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xen/x86: restrict PV Dom0 identity mapping 

When moving away RAM pages, there having been a mapping of those is not
a proper indication that instead MMIO should be mapped there. At the
point in time this effectively covers the low megabyte only. Mapping of
that is, however, the job of init_mem_mapping(). Comparing the two one
can also spot that we've been wrongly (or at least inconsistently) using
PAGE_KERNEL_IO here.

Simply zap any such mappings instead.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/038b8c02-3621-d66a-63ae-982ccf67ae88@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
This commit is contained in:
Jan Beulich 2021-09-30 14:37:19 +02:00 committed by Boris Ostrovsky
parent 344485a21d
commit 9a58b352e9
1 changed files with 3 additions and 3 deletions
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6
arch/x86/xen/setup.c
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@ -425,13 +425,13 @@ static unsigned long __init xen_set_identity_and_remap_chunk(
}
/*
* If the PFNs are currently mapped, the VA mapping also needs
* to be updated to be 1:1.
* If the PFNs are currently mapped, their VA mappings need to be
* zapped.
*/
for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++)
(void)HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn << PAGE_SHIFT),
mfn_pte(pfn, PAGE_KERNEL_IO), 0);
native_make_pte(0), 0);
return remap_pfn;
}