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[62.83.84.125]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3557a0908e4sm14132958f8f.63.2024.05.29.01.05.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 May 2024 01:05:58 -0700 (PDT) From: Oscar Salvador X-Google-Original-From: Oscar Salvador Date: Wed, 29 May 2024 10:05:56 +0200 To: Christophe Leroy Cc: Andrew Morton , Jason Gunthorpe , Peter Xu , Michael Ellerman , Nicholas Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC PATCH v4 12/16] powerpc/e500: Encode hugepage size in PTE bits Message-ID: References: <10eae3c6815e3aba5f624af92321948e4684c95a.1716815901.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10eae3c6815e3aba5f624af92321948e4684c95a.1716815901.git.christophe.leroy@csgroup.eu> X-Rspamd-Queue-Id: DC0B1100025 X-Stat-Signature: jjnad9iaayu7c95yxt4zxz17z66eek9y X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1716969959-94429 X-HE-Meta: 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 e3rN/Oji SkXPlihdVkvK+FXaTgA5ifglfs7fw1yeLEcRLqn5VQoyN8v0H50QvOzxEkMgnGfNnT4Q3f7dypn5zsSeRi7sl2o4Z7mhcPZ1x1CB5gc86nBnB8i3NnSThDqh5xX7DOvWyQ0Rho/fKmRYHPGpjdz4hTT4hVEIKgUtkinYEG5OJoUZcqey4milqdJRfXOxEjXXCV57CR6mVOfSo6D/SyLJ+S9lvcu/+DXDh3E/mRRYTYz0uF2fvOFRNQMmoJfxRUe4sTcMp1zwghkt/3pSSacajyZ45vYwXkH+IVDb0O07BVldesD9BvAcxkqAGdbaqGblAOZYX+8sx+/QIwddVE2ssJKTgRn7sUgoz8MaYy2xocl6FtjI= 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 Mon, May 27, 2024 at 03:30:10PM +0200, Christophe Leroy wrote: > Use U0-U3 bits to encode hugepage size, more exactly page shift. > > As we start using hugepages at shift 21 (2Mbytes), substract 20 > so that it fits into 4 bits. That may change in the future if > we want to use smaller hugepages. What other shifts we can have here on e500? PUD_SHIFT? Could you please spell them out here? Or even better, > > Signed-off-by: Christophe Leroy > --- > arch/powerpc/include/asm/nohash/hugetlb-e500.h | 6 ++++++ > arch/powerpc/include/asm/nohash/pte-e500.h | 3 +++ > 2 files changed, 9 insertions(+) > > diff --git a/arch/powerpc/include/asm/nohash/hugetlb-e500.h b/arch/powerpc/include/asm/nohash/hugetlb-e500.h > index 8f04ad20e040..d8e51a3f8557 100644 > --- a/arch/powerpc/include/asm/nohash/hugetlb-e500.h > +++ b/arch/powerpc/include/asm/nohash/hugetlb-e500.h > @@ -42,4 +42,10 @@ static inline int check_and_get_huge_psize(int shift) > return shift_to_mmu_psize(shift); > } > > +static inline pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags) > +{ > + return __pte(pte_val(entry) | (_PAGE_U3 * (shift - 20))); > +} > +#define arch_make_huge_pte arch_make_huge_pte > + > #endif /* _ASM_POWERPC_NOHASH_HUGETLB_E500_H */ > diff --git a/arch/powerpc/include/asm/nohash/pte-e500.h b/arch/powerpc/include/asm/nohash/pte-e500.h > index 975facc7e38e..091e4bff1fba 100644 > --- a/arch/powerpc/include/asm/nohash/pte-e500.h > +++ b/arch/powerpc/include/asm/nohash/pte-e500.h > @@ -46,6 +46,9 @@ > #define _PAGE_NO_CACHE 0x400000 /* I: cache inhibit */ > #define _PAGE_WRITETHRU 0x800000 /* W: cache write-through */ > +#define _PAGE_HSIZE_MSK (_PAGE_U0 | _PAGE_U1 | _PAGE_U2 | _PAGE_U3) > +#define _PAGE_HSIZE_SHIFT 14 Add a comment in above explaining which P*_SHIFT we need cover with these 4bits. -- Oscar Salvador SUSE Labs