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Thu, 12 Nov 2026 07:00:23 +0000 X-Mizu-Trace-ID: 5f9d5e168c7f5611 X-Migadu-Flow: FLOW_OUT Message-ID: <4ad546a2-66c5-4b74-a221-d9e8c1006c73@linux.dev> Date: Thu, 12 Nov 2026 15:01:48 +0800 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 6/9] mm/vmalloc: only flush the cache after the vmap succeeded To: Suren Baghdasaryan Cc: Uladzislau Rezki , Dev Jain , Andrew Morton , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Dennis Zhou , Tejun Heo , Christoph Lameter , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Sashiko References: <20261110112546.261415-1-hao.ge@linux.dev> <20261110112546.261415-7-hao.ge@linux.dev> Content-Language: en-US From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 2026/11/12 08:30, Suren Baghdasaryan wrote: > On Tue, Nov 10, 2026 at 11:25 AM Hao Ge wrote: >> >> vmap_page_range() and __vmap_pages_range() call flush_cache_vmap() > > New vmap_pages_range_batched() function has the same issue, so needs fixing too. Ack. will do next version. > >> before they even look at the error code. A failed mapping is never >> used, so the flush is pointless at best. >> >> According to the Sashiko review it is worse than pointless on UML: >> flush_cache_vmap() there is flush_tlb_kernel_range(), which syncs the >> PTEs into the host OS. Flushing a half-installed mapping therefore >> leaves host mappings behind for a range that was just freed again. >> >> Only flush when the mapping, and for vmap_page_range() also the KMSAN >> metadata, is fully set up. >> >> Reported-by: Sashiko >> Signed-off-by: Hao Ge >> --- >> mm/vmalloc.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index 0565cbfe325c..3f98056f8c7e 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -369,10 +369,12 @@ int vmap_page_range(unsigned long addr, unsigned long end, >> >> err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot), >> ioremap_max_page_shift); >> - flush_cache_vmap(addr, end); >> if (!err) >> err = kmsan_ioremap_page_range(addr, end, phys_addr, prot, >> ioremap_max_page_shift); >> + if (!err) >> + flush_cache_vmap(addr, end); >> + >> return err; >> } >> >> @@ -758,7 +760,9 @@ static int __vmap_pages_range(unsigned long addr, unsigned long end, >> int err; >> >> err = vmap_pages_range_noflush(addr, end, prot, pages, page_shift, gfp_mask); >> - flush_cache_vmap(addr, end); >> + if (!err) >> + flush_cache_vmap(addr, end); >> + >> return err; >> } >> >> -- >> 2.25.1 >>