arm64/boot: Disable trapping of PMZR_EL0 writes to EL2grafted

__init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2.
PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in
HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host
traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The
kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU
driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a
write from EL0 reaches the trap and takes the host down without a panic
message.

Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already
does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9
bits.

Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9")
Cc: stable@vger.kernel.org
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 72 insertions, 0 deletions

diff --git a/Documentation/process/maintainer-devicetree.rst b/Documentation/process/maintainer-devicetree.rst
new file mode 100644
index 000000000..ecc3ed638
--- /dev/null
+++ b/Documentation/process/maintainer-devicetree.rst
@@ -0,0 +1,72 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================================
+Devicetree and Open Firmware Subsystem
+======================================
+
+Other Process Documents
+-----------------------
+
+Please see the documents in Documentation/devicetree/bindings/ for information
+on how to write proper Devicetree bindings and how to submit patches.
+
+Patch Review and Handling
+-------------------------
+
+Patches handled by Devicetree maintainers are processed differently depending
+on the patch type:
+
+1. Core OF driver code, e.g. drivers/of/:
+   patches are reviewed and applied by DT maintainers.
+
+2. Devicetree bindings:
+   patches are reviewed by DT maintainers, but should be applied by subsystem
+   maintainers except in certain cases.  See also *For kernel maintainers* in
+   Documentation/devicetree/bindings/submitting-patches.rst.
+
+3. DTS and drivers:
+   DT maintainers might provide comments, but review is generally not expected.
+   DTS must pass schema checks (dtbs_check) or at least do not add any
+   new warnings.
+
+Patchwork
+~~~~~~~~~
+
+Devicetree maintainers review patches using Patchwork, so the current status of
+a patch can be checked there. For typical driver submissions, Patchwork
+receives the entire patch set, but only a few patches are usually Devicetree
+bindings that are reviewed by DT maintainers.
+
+Explanation of Patchwork statuses:
+
+ - **New**: Not yet processed by the automation toolset.
+ - **Needs ACK**: Waiting for review by DT maintainers.
+ - **Handled Elsewhere**: Non-DT patch; not being reviewed here.
+ - **RFC**: Patch was likely ignored because it was an incomplete RFC.
+ - **Changes Requested**: Patch was reviewed and DT maintainers expect changes.
+ - **Accepted**: Patch was reviewed and applied by DT maintainers to their tree.
+ - **Not Applicable**: Patch was reviewed and is likely in good shape, with a
+   *Reviewed-by* or *Acked-by* tag provided, but DT maintainers expect someone
+   else to apply it.
+
+Patch Re-review and Pinging
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Due to the high volume of email traffic, Devicetree maintainers do not read
+every email they receive and instead rely on Patchwork during the review
+process. They also often skip patches that have already been reviewed.
+
+As a result, maintainers might miss:
+
+1. Questions about already reviewed patches.
+2. Pings, for example when a patch has been reviewed by DT maintainers but has
+   not been picked up by subsystem maintainers.
+
+Such cases can be addressed by:
+
+1. Pinging DT maintainers on the IRC channel.
+2. Dropping the DT maintainer’s *Acked-by* or *Reviewed-by* tag when sending a new
+   version of the patch set, together with an explanation in the patch
+   changelog describing why the tag was removed and what is expected from DT
+   maintainers.
+