From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Ellerman Subject: Re: [PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory Date: Mon, 09 Dec 2019 16:43:17 +1100 Message-ID: <87h82aqcju.fsf@mpe.ellerman.id.au> References: <20191204123524.22919-1-rppt@kernel.org> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20191204123524.22919-1-rppt@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Mike Rapoport , linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Mike Rapoport , Christian Zigotzky , Benjamin Herrenschmidt , Christoph Hellwig , Darren Stevens , mad skateman , Nicolas Saenz Julienne , Paul Mackerras , Robin Murphy , Rob Herring List-Id: linux-arch.vger.kernel.org Mike Rapoport writes: > From: Mike Rapoport > > Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a > system has more physical memory than this limit, the swiotlb buffer is not > addressable because it is allocated from memblock using top-down mode. > > Force memblock to bottom-up mode before calling swiotlb_init() to ensure > that the swiotlb buffer is DMA-able. > > Link: https://lkml.kernel.org/r/F1EBB706-73DF-430E-9020-C214EC8ED5DA@xenosoft.de This wasn't bisected, but I thought it was a regression. Do we know what commit caused it? Was it 25078dc1f74b ("powerpc: use mm zones more sensibly") ? Or was that a red herring? cheers > Reported-by: Christian Zigotzky > Signed-off-by: Mike Rapoport > Cc: Benjamin Herrenschmidt > Cc: Christoph Hellwig > Cc: Darren Stevens > Cc: mad skateman > Cc: Michael Ellerman > Cc: Nicolas Saenz Julienne > Cc: Paul Mackerras > Cc: Robin Murphy > Cc: Rob Herring > --- > arch/powerpc/mm/mem.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c > index be941d382c8d..14c2c53e3f9e 100644 > --- a/arch/powerpc/mm/mem.c > +++ b/arch/powerpc/mm/mem.c > @@ -260,6 +260,14 @@ void __init mem_init(void) > BUILD_BUG_ON(MMU_PAGE_COUNT > 16); > > #ifdef CONFIG_SWIOTLB > + /* > + * Some platforms (e.g. 85xx) limit DMA-able memory way below > + * 4G. We force memblock to bottom-up mode to ensure that the > + * memory allocated in swiotlb_init() is DMA-able. > + * As it's the last memblock allocation, no need to reset it > + * back to to-down. > + */ > + memblock_set_bottom_up(true); > swiotlb_init(0); > #endif > > -- > 2.24.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Michael Ellerman Subject: Re: [PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory In-Reply-To: <20191204123524.22919-1-rppt@kernel.org> References: <20191204123524.22919-1-rppt@kernel.org> