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powerpc/vas: Don't set uses_vas for kernel windows 

cp_abort is only required for user windows, because kernel context
must not be preempted between a copy/paste pair.

Without this patch, the init task gets used_vas set when it runs the
nx842_powernv_init initcall, which opens windows for kernel usage.

used_vas is then never cleared anywhere, so it gets propagated into
all other tasks. It's a property of the address space, so it should
really be cleared when a new mm is created (or in dup_mmap if the
mmaps are marked as VM_DONTCOPY). For now we seem to have no such
driver, so leave that for another patch.

Fixes: 6c8e6bb2a5 ("powerpc/vas: Add support for user receive window")
Cc: stable@vger.kernel.org # v4.15+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2018-02-08 19:18:38 +10:00 committed by Michael Ellerman
parent c9dccf1d07
commit b00b628986
1 changed files with 8 additions and 8 deletions
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16
arch/powerpc/platforms/powernv/vas-window.c
View File

@ -1063,16 +1063,16 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
rc = PTR_ERR(txwin->paste_kaddr);
goto free_window;
}
} else {
/*
* A user mapping must ensure that context switch issues
* CP_ABORT for this thread.
*/
rc = set_thread_uses_vas();
if (rc)
goto free_window;
}
/*
* Now that we have a send window, ensure context switch issues
* CP_ABORT for this thread.
*/
rc = -EINVAL;
if (set_thread_uses_vas() < 0)
goto free_window;
set_vinst_win(vinst, txwin);
return txwin;