsigned int flush_flags = 0;
+
+ ret = iommu_map(d, _dfn(gfn_l), _mfn(gfn_l), 1ul << PAGE_ORDER_4K,
+ IOMMUF_readable | IOMMUF_writable, &flush_flags);
+ if ( !ret )
+ ret = iommu_iotlb_flush(d, _dfn(gfn_l), 1ul << PAGE_ORDER_4K,
+ flush_flags);
+
+ return ret;
}

gfn_lock(p2m, gfn, 0);
@@ -1442,9 +1446,14 @@ int clear_identity_p2m_entry(struct domain *d, unsigned long gfn_l)

if ( !paging_mode_translate(d) )
{
- if ( !is_iommu_enabled(d) )
- return 0;
- return iommu_legacy_unmap(d, _dfn(gfn_l), 1ul << PAGE_ORDER_4K);
+ unsigned int flush_flags = 0;
+
+ ret = iommu_unmap(d, _dfn(gfn_l), 1ul << PAGE_ORDER_4K, &flush_flags);
+ if ( !ret )
+ ret = iommu_iotlb_flush(d, _dfn(gfn_l), 1ul << PAGE_ORDER_4K,
+ flush_flags);
+
+ return ret;
}

gfn_lock(p2m, gfn, 0);
diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index bce1561e1a..7e9d165449 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1284,21 +1284,15 @@ int memory_add(unsigned long spfn, unsigned long epfn, unsigned int pxm)
!iommu_use_hap_pt(hardware_domain) &&
!need_iommu_pt_sync(hardware_domain) )
{
- for ( i = spfn; i < epfn; i++ )
- if ( iommu_legacy_map(hardware_domain, _dfn(i), _mfn(i),
- 1ul << PAGE_ORDER_4K,
- IOMMUF_readable | IOMMUF_writable) )
- break;
- if ( i != epfn )
- {
- while (i-- > old_max)
- /* If statement to satisfy __must_check. */
- if ( iommu_legacy_unmap(hardware_domain, _dfn(i),
- 1ul << PAGE_ORDER_4K) )
- continue;
+ unsigned int flush_flags = 0;
+ unsigned long n = epfn - spfn;

+ ret = iommu_map(hardware_domain, _dfn(i), _mfn(i), n,
+ IOMMUF_readable | IOMMUF_writable, &flush_flags);
+ if ( !ret )
+ ret = iommu_iotlb_flush(hardware_domain, _dfn(i), n, flush_flags);
+ if ( ret )
goto destroy_m2p;
- }
}

/* We can't revert any more */
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index a5d3ed8bda..beb6b2d40d 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -1225,11 +1225,22 @@ map_grant_ref(
kind = IOMMUF_readable;
else
kind = 0;
- if ( kind && iommu_legacy_map(ld, _dfn(mfn_x(mfn)), mfn, 1, kind) )
+
+ if ( kind )
{
- double_gt_unlock(lgt, rgt);
- rc = GNTST_general_error;
- goto undo_out;
+ dfn_t dfn = _dfn(mfn_x(mfn));
+ unsigned int flush_flags = 0;
+ int err;
+
+ err = iommu_map(ld, dfn, mfn, 1, kind, &flush_flags);
+ if ( !err )
+ err = iommu_iotlb_flush(ld, dfn, 1, flush_flags);
+ if ( err )
+ {
+ double_gt_unlock(lgt, rgt);
+ rc = GNTST_general_error;
+ goto undo_out;
+ }
}
}

@@ -1473,19 +1484,23 @@ unmap_common(
if ( rc == GNTST_okay && gnttab_need_iommu_mapping(ld) )
{
unsigned int kind;
+ dfn_t dfn = _dfn(mfn_x(op->mfn));
+ unsigned int flush_flags = 0;
int err = 0;

double_gt_lock(lgt, rgt);

kind = mapkind(lgt, rd, op->mfn);
if ( !kind )
- err = iommu_legacy_unmap(ld, _dfn(mfn_x(op->mfn)), 1);
+ err = iommu_unmap(ld, dfn, 1, &flush_flags);
else if ( !(kind & MAPKIND_WRITE) )
- err = iommu_legacy_map(ld, _dfn(mfn_x(op->mfn)), op->mfn, 1,
- IOMMUF_readable);
+ err = iommu_map(ld, dfn, op->mfn, 1, IOMMUF_readable,
+ &flush_flags);

double_gt_unlock(lgt, rgt);

