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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=bJ6BTSYHKivo2/eRF9c4tWP/TAAVxpqB5Gki+6hqB70gMH9c6T0DN/7LvVp33NcYt fV1Z2JO0j2YRGDrhpnqtAy2GN69cKLeg4YLIjHpGCN+UjR/tG+22iBWPqhPA/ijEBI 8cO8DvQWcF+Nt3XHK3carG/MXQkDFh2hAqfz/P4w= Message-ID: <4ef23d65-02d2-4187-904b-9d1665d8cff5@arm.com> Date: Mon, 21 Sep 2026 16:25:25 +0100 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/6] dma: swiotlb: Centralize default pool policy selection To: "Aneesh Kumar K.V (Arm)" , iommu@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Russell King , Huacai Chen , Thomas Bogendoerfer , Jiaxun Yang , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, x86@kernel.org References: <20260921063628.362078-1-aneesh.kumar@kernel.org> <20260921063628.362078-2-aneesh.kumar@kernel.org> From: Robin Murphy Content-Language: en-GB In-Reply-To: <20260921063628.362078-2-aneesh.kumar@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21/09/2026 7:36 am, Aneesh Kumar K.V (Arm) wrote: [...] > diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c > index ba256c37bcc0..97fffa46f05a 100644 > --- a/arch/powerpc/kernel/dma-swiotlb.c > +++ b/arch/powerpc/kernel/dma-swiotlb.c > @@ -14,8 +14,10 @@ unsigned int ppc_swiotlb_flags; > > void __init swiotlb_detect_4g(void) > { > - if ((memblock_end_of_DRAM() - 1) > 0xffffffff) > + if ((memblock_end_of_DRAM() - 1) > 0xffffffff) { > ppc_swiotlb_enable = 1; Nit: Perhaps it's beyond the functional scope of this patch, but I do wonder if these _swiotlb_enable conditions become redundant and could just be replaced with "if (_swiotlb_flags != 0)" too. > + ppc_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT; > + } > } > > static int __init check_swiotlb_enabled(void) [...] > diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c > index 75cf8f6ae8cd..0cff255827ba 100644 > --- a/arch/x86/kernel/pci-dma.c > +++ b/arch/x86/kernel/pci-dma.c > @@ -44,8 +44,10 @@ static unsigned int x86_swiotlb_flags; > static void __init pci_swiotlb_detect(void) > { > /* don't initialize swiotlb if iommu=off (no_iommu=1) */ > - if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN) > + if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN) { > x86_swiotlb_enable = true; > + x86_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT; > + } > > /* > * Set swiotlb to 1 so that bounce buffers are allocated and used for > @@ -81,8 +83,10 @@ static void __init pci_xen_swiotlb_init(void) > if (!xen_swiotlb_enabled()) > return; > x86_swiotlb_enable = true; > - x86_swiotlb_flags |= SWIOTLB_ANY; > - swiotlb_init_remap(true, x86_swiotlb_flags, xen_swiotlb_fixup); > + /* Xen can use a SWIOTLB pool anywhere in directly mapped memory. */ > + x86_swiotlb_flags &= ~SWIOTLB_INIT_ADDRESSING_LIMIT; > + x86_swiotlb_flags |= SWIOTLB_INIT_REMAP | SWIOTLB_ANY; Similarly, I see how having a SWIOTLB_INIT_REMAP flag keeps swiotlb_select_pool_policy() neat, but couldn't we technically already infer that from the fact that a non-NULL remap function was passed? Nits aside, the overall change seems reasonable to me; Reviewed-by: Robin Murphy