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b=Me/8UH54qRnC+ERDPuiR1P7Zp2rZ/4bVI3px3v7Yb+Y9y3meIcbxCccI6W0A8KFL6 EO3/2ejVig4WM28hIiIXRwNIzdX3iekW7difUgiZNLBZQpS7vp6pw6mcqFq0g652XP vILbUPh5cG9uVP7G0KDLii2BGUi/zsnQMEMFMTNPR59ml7eA6gYZu5LmsFIwRS5NzS qJjwkS2eX3X083+Z+zZCMzeB8SDasACC1y4EOUFWMGMbByNLMZGKYCOikrJohkF32R yFFNug3+nuDwqDsS9slWoyIww/KwzjfG5JcRoqlk5rA65qllTwXs8w7YwNeyoOgZ5d f/QZxp6KlN7Dw== Date: Sun, 20 Oct 2024 11:57:27 +0300 From: Mike Rapoport To: Gregory Price Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, dan.j.williams@intel.com, ira.weiny@intel.com, david@redhat.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rafael@kernel.org, lenb@kernel.org, akpm@linux-foundation.org, alison.schofield@intel.com, Jonathan.Cameron@huawei.com, rrichter@amd.com, ytcoode@gmail.com, haibo1.xu@intel.com, dave.jiang@intel.com Subject: Re: [PATCH v2 1/3] mm/memblock: implement memblock_advise_size_order and probe functions Message-ID: References: <20241016192445.3118-1-gourry@gourry.net> <20241016192445.3118-2-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241016192445.3118-2-gourry@gourry.net> X-Stat-Signature: re15yzi6yxc83jack6ikkijixqoxw4aa X-Rspamd-Queue-Id: 756DF100005 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1729414853-805786 X-HE-Meta: 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 UGefoY1F altEBilCWYl5T0z6CnC71KX6ObOL/CwvUlOq6GykmiSFsFF1xdOpxbNj8gW3QoyHJK1p16+bltnQduNITOGe1KbN9lGaFK2mCb/CXrM8QUxnaKKS7KLG4W3RCB0dE6+40MkchFxUXIoBB1823W+2Lnshbozc/22exN5f2kB08MjbIAkvD3HvkxhAM86Io8g0tPbQy/CtfyucNqrpEnceiM6qN8UKnaSHWUReT3MF5R/G6BqQwts0ZcfgIcKfx5QCOxwznw9rVF0KqRDQnp3ctixQ/cNzuFqar8NWDUpXUoXBk+rJ7ahOVFWLbc/uqAqll0ODqMtRQ/YJbkfEYbug3k+wiJ2hedy3yD0uQCGihiTX3j9MeTed1pwueZVgBODwgkAyB 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 Wed, Oct 16, 2024 at 03:24:43PM -0400, Gregory Price wrote: > Hotplug memory sources may have opinions on what the memblock size > should be - usually for alignment purposes. For example, CXL memory > extents can be as small as 256MB with a matching physical alignment. > > Implement memblock_advise_size_order for use during early init, prior > to allocator and smp init, for software to advise the system as to what > the preferred block size should be. > > The probe function is meant for arch_init code to fetch this value > once during memblock size calculation. Use of the advisement value > is arch-specific, and no guarantee is made that it will be used. I'm confused. Aren't we talking about memory blocks for hotplugable memory here? This functionality rather belongs to drivers/base/memory.c, doesn't it? > Calls to either function after probe results in -EBUSY to signal that > advisement is ignored or that memblock_get_size_bytes should be used. > > Suggested-by: Ira Weiny > Signed-off-by: Gregory Price > --- > include/linux/memblock.h | 2 ++ > mm/memblock.c | 49 ++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 51 insertions(+) > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index fc4d75c6cec3..efb1f7cfbd58 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -111,6 +111,8 @@ static inline void memblock_discard(void) {} > #endif > > void memblock_allow_resize(void); > +int memblock_advise_size_order(int order); > +int memblock_probe_size_order(void); > int memblock_add_node(phys_addr_t base, phys_addr_t size, int nid, > enum memblock_flags flags); > int memblock_add(phys_addr_t base, phys_addr_t size); > diff --git a/mm/memblock.c b/mm/memblock.c > index 3b9dc2d89b8a..e0bdba011564 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -2009,6 +2009,55 @@ void __init memblock_allow_resize(void) > memblock_can_resize = 1; > } > > +/* > + * @order: bit-order describing the preferred minimum block size > + * > + * Intended for use by early-boot software prior to smp and allocator init to > + * advise the architecture what the minimum block size should be. Should only > + * be called during arch init before allocator and smp init. > + * > + * This value can only decrease after it has been initially set, the intention > + * is to identify the smallest supported alignment across all opinions. > + * > + * Use of this advisement value is arch-specific. > + * > + * Returns: 0 on success, -EINVAL if order is <=0, and -EBUSY if already probed > + */ > +static int memblock_sz_order; > +#define MEMBLOCK_SZO_PROBED (-1) > +int memblock_advise_size_order(int order) > +{ > + if (order <= 0) > + return -EINVAL; > + > + if (memblock_sz_order == MEMBLOCK_SZO_PROBED) > + return -EBUSY; > + > + if (memblock_sz_order) > + memblock_sz_order = min(order, memblock_sz_order); > + else > + memblock_sz_order = order; > + > + return 0; > +} > + > +/* > + * memblock_probe_size_order is intended for arch init code to probe one time, > + * for a suggested memory block size. After the first call, the result will > + * always be -EBUSY. A late user should call memory_block_size_bytes instead to > + * determine the actual block size in use. > + * > + * Should only be called during arch init prior to allocator and smp init. > + * > + * Returns: block size order, 0 if never set, or -EBUSY if previously probed. > + */ > +int memblock_probe_size_order(void) > +{ > + int rv = xchg(&memblock_sz_order, -1); > + > + return (rv == -1) ? -EBUSY : rv; > +} > + > static int __init early_memblock(char *p) > { > if (p && strstr(p, "debug")) > -- > 2.43.0 > -- Sincerely yours, Mike.