From: Julien Grall <julien@xen.org>
To: xen-devel@lists.xenproject.org
Cc: Wei.Chen@arm.com, Henry.Wang@arm.com, Penny.Zheng@arm.com,
Bertrand.Marquis@arm.com, Julien Grall <jgrall@amazon.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Julien Grall <julien@xen.org>,
Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: [PATCH RFCv2 05/15] xen/arm: mm: Avoid flushing the TLBs when mapping are inserted
Date: Sun, 25 Apr 2021 21:13:08 +0100 [thread overview]
Message-ID: <20210425201318.15447-6-julien@xen.org> (raw)
In-Reply-To: <20210425201318.15447-1-julien@xen.org>
From: Julien Grall <jgrall@amazon.com>
Currently, the function xen_pt_update() will flush the TLBs even when
the mappings are inserted. This is a bit wasteful because we don't
allow mapping replacement. Even if we were, the flush would need to
happen earlier because mapping replacement should use Break-Before-Make
when updating the entry.
A single call to xen_pt_update() can perform a single action. IOW, it
is not possible to, for instance, mix inserting and removing mappings.
Therefore, we can use `flags` to determine what action is performed.
This change will be particularly help to limit the impact of switching
boot time mapping to use xen_pt_update().
Signed-off-by: Julien Grall <jgrall@amazon.com>
---
Changes in v2:
- New patch
---
xen/arch/arm/mm.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 8ebb36899314..1fe52b3af722 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1101,7 +1101,13 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int level,
/* We should be here with a valid MFN. */
ASSERT(!mfn_eq(mfn, INVALID_MFN));
- /* We don't allow replacing any valid entry. */
+ /*
+ * We don't allow replacing any valid entry.
+ *
+ * Note that the function xen_pt_update() relies on this
+ * assumption and will skip the TLB flush. The function will need
+ * to be updated if the check is relaxed.
+ */
if ( lpae_is_valid(entry) )
{
if ( lpae_is_mapping(entry, level) )
@@ -1333,11 +1339,16 @@ static int xen_pt_update(unsigned long virt,
}
/*
- * Flush the TLBs even in case of failure because we may have
+ * The TLBs flush can be safely skipped when a mapping is inserted
+ * as we don't allow mapping replacement (see xen_pt_check_entry()).
+ *
+ * For all the other cases, the TLBs will be flushed unconditionally
+ * even if the mapping are failed. This is because we may have
* partially modified the PT. This will prevent any unexpected
* behavior afterwards.
*/
- flush_xen_tlb_range_va(virt, PAGE_SIZE * nr_mfns);
+ if ( !(flags & _PAGE_PRESENT) || mfn_eq(mfn, INVALID_MFN) )
+ flush_xen_tlb_range_va(virt, PAGE_SIZE * nr_mfns);
spin_unlock(&xen_pt_lock);
--
2.17.1
next prev parent reply other threads:[~2021-04-25 20:13 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-25 20:13 [PATCH RFCv2 00/15] xen/arm: mm: Remove open-coding mappings Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 01/15] xen/arm: lpae: Rename LPAE_ENTRIES_MASK_GS to LPAE_ENTRY_MASK_GS Julien Grall
2021-05-11 22:12 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 02/15] xen/arm: lpae: Use the generic helpers to defined the Xen PT helpers Julien Grall
2021-05-11 22:26 ` Stefano Stabellini
2021-05-12 14:26 ` Julien Grall
2021-05-12 21:30 ` Stefano Stabellini
2021-05-12 22:16 ` Julien Grall
2021-05-13 22:44 ` Stefano Stabellini
2021-07-03 17:32 ` Julien Grall
2021-07-13 20:53 ` Stefano Stabellini
2021-07-14 17:40 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 03/15] xen/arm: p2m: Replace level_{orders, masks} arrays with LEVEL_{ORDER, MASK} Julien Grall
2021-05-11 22:33 ` Stefano Stabellini
2021-05-12 14:39 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 04/15] xen/arm: mm: Allow other mapping size in xen_pt_update_entry() Julien Grall
2021-05-11 22:42 ` Stefano Stabellini
2021-04-25 20:13 ` Julien Grall [this message]
2021-05-11 22:51 ` [PATCH RFCv2 05/15] xen/arm: mm: Avoid flushing the TLBs when mapping are inserted Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 06/15] xen/arm: mm: Don't open-code Xen PT update in remove_early_mappings() Julien Grall
2021-05-11 22:58 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 07/15] xen/arm: mm: Re-implement early_fdt_map() using map_pages_to_xen() Julien Grall
2021-05-12 21:41 ` Stefano Stabellini
2021-05-12 22:18 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it Julien Grall
2021-05-12 22:00 ` Stefano Stabellini
2021-05-12 22:23 ` Julien Grall
2021-05-13 22:32 ` Stefano Stabellini
2021-05-13 22:59 ` Julien Grall
2021-05-14 1:04 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 09/15] xen/arm32: mm: Re-implement setup_xenheap_mappings() using map_pages_to_xen() Julien Grall
2021-05-12 22:07 ` Stefano Stabellini
2021-05-13 17:55 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 10/15] xen/arm: mm: Allocate xen page tables in domheap rather than xenheap Julien Grall
2021-05-12 22:44 ` Stefano Stabellini
2021-05-13 18:09 ` Julien Grall
2021-05-13 22:27 ` Stefano Stabellini
2021-05-15 8:48 ` Julien Grall
2021-05-18 0:37 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 11/15] xen/arm: mm: Allow page-table allocation from the boot allocator Julien Grall
2021-05-13 22:58 ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 12/15] xen/arm: add Persistent Map (PMAP) infrastructure Julien Grall
2021-04-26 9:41 ` Xia, Hongyan
2021-07-03 17:57 ` Julien Grall
2021-04-28 21:47 ` Wei Liu
2021-05-14 23:25 ` Stefano Stabellini
2021-05-15 8:54 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 13/15] xen/arm: mm: Use the PMAP helpers in xen_{,un}map_table() Julien Grall
2021-05-14 23:35 ` Stefano Stabellini
2021-05-15 9:03 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 14/15] xen/arm: mm: Rework setup_xenheap_mappings() Julien Grall
2021-05-14 23:51 ` Stefano Stabellini
2021-05-15 9:21 ` Julien Grall
2021-05-18 0:50 ` Stefano Stabellini
2022-02-12 19:16 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 15/15] xen/arm: mm: Re-implement setup_frame_table_mappings() with map_pages_to_xen() Julien Grall
2021-05-15 0:02 ` Stefano Stabellini
2021-05-15 9:25 ` Julien Grall
2021-05-18 0:51 ` Stefano Stabellini
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