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s390/mm: KVM: pv: when tearing down, try to destroy protected pages

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When ptep_get_and_clear_full is called for a mm teardown, we will now
attempt to destroy the secure pages. This will be faster than export.

In case it was not a teardown, or if for some reason the destroy page
UVC failed, we try with an export page, like before.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
Link: https://lore.kernel.org/r/20220628135619.32410-11-imbrenda@linux.ibm.com
Message-Id: <20220628135619.32410-11-imbrenda@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2022-06-28 15:56:11 +02:00 committed by Janosch Frank
parent ca2fd0609b
commit 9bf811dae4
1 changed files with 16 additions and 3 deletions
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17
arch/s390/include/asm/pgtable.h
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@ -1182,8 +1182,21 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
} else {
res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
}
/* At this point the reference through the mapping is still present */
if (mm_is_protected(mm) && pte_present(res))
/* Nothing to do */
if (!mm_is_protected(mm) || !pte_present(res))
return res;
/*
* At this point the reference through the mapping is still present.
* The notifier should have destroyed all protected vCPUs at this
* point, so the destroy should be successful.
*/
if (full && !uv_destroy_owned_page(pte_val(res) & PAGE_MASK))
return res;
/*
* If something went wrong and the page could not be destroyed, or
* if this is not a mm teardown, the slower export is used as
* fallback instead.
*/
uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
return res;
}