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[PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handl
From: |
David Hildenbrand |
Subject: |
[PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory |
Date: |
Mon, 8 Mar 2021 16:05:50 +0100 |
We can create shared anonymous memory via
"-object memory-backend-ram,share=on,..."
which is, for example, required by PVRDMA for mremap() to work.
Shared anonymous memory is weird, though. Instead of MADV_DONTNEED, we
have to use MADV_REMOVE. MADV_DONTNEED fails silently and does nothing.
Fixes: 06329ccecfa0 ("mem: add share parameter to memory-backend-ram")
Signed-off-by: David Hildenbrand <david@redhat.com>
---
softmmu/physmem.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 62ea4abbdd..2ba815fec6 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -3506,6 +3506,7 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start,
size_t length)
/* The logic here is messy;
* madvise DONTNEED fails for hugepages
* fallocate works on hugepages and shmem
+ * shared anonymous memory requires madvise REMOVE
*/
need_madvise = (rb->page_size == qemu_host_page_size);
need_fallocate = rb->fd != -1;
@@ -3539,7 +3540,11 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t
start, size_t length)
* fallocate'd away).
*/
#if defined(CONFIG_MADVISE)
- ret = madvise(host_startaddr, length, MADV_DONTNEED);
+ if (qemu_ram_is_shared(rb) && rb->fd < 0) {
+ ret = madvise(host_startaddr, length, MADV_REMOVE);
+ } else {
+ ret = madvise(host_startaddr, length, MADV_DONTNEED);
+ }
if (ret) {
ret = -errno;
error_report("ram_block_discard_range: Failed to discard range
"
--
2.29.2
- [PATCH v3 00/12] RAM_NORESERVE, MAP_NORESERVE and hostmem "reserve" property, David Hildenbrand, 2021/03/08
- [PATCH v3 01/12] softmmu/physmem: Mark shared anonymous memory RAM_SHARED, David Hildenbrand, 2021/03/08
- [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory,
David Hildenbrand <=
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, Dr. David Alan Gilbert, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, David Hildenbrand, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, Peter Xu, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, David Hildenbrand, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, David Hildenbrand, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, Peter Xu, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, David Hildenbrand, 2021/03/11
- Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, Peter Xu, 2021/03/11
Re: [PATCH v3 02/12] softmmu/physmem: Fix ram_block_discard_range() to handle shared anonymous memory, Peter Xu, 2021/03/11