From: "Ard Biesheuvel" <ardb@kernel•org>
To: "Mike Rapoport" <rppt@kernel•org>,
"Ard Biesheuvel" <ardb+git@google•com>
Cc: linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, "Will Deacon" <will@kernel•org>,
"Catalin Marinas" <catalin.marinas@arm•com>,
"Mark Rutland" <mark.rutland@arm•com>,
"Ryan Roberts" <ryan.roberts@arm•com>,
"Anshuman Khandual" <anshuman.khandual@arm•com>,
"Liz Prucka" <lizprucka@google•com>,
"Seth Jenkins" <sethjenkins@google•com>,
"Kees Cook" <kees@kernel•org>,
"David Hildenbrand" <david@kernel•org>,
"Andrew Morton" <akpm@linux-foundation•org>,
"Jann Horn" <jannh@google•com>,
linux-mm@kvack•org, linux-hardening@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org, linux-sh@vger•kernel.org,
"Yoshinori Sato" <ysato@users•sourceforge.jp>,
"Rich Felker" <dalias@libc•org>,
"John Paul Adrian Glaubitz" <glaubitz@physik•fu-berlin.de>
Subject: Re: [PATCH v6 13/15] sh: cast away constness from the zero page when flushing it from the cache
Date: Thu, 28 May 2026 08:14:50 +0200 [thread overview]
Message-ID: <87fbe311-5657-4e36-8a33-7404980a9df6@app.fastmail.com> (raw)
In-Reply-To: <ahfWnLIwZXJvbvNg@kernel.org>
Hi Mike,
On Thu, 28 May 2026, at 07:46, Mike Rapoport wrote:
> On Tue, May 26, 2026 at 07:59:00PM +0200, Ard Biesheuvel wrote:
>> From: Ard Biesheuvel <ardb@kernel•org>
>>
>> SH performs cache maintenance on the zero page during boot, presumably
>> to ensure that any clearing of BSS that has occurred at startup is
>> visible to other CPUs and DMA devices.
>
> It flushes the cache there because before 6215d9f4470f ("arch, mm:
> consolidate empty_zero_page") empty_zero_page used was for boot parameters
> at the very early boot.
>
> I removed memset(empty_zero_page, 0, PAGE_SIZE) that was a line above but
> missed the cache flush.
>
> This whole "clear zero-page" can be removed IMO.
>
Good point.
next prev parent reply other threads:[~2026-05-28 6:58 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-26 17:58 [PATCH v6 00/15] arm64: Unmap linear alias of kernel data/bss Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 01/15] arm64: mm: Remove bogus stop condition from map_mem() loop Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 02/15] arm64: mm: Drop redundant pgd_t* argument from map_mem() Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 03/15] arm64: mm: Check for pud_/pmd_set_huge() failures on kernel mappings Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 04/15] arm64: mm: Preserve existing table mappings when mapping DRAM Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 05/15] arm64: mm: Preserve non-contiguous descriptors " Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 06/15] arm64: mm: Permit contiguous descriptors to be manipulated Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 07/15] arm64: kfence: Avoid NOMAP tricks when mapping the early pool Ard Biesheuvel
2026-05-29 8:25 ` Kevin Brodsky
2026-05-26 17:58 ` [PATCH v6 08/15] arm64: mm: Permit contiguous attribute for preliminary mappings Ard Biesheuvel
2026-05-29 8:25 ` Kevin Brodsky
2026-05-26 17:58 ` [PATCH v6 09/15] arm64: Move fixmap and kasan page tables to end of kernel image Ard Biesheuvel
2026-05-29 8:27 ` Kevin Brodsky
2026-05-29 11:19 ` Ard Biesheuvel
2026-05-29 14:42 ` Kevin Brodsky
2026-05-29 14:47 ` Ard Biesheuvel
2026-06-01 8:37 ` Kevin Brodsky
2026-06-01 8:39 ` Ard Biesheuvel
2026-05-26 17:58 ` [PATCH v6 10/15] arm64: mm: Don't abuse memblock NOMAP to check for overlaps Ard Biesheuvel
2026-05-29 8:28 ` Kevin Brodsky
2026-05-26 17:58 ` [PATCH v6 11/15] arm64: mm: Map the kernel data/bss read-only in the linear map Ard Biesheuvel
2026-05-29 8:28 ` Kevin Brodsky
2026-05-26 17:58 ` [PATCH v6 12/15] powerpc/code-patching: Avoid r/w mapping of the zero page Ard Biesheuvel
2026-05-26 17:59 ` [PATCH v6 13/15] sh: cast away constness from the zero page when flushing it from the cache Ard Biesheuvel
2026-05-27 9:31 ` Geert Uytterhoeven
2026-05-28 5:46 ` Mike Rapoport
2026-05-28 6:14 ` Ard Biesheuvel [this message]
2026-05-26 17:59 ` [PATCH v6 14/15] mm: Make empty_zero_page[] const Ard Biesheuvel
2026-05-26 17:59 ` [PATCH v6 15/15] arm64: mm: Unmap kernel data/bss entirely from the linear map Ard Biesheuvel
2026-05-29 8:29 ` Kevin Brodsky
2026-05-29 8:34 ` Ard Biesheuvel
2026-05-29 8:49 ` Kevin Brodsky
2026-05-29 11:48 ` Ard Biesheuvel
2026-05-29 8:31 ` [PATCH v6 00/15] arm64: Unmap linear alias of kernel data/bss Kevin Brodsky
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