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migration: Avoid SNP guest crash due to duplicate cpr blocker

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With aux-ram-share=off, booting an SNP guest fails with:

  ../util/error.c:68: error_setv: Assertion `*errp == NULL' failed.

This is because a CPR blocker for the guest_memfd ramblock is added
twice, once in ram_block_add_cpr_blocker because aux-ram-share=off so
rb->fd < 0, and once in ram_block_add for a specific guest_memfd blocker.

To fix, add the guest_memfd blocker iff a generic one would not be
added by ram_block_add_cpr_blocker.

Fixes: 094a3dbc55df ("migration: ram block cpr blockers")
Reported-by: Tom Lendacky <thomas.lendacky@amd.com>
Reported-by: Michael Roth <michael.roth@amd.com>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Message-ID: <1743087130-429075-1-git-send-email-steven.sistare@oracle.com>
[reword subject line]
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This commit is contained in:
Steve Sistare 2025-03-27 07:52:10 -07:00 committed by Fabiano Rosas
parent b876e721f1
commit 694b5a913d
1 changed files with 13 additions and 7 deletions
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20
system/physmem.c
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@ -158,6 +158,7 @@ static void io_mem_init(void);
static void memory_map_init(void);
static void tcg_log_global_after_sync(MemoryListener *listener);
static void tcg_commit(MemoryListener *listener);
static bool ram_is_cpr_compatible(RAMBlock *rb);
/**
* CPUAddressSpace: all the information a CPU needs about an AddressSpace
@ -1908,13 +1909,18 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
goto out_free;
}
error_setg(&new_block->cpr_blocker,
"Memory region %s uses guest_memfd, "
"which is not supported with CPR.",
memory_region_name(new_block->mr));
migrate_add_blocker_modes(&new_block->cpr_blocker, errp,
MIG_MODE_CPR_TRANSFER,
-1);
/*
* Add a specific guest_memfd blocker if a generic one would not be
* added by ram_block_add_cpr_blocker.
*/
if (ram_is_cpr_compatible(new_block)) {
error_setg(&new_block->cpr_blocker,
"Memory region %s uses guest_memfd, "
"which is not supported with CPR.",
memory_region_name(new_block->mr));
migrate_add_blocker_modes(&new_block->cpr_blocker, errp,
MIG_MODE_CPR_TRANSFER, -1);
}
}
ram_size = (new_block->offset + new_block->max_length) >> TARGET_PAGE_BITS;