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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Stat-Signature: tox79y77b93x548fgyfrus4839kssumi X-Rspam-User: X-Rspamd-Queue-Id: B5A4240006 X-HE-Tag: 1762159445-477258 X-HE-Meta: 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 lmOo1MM2 otV2Yct2oyiAXWjCm3QRdhJRIEjX9P7nSU5VvxVPqciu6vXwjWOtjN6sRzAMTTOxCA8aEZieYQ5Jlw9XCSM8A391O7e3i5hk/3r51Zs9CILOiK1uRttO4nG3powi5Ttgj4dXo6DL4Olyy6Ud9gG9kvXe0cSeo+Ajde3HBtIY20/t/dBABjpJrOZ4H0a3pNePq5LJKXU9PdyTZkOgScsN86XYjjGUS6GwXqAKCl0T8oEZj779Rot5tT/echJyrQFwqidhLNZVH/FckKrDTzJMVTcrENr6rpimI+38IsIpYQOTaeETLcJPtYhHGkQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/11/25 12:33 pm, Qi Zheng wrote: > Hi Dev, > > On 11/3/25 2:37 PM, Dev Jain wrote: >> The implementation of CONFIG_PT_RECLAIM is completely contained in >> generic >> mm code. It depends on the RCU callback which will reclaim the >> pagetables - >> there is nothing arch-specific about that. So, enable this config for >> all architectures. > > Thanks for doing this! > > But unfortunately, not all architectures call tlb_remove_ptdesc() in > __pte_free_tlb(). Some architectures directly call pte_free() to > free PTE pages (without RCU). Thanks! This was not obvious to figure out. Is there an arch bottleneck because of which they do this? I mean to say, is something stopping us from simply redirecting __pte_free_tlb to tlb_remove_ptdesc or pte_free_defer? I am looking to enable this config at least on arm64 by default, I believe it will be legal to do this at least here. > > We need to modify these architectures first, otherwise it will > lead to UAF. This approach is feasible because Hugh provides similar > support in pte_free_defer(). > > Enabling PT_RECLAIM on all architecture has always been on my > TODO list, but it's been blocked by other things. :( > > Thanks, > Qi > >> >> Signed-off-by: Dev Jain >> --- >>   arch/x86/Kconfig | 1 - >>   mm/Kconfig       | 5 +---- >>   mm/pt_reclaim.c  | 2 +- >>   3 files changed, 2 insertions(+), 6 deletions(-) >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index fa3b616af03a..5681308a5650 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -327,7 +327,6 @@ config X86 >>       select FUNCTION_ALIGNMENT_4B >>       imply IMA_SECURE_AND_OR_TRUSTED_BOOT    if EFI >>       select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE >> -    select ARCH_SUPPORTS_PT_RECLAIM        if X86_64 >>       select ARCH_SUPPORTS_SCHED_SMT        if SMP >>       select SCHED_SMT            if SMP >>       select ARCH_SUPPORTS_SCHED_CLUSTER    if SMP >> diff --git a/mm/Kconfig b/mm/Kconfig >> index 0e26f4fc8717..903c37d02555 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -1355,13 +1355,10 @@ config ARCH_HAS_USER_SHADOW_STACK >>         The architecture has hardware support for userspace shadow call >>             stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). >>   -config ARCH_SUPPORTS_PT_RECLAIM >> -    def_bool n >> - >>   config PT_RECLAIM >>       bool "reclaim empty user page table pages" >>       default y >> -    depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP >> +    depends on MMU && SMP >>       select MMU_GATHER_RCU_TABLE_FREE >>       help >>         Try to reclaim empty user page table pages in paths other >> than munmap >> diff --git a/mm/pt_reclaim.c b/mm/pt_reclaim.c >> index 7e9455a18aae..049e17f08c6a 100644 >> --- a/mm/pt_reclaim.c >> +++ b/mm/pt_reclaim.c >> @@ -1,6 +1,6 @@ >>   // SPDX-License-Identifier: GPL-2.0 >>   #include >> -#include >> +#include >>   #include >>     #include "internal.h" >