+ if ( !err )
+ err = iommu_iotlb_flush(ld, dfn, 1, flush_flags);
if ( err )
rc = GNTST_general_error;
}
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 714077c1e5..fedbd9019e 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -824,8 +824,7 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
xatp->gpfn += start;
xatp->size -= start;

- if ( is_iommu_enabled(d) )
- this_cpu(iommu_dont_flush_iotlb) = 1;
+ this_cpu(iommu_dont_flush_iotlb) = true;

while ( xatp->size > done )
{
@@ -845,12 +844,12 @@ int xenmem_add_to_physmap(struct domain *d, struct xen_add_to_physmap *xatp,
}
}

+ this_cpu(iommu_dont_flush_iotlb) = false;
+
if ( is_iommu_enabled(d) )
{
int ret;

- this_cpu(iommu_dont_flush_iotlb) = 0;
-
ret = iommu_iotlb_flush(d, _dfn(xatp->idx - done), done,
IOMMU_FLUSHF_added | IOMMU_FLUSHF_modified);
if ( unlikely(ret) && rc >= 0 )
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 87f9a857bb..a9da4d2b06 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -282,18 +282,6 @@ int iommu_map(struct domain *d, dfn_t dfn, mfn_t mfn,
return rc;
}

-int iommu_legacy_map(struct domain *d, dfn_t dfn, mfn_t mfn,
- unsigned long page_count, unsigned int flags)
-{
- unsigned int flush_flags = 0;
- int rc = iommu_map(d, dfn, mfn, page_count, flags, &flush_flags);
-
- if ( !this_cpu(iommu_dont_flush_iotlb) && !rc )
- rc = iommu_iotlb_flush(d, dfn, page_count, flush_flags);
-
- return rc;
-}
-
int iommu_unmap(struct domain *d, dfn_t dfn, unsigned long page_count,
unsigned int *flush_flags)
{
@@ -338,17 +326,6 @@ int iommu_unmap(struct domain *d, dfn_t dfn, unsigned long page_count,
return rc;
}

-int iommu_legacy_unmap(struct domain *d, dfn_t dfn, unsigned long page_count)
-{
- unsigned int flush_flags = 0;
- int rc = iommu_unmap(d, dfn, page_count, &flush_flags);
-
- if ( !this_cpu(iommu_dont_flush_iotlb) && !rc )
- rc = iommu_iotlb_flush(d, dfn, page_count, flush_flags);
-
- return rc;
-}
-
int iommu_lookup_page(struct domain *d, dfn_t dfn, mfn_t *mfn,
unsigned int *flags)
{
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 13f68dc93d..a2eefe8582 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -151,16 +151,8 @@ int __must_check iommu_map(struct domain *d, dfn_t dfn, mfn_t mfn,
int __must_check iommu_unmap(struct domain *d, dfn_t dfn,
unsigned long page_count,
unsigned int *flush_flags);
-
-int __must_check iommu_legacy_map(struct domain *d, dfn_t dfn, mfn_t mfn,
- unsigned long page_count,
- unsigned int flags);
-int __must_check iommu_legacy_unmap(struct domain *d, dfn_t dfn,
- unsigned long page_count);
-
int __must_check iommu_lookup_page(struct domain *d, dfn_t dfn, mfn_t *mfn,
unsigned int *flags);
-
int __must_check iommu_iotlb_flush(struct domain *d, dfn_t dfn,
unsigned long page_count,
unsigned int flush_flags);
@@ -369,15 +361,12 @@ void iommu_dev_iotlb_flush_timeout(struct domain *d, struct pci_dev *pdev);

/*
* The purpose of the iommu_dont_flush_iotlb optional cpu flag is to
- * avoid unecessary iotlb_flush in the low level IOMMU code.
- *
- * iommu_map_page/iommu_unmap_page must flush the iotlb but somethimes
- * this operation can be really expensive. This flag will be set by the
- * caller to notify the low level IOMMU code to avoid the iotlb flushes.
- * iommu_iotlb_flush/iommu_iotlb_flush_all will be explicitly called by
- * the caller.
+ * avoid unnecessary IOMMU flushing while updating the P2M.
+ * Setting the value to true will cause iommu_iotlb_flush() to return without
+ * actually performing a flush. A batch flush must therefore be done by the
+ * calling code after setting the value back to false.
*/
-DECLARE_PER_CPU(bool_t, iommu_dont_flush_iotlb);
+DECLARE_PER_CPU(bool, iommu_dont_flush_iotlb);

extern struct spinlock iommu_pt_cleanup_lock;
extern struct page_list_head iommu_pt_cleanup_list;
--
2.20.1