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Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Muchun Song , Oscar Salvador , Alexander Graf , David Matlack , David Rientjes , Jason Gunthorpe , Samiullah Khawaja , Vipin Sharma , Zhu Yanjun , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [RFC PATCH 03/10] liveupdate: do early initialization before hugepages are allocated In-Reply-To: (Pasha Tatashin's message of "Tue, 23 Dec 2025 13:08:59 -0500") References: <20251206230222.853493-1-pratyush@kernel.org> <20251206230222.853493-4-pratyush@kernel.org> Date: Mon, 29 Dec 2025 22:23:06 +0100 Message-ID: <86ms317zk5.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C3FB74000E X-Stat-Signature: wtdz9938za1tj11i9nw77mdh7mqc5ixu X-Rspam-User: X-HE-Tag: 1767043396-662851 X-HE-Meta: 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 DdYkm1aJ Ayp6eyKIRNhSpXJDxQtBeT9BjMxo3CTC5BS4yIjg3llzWJisvMprJsdABpgUehBpF1Qa86f40daItgRzjCx5kIaY35RMYV/fZQdHcKeuZUfW3QwP65c8QhBlbVu4Qk3475SFht7fBMibCXES5h1JcPZPXJz+TVqFasAIaRO7MNzHOX2AFz7UzEoPFRuZaXixvJSxFkUWvPekul9c= 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 Tue, Dec 23 2025, Pasha Tatashin wrote: > On Sat, Dec 6, 2025 at 6:03=E2=80=AFPM Pratyush Yadav wrote: >> >> To support hugepage preservation using LUO, the hugetlb subsystem needs >> to get liveupdate data when it allocates the hugepages to find out how >> many pages are coming from live update. >> >> Move early LUO init from early_initcall to mm_core_init(). This is where >> gigantic hugepages are allocated on ARM64. On x86, they are allocated in >> setup_arch(), so have a call there as well. Keep track of whether the >> function was already called to avoid double-init. >> >> liveupdate_early_init() only gets the KHO subtree and validates the data >> to ensure it is valid and understood. These are read-only operations and >> do not need much from the system, so it is safe to call early in boot. >> >> Signed-off-by: Pratyush Yadav >> --- >> arch/x86/kernel/setup.c | 7 +++++++ >> include/linux/liveupdate.h | 6 ++++++ >> kernel/liveupdate/luo_core.c | 30 ++++++++++++++++++++++++++---- >> kernel/liveupdate/luo_internal.h | 2 ++ >> mm/mm_init.c | 7 +++++++ >> 5 files changed, 48 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c >> index 9bf00287c408..e2ec779afc2c 100644 >> --- a/arch/x86/kernel/setup.c >> +++ b/arch/x86/kernel/setup.c >> @@ -26,6 +26,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> >> @@ -1216,6 +1217,12 @@ void __init setup_arch(char **cmdline_p) >> >> kho_memory_init(); >> >> + /* >> + * Hugepages might be preserved from a liveupdate. Make sure it = is >> + * initialized so hugetlb can query its state. >> + */ >> + liveupdate_early_init(); >> + >> if (boot_cpu_has(X86_FEATURE_GBPAGES)) { >> hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT); >> hugetlb_bootmem_alloc(); >> diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h >> index ed81e7b31a9f..78e8c529e4e7 100644 >> --- a/include/linux/liveupdate.h >> +++ b/include/linux/liveupdate.h >> @@ -214,6 +214,8 @@ struct liveupdate_flb { >> >> #ifdef CONFIG_LIVEUPDATE >> >> +void __init liveupdate_early_init(void); >> + >> /* Return true if live update orchestrator is enabled */ >> bool liveupdate_enabled(void); >> >> @@ -233,6 +235,10 @@ int liveupdate_flb_get_outgoing(struct liveupdate_f= lb *flb, void **objp); >> >> #else /* CONFIG_LIVEUPDATE */ >> >> +static inline void liveupdate_early_init(void) >> +{ >> +} >> + >> static inline bool liveupdate_enabled(void) >> { >> return false; >> diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c >> index 7a9ef16b37d8..2c740ecad8e6 100644 >> --- a/kernel/liveupdate/luo_core.c >> +++ b/kernel/liveupdate/luo_core.c >> @@ -69,6 +69,13 @@ static struct { >> u64 liveupdate_num; >> } luo_global; >> >> +static bool __luo_early_initialized __initdata; >> + >> +bool __init luo_early_initialized(void) >> +{ >> + return __luo_early_initialized; >> +} > > I think the above is not needed, both the global variable, and a new func= tion. The function is used by liveupdate_flb_incoming_early() for sanity-checking. Since we are getting rid of that, I can drop the function too. > >> + >> static int __init early_liveupdate_param(char *buf) >> { >> return kstrtobool(buf, &luo_global.enabled); >> @@ -133,20 +140,35 @@ static int __init luo_early_startup(void) >> return err; >> } >> >> -static int __init liveupdate_early_init(void) >> +/* >> + * This should only be called after KHO FDT is known. It gets the LUO s= ubtree >> + * and does initial validation, making early boot read-only access poss= ible. >> + */ >> +void __init liveupdate_early_init(void) >> { >> int err; >> >> + /* >> + * HugeTLB needs LUO to be initialized early in boot, before gig= antic >> + * hugepages are allocated. On x86, that happens in setup_arch()= , but on >> + * ARM64 (and other architectures) that happens in mm_core_init(= ). >> + * >> + * Since the code in mm_core_init() is shared between all archit= ectures, >> + * this can lead to the init being called twice. Skip if initial= ization >> + * was already done. >> + */ >> + if (__luo_early_initialized) >> + return; >> + >> + __luo_early_initialized =3D true; > > Please, make __luo_early_initialized static local. Sure, will do. > >> + >> err =3D luo_early_startup(); >> if (err) { >> luo_global.enabled =3D false; >> luo_restore_fail("The incoming tree failed to initialize= properly [%pe], disabling live update\n", >> ERR_PTR(err)); >> } >> - >> - return err; >> } >> -early_initcall(liveupdate_early_init); >> >> /* Called during boot to create outgoing LUO fdt tree */ >> static int __init luo_fdt_setup(void) >> diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_in= ternal.h >> index 6115d6a4054d..171c54af7b38 100644 >> --- a/kernel/liveupdate/luo_internal.h >> +++ b/kernel/liveupdate/luo_internal.h >> @@ -114,6 +114,8 @@ int __init luo_flb_setup_outgoing(void *fdt); >> int __init luo_flb_setup_incoming(void *fdt); >> void luo_flb_serialize(void); >> >> +bool __init luo_early_initialized(void); >> + >> #ifdef CONFIG_LIVEUPDATE_TEST >> void liveupdate_test_register(struct liveupdate_file_handler *fh); >> void liveupdate_test_unregister(struct liveupdate_file_handler *fh); >> diff --git a/mm/mm_init.c b/mm/mm_init.c >> index 93cec06c1c8a..9a5b06a93622 100644 >> --- a/mm/mm_init.c >> +++ b/mm/mm_init.c >> @@ -31,6 +31,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include "internal.h" >> #include "slab.h" >> @@ -2681,6 +2682,12 @@ void __init mm_core_init(void) >> arch_mm_preinit(); >> >> kho_memory_init(); >> + /* >> + * Hugepages might be preserved from a liveupdate. Make sure it = is >> + * initialized so hugetlb can query its state. >> + */ >> + liveupdate_early_init(); >> + >> hugetlb_bootmem_alloc(); >> >> /* Initializations relying on SMP setup */ >> -- >> 2.43.0 >> --=20 Regards, Pratyush Yadav