Re: [PATCH v5 03/17] asm-generic: pgalloc: Provide generic p4d_{alloc_one,free}

On Wed, Jan 8, 2025, at 07:57, Qi Zheng wrote:

From: Kevin Brodsky <redacted>

Four architectures currently implement 5-level pgtables: arm64,
riscv, x86 and s390. The first three have essentially the same
implementation for p4d_alloc_one() and p4d_free(), so we've got an
opportunity to reduce duplication like at the lower levels.

Provide a generic version of p4d_alloc_one() and p4d_free(), and
make use of it on those architectures.

Their implementation is the same as at PUD level, except that
p4d_free() performs a runtime check by calling mm_p4d_folded().
5-level pgtables depend on a runtime-detected hardware feature on
all supported architectures, so we might as well include this check
in the generic implementation. No runtime check is required in
p4d_alloc_one() as the top-level p4d_alloc() already does the
required check.

Signed-off-by: Kevin Brodsky <redacted>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Qi Zheng <redacted>
---
 arch/arm64/include/asm/pgalloc.h | 17 ------------
 arch/riscv/include/asm/pgalloc.h | 23 ----------------
 arch/x86/include/asm/pgalloc.h   | 18 -------------
 include/asm-generic/pgalloc.h    | 45 ++++++++++++++++++++++++++++++++
 4 files changed, 45 insertions(+), 58 deletions(-)

Acked-by: Arnd Bergmann <arnd@arndb.de> # asm-generic