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Peter Anvin" , "Rafael J. Wysocki" , Ryan Roberts , Sven Schnelle , Thomas Gleixner , Uladzislau Rezki , Vasily Gorbik , WANG Xuerui , Will Deacon , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, loongarch@lists.linux.dev, yosry@kernel.org Subject: Re: [PATCH 6/6] Revert "arch: introduce set_direct_map_valid_noflush()" Message-ID: References: <20260816-execmem-set-vm-perms-v0-2-v1-0-90944a3ad43f@kernel.org> <20260816-execmem-set-vm-perms-v0-2-v1-6-90944a3ad43f@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 3319E1C0009 X-Stat-Signature: kwhm8k7kg3anfdibidbtwceabqzmf3nt X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1787123635-139526 X-HE-Meta: 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 87sS5pRt Hl20KTToOh9VAUQyRfZhO0LedEKZpJx0Aao2KMAPEtv8m8SY+eEQwptaRNPOo8PCXGIk6vN2DyJIS4oMUQWGM2jmJ81diyp7AROYxwGChX+zScCsHsmiaiDjojNyf2njZnFl5O7do/lTz9fsBN1Qoh9GmJ/Rsgu0ZpeRZumMWvCIx2aqC55G5W7ky9BvXhhd1LyOdEQLYXb5rCA0FKnT0x38ogiYpCQKN4nY7ctSSciIAc2acdb7rimHB/XfgcfkOFBQPXcPphMPYsuRh1w4/JmwSdyMlnFlRJG4/szdGwQ60d+VgINLs6YzQP6qxTHtvMrCNZCaTU4LSTUY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 17, 2026 at 05:14:19PM +0200, Brendan Jackman wrote: > On Sun Aug 16, 2026 at 12:59 PM CEST, Mike Rapoport (Microsoft) wrote: > > Commit 0c6378a71574 ("arch: introduce set_direct_map_valid_noflush()") > > added set_direct_map_valid_noflush() to allow updating the direct map > > for a physically contiguous range in execmem. > > > > As Brendan recently pointed out [1], this API is confusing because on > > arm64 it means that is sets VALID bit in ptes, while on other > > architectures it is an analog of set_direct_map_default_noflush(). > > > > The only user of set_direct_map_valid_noflush() was execmem's ROX cache > > freeing path and it was switched to utilize VM_FLUSH_RESET_PERMS for > > resetting permissions of the direct map alias. > > > > With the last user gone and with set_direct_map_{invalid,default}_noflush() > > accepting number of pages as a parameter, set_direct_map_valid_noflush() > > become a copy of set_memory_valid() on arm64 and a duplicate of > > set_direct_map_{invalid,default}_noflush() on other architecture, it is > > safe to remove set_direct_map_valid_noflush(). > > > > Also drop a stale comment in arm64::__kernel_map_pages() that Linus > > bothered to add when merging changes containing set_direct_map_valid_noflush() > > to his tree. > > > > This reverts commit 0c6378a71574daa6cd1534ad42a956e3262756c7. > > > > [1] https://lore.kernel.org/all/DJ69RCVRBO0Y.3JCYSW50IC4RC@linux.dev > > > > Signed-off-by: Mike Rapoport (Microsoft) > > So basically the big issue here is specifically that > set_direct_map_valid_noflush(..., true) is special on arm64 and not x86. More precisely arm64 differers from all the rest. > And we fix that by jut deleting the API. SGTM! > > The other issue I can see here is that set_direct_map_invalid_noflush() > clears RW on x86 but doesn't set RDONLY on arm64. So if you unmap > something using set_direct_map_invalid_noflush(), then map it again > using something other than set_direct_map_default_noflush(), you get > different behaviour between the archs. > > I think the answer to that is probably: doing that is a bug, i.e. > _invalid_noflush() and _default_noflush() are a pair that you have to > use together. But I haven't checked if this is currently the case. Maybe > it would still make sense to just align these fully? All set_memory + set_direct_map functions very much rely on caller to know how to use them right. There were only handful of users outside of arch/ so it was kinda sustainable. With the increased demand for those, security and whatnot, the whole bunch of set_memory functions needs some love. > Anyway, aside from all this yapping, getting rid of _valid_noflush() > seems like an unambiguous win here so thanks for the cleanup! > > Reviewed-by: Brendan Jackman -- Sincerely yours, Mike.