From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 38FCF644 for ; Sat, 27 May 2023 05:32:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7482C433EF for ; Sat, 27 May 2023 05:32:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685165571; bh=NgYtuftywdY9FLSkoRc9as8wdNmR5QpobqvD812H/ew=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=YZDzXUSAnP53o2yCWlLTATQDPY7oM6ePS4PJmOyH8A+2SdyjiUqRlA7ATj+trPwub 7UQFANjyzAhvoumjdwbWUhMQZhA97YH7y583/2BqaI7SnpRANDlHPPv7094TT/V4+a h2EtDMTl1/Cu9BBAJqC93X+jYVHSHwLfdrwpT1iQz6lBpsNS0Rle7L+IY/3VzQdcKx WfQ8/Tg4lC5JggZ1RB5MIPnWlsh1DbuqaQSqS6DIl7nwh9SglumQtZUqgGPWq0R6z4 xpMIdz0e4qSaWN1x/x5AhMq6Tt/Lshsbbz6Wiyc9g5YViOjEPZymmspQOBLh/6in6J q+703Tgr9Wt4w== Received: by mail-ej1-f47.google.com with SMTP id a640c23a62f3a-973bf581759so260264666b.0 for ; Fri, 26 May 2023 22:32:51 -0700 (PDT) X-Gm-Message-State: AC+VfDxq9CUKcyi8VGMDl3yBz+jED6PJaUcLy6IOoqgN8atxUyJxwcYa p3pwhKqSzW21Y3Jdnk+FDrDAPgplIRQEB9Lfew8= X-Google-Smtp-Source: ACHHUZ5pS9iHDzXG6sv+ImhknySwnRojiU77ciwfhaWLXqIPZqUdu6433Ha3MYtb1cxY+363JNB0n7ngXTWfsjXM2Hs= X-Received: by 2002:a17:907:94cf:b0:973:93d6:189f with SMTP id dn15-20020a17090794cf00b0097393d6189fmr4286386ejc.61.1685165570124; Fri, 26 May 2023 22:32:50 -0700 (PDT) Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20230524074132.10916-1-zhanghongchen@loongson.cn> In-Reply-To: <20230524074132.10916-1-zhanghongchen@loongson.cn> From: Huacai Chen Date: Sat, 27 May 2023 13:32:42 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] LoongArch: let pmd_present return true when splitting pmd To: Hongchen Zhang Cc: WANG Xuerui , Andrew Morton , Anshuman Khandual , David Hildenbrand , Mike Rapoport , Jiaxun Yang , Feiyang Chen , Qi Zheng , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, loongson-kernel@lists.loongnix.cn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi, Anshuman, Excuse me, but could you please tell me something that why commit b65399f6111b ("arm64/mm: Change THP helpers to comply with generic MM semantics") needn't be backported to 5.4LTS and 4.19LTS series. The discussion link you referred is as early as in 2018, before 4.19 released. I think this information is important for us because we want to know how to handle our 4.19-loongarch codebase. Huacai On Wed, May 24, 2023 at 3:42=E2=80=AFPM Hongchen Zhang wrote: > > when we split a pmd into ptes, pmd_present() and pmd_trans_huge() should > return true,otherwise it would be treated as a swap pmd. > As arm64 does in > commit b65399f6111b ("arm64/mm: Change THP helpers to comply with generic= MM semantics") > we add a _PAGE_PRESENT_INVALID bit for LoongArch. > > Signed-off-by: Hongchen Zhang > --- > arch/loongarch/include/asm/pgtable-bits.h | 2 ++ > arch/loongarch/include/asm/pgtable.h | 3 ++- > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/loongarch/include/asm/pgtable-bits.h b/arch/loongarch/i= nclude/asm/pgtable-bits.h > index 8b98d22a145b..a7469d28d9d0 100644 > --- a/arch/loongarch/include/asm/pgtable-bits.h > +++ b/arch/loongarch/include/asm/pgtable-bits.h > @@ -22,12 +22,14 @@ > #define _PAGE_PFN_SHIFT 12 > #define _PAGE_SWP_EXCLUSIVE_SHIFT 23 > #define _PAGE_PFN_END_SHIFT 48 > +#define _PAGE_PRESENT_INVALID_SHIFT 60 > #define _PAGE_NO_READ_SHIFT 61 > #define _PAGE_NO_EXEC_SHIFT 62 > #define _PAGE_RPLV_SHIFT 63 > > /* Used by software */ > #define _PAGE_PRESENT (_ULCAST_(1) << _PAGE_PRESENT_SHIFT) > +#define _PAGE_PRESENT_INVALID (_ULCAST_(1) << _PAGE_PRESENT_INVALID_SHI= FT) > #define _PAGE_WRITE (_ULCAST_(1) << _PAGE_WRITE_SHIFT) > #define _PAGE_ACCESSED (_ULCAST_(1) << _PAGE_ACCESSED_SHIFT) > #define _PAGE_MODIFIED (_ULCAST_(1) << _PAGE_MODIFIED_SHIFT) > diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/includ= e/asm/pgtable.h > index d28fb9dbec59..9a9f9ff9b709 100644 > --- a/arch/loongarch/include/asm/pgtable.h > +++ b/arch/loongarch/include/asm/pgtable.h > @@ -213,7 +213,7 @@ static inline int pmd_bad(pmd_t pmd) > static inline int pmd_present(pmd_t pmd) > { > if (unlikely(pmd_val(pmd) & _PAGE_HUGE)) > - return !!(pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE)= ); > + return !!(pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE = | _PAGE_PRESENT_INVALID)); > > return pmd_val(pmd) !=3D (unsigned long)invalid_pte_table; > } > @@ -558,6 +558,7 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t ne= wprot) > > static inline pmd_t pmd_mkinvalid(pmd_t pmd) > { > + pmd_val(pmd) |=3D _PAGE_PRESENT_INVALID; > pmd_val(pmd) &=3D ~(_PAGE_PRESENT | _PAGE_VALID | _PAGE_DIRTY | _= PAGE_PROTNONE); > > return pmd; > > base-commit: f1fcbaa18b28dec10281551dfe6ed3a3ed80e3d6 > -- > 2.31.1 > >