From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9891D33F8BA for ; Mon, 2 Mar 2026 14:42:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772462574; cv=none; b=OQc7C0uXpjNsEpjt+cs1ge+s5lw3COTymsJZlgwFbFHPKLuJIRcvBx4WoEKKL4lBW8Z2C1ndmqVjpIbp/7Stwzmwp9SnwR+1wMDksjrS+W/sNY22pPSgk8JjNNnBggeCJtn1VrHu46tDccUiiSYOR1ux6nwCXh2gdvGrGaAPg7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772462574; c=relaxed/simple; bh=nkYfdKgBk45PvScoUM0CcIRIwDipeph3T0KP1dByIlc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OXTVby6Zh3KRC4SH40gu1sjgJBNyDID6tJc0IggnCSBobzYfkA4hNs1kvkEGLnOw9KnZ/aDPHa3KalS3zfytzX4eD5nqt8S0xqIXNCIwBml464YMlIINkT2EDACENkt69HLlS+S0Hil2RNDF4F4GFVHmvjb9noQLBGEJSPUtPCo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 829D81477; Mon, 2 Mar 2026 06:42:44 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A9BBA3F694; Mon, 2 Mar 2026 06:42:48 -0800 (PST) Date: Mon, 2 Mar 2026 14:42:45 +0000 From: Mark Rutland To: Ryan Roberts Cc: Will Deacon , Ard Biesheuvel , Catalin Marinas , Linus Torvalds , Oliver Upton , Marc Zyngier , Dev Jain , Linu Cherian , Jonathan Cameron , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 13/13] arm64: mm: Provide level hint for flush_tlb_page() Message-ID: References: <20260302135602.3716920-1-ryan.roberts@arm.com> <20260302135602.3716920-14-ryan.roberts@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260302135602.3716920-14-ryan.roberts@arm.com> Hi Ryan, On Mon, Mar 02, 2026 at 01:56:00PM +0000, Ryan Roberts wrote: > Previously tlb invalidations issued by __flush_tlb_page() did not > contain a level hint. But the function is clearly only ever targeting > level 3 tlb entries and its documentation agrees: > > | this operation only invalidates a single, last-level page-table > | entry and therefore does not affect any walk-caches FWIW, I'd have read "last-level" as synonymous with "leaf" (i.e. a Page or Block entry, which is the last level of walk) rather than level 3 specifically. The architecture uses the term to match the former (e.g. in the description of TLBI VALE1IS). If we're tightening up __flush_tlb_page(), I think it'd be worth either updating the comment to explicitly note that this only applies to level 3 entries, OR update the comment+name to say it applies to leaf entries, and have it take a level parameter. > However, it turns out that the function was actually being used to > invalidate a level 2 mapping via flush_tlb_fix_spurious_fault_pmd(). > The bug was benign because the level hint was not set so the HW would > still invalidate the PMD mapping, and also because the TLBF_NONOTIFY > flag was set, the bounds of the mapping were never used for anything > else. I suspect (as above) that the current usage was intentional, legitimate usage, just poorly documented. > Now that we have the new and improved range-invalidation API, it is > trival to fix flush_tlb_fix_spurious_fault_pmd() to explicitly flush the > whole range (locally, without notification and last level only). So > let's do that, and then update __flush_tlb_page() to hint level 3. Do we never use __flush_tlb_page() to manipulate a level 1 block mapping? I'd have expected we did the same lazy invalidation for permission relazation there, but if that's not the case, then this seems fine in principle. > Reviewed-by: Linu Cherian > Signed-off-by: Ryan Roberts > --- > arch/arm64/include/asm/pgtable.h | 5 +++-- > arch/arm64/include/asm/tlbflush.h | 2 +- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 7039931df4622..b1a96a8f2b17e 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -103,8 +103,9 @@ static inline void arch_leave_lazy_mmu_mode(void) > #define flush_tlb_fix_spurious_fault(vma, address, ptep) \ > __flush_tlb_page(vma, address, TLBF_NOBROADCAST | TLBF_NONOTIFY) > > -#define flush_tlb_fix_spurious_fault_pmd(vma, address, pmdp) \ > - __flush_tlb_page(vma, address, TLBF_NOBROADCAST | TLBF_NONOTIFY) > +#define flush_tlb_fix_spurious_fault_pmd(vma, address, pmdp) \ > + __flush_tlb_range(vma, address, address + PMD_SIZE, PMD_SIZE, 2, \ > + TLBF_NOBROADCAST | TLBF_NONOTIFY | TLBF_NOWALKCACHE) Is there a reason to keep __flush_tlb_page(), rather than defining flush_tlb_fix_spurious_fault() in terms of __flush_tlb_range() with all the level 3 constants? Mark. > > /* > * ZERO_PAGE is a global shared page that is always zero: used > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h > index 5096ec7ab8650..958fe97b744e5 100644 > --- a/arch/arm64/include/asm/tlbflush.h > +++ b/arch/arm64/include/asm/tlbflush.h > @@ -591,7 +591,7 @@ static inline void __flush_tlb_page(struct vm_area_struct *vma, > unsigned long start = round_down(uaddr, PAGE_SIZE); > unsigned long end = start + PAGE_SIZE; > > - __do_flush_tlb_range(vma, start, end, PAGE_SIZE, TLBI_TTL_UNKNOWN, > + __do_flush_tlb_range(vma, start, end, PAGE_SIZE, 3, > TLBF_NOWALKCACHE | flags); > } > > -- > 2.43.0 >