Commit b00b6289 authored Feb 08, 2018 by Nicholas Piggin Committed by Michael Ellerman Feb 13, 2018

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: 6c8e6bb2 ("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>

parent c9dccf1d

arch/powerpc/platforms/powernv/vas-window.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -1063,15 +1063,15 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
		rc = PTR_ERR(txwin->paste_kaddr);
		goto free_window;
		}
		}

		} else {
		/*
		* Now that we have a send window, ensure context switch issues
		* A user mapping must ensure that context switch issues
		* CP_ABORT for this thread.
		*/
		rc = -EINVAL;
		if (set_thread_uses_vas() < 0)
		rc = set_thread_uses_vas();
		if (rc)
		goto free_window;
		}

		set_vinst_win(vinst, txwin);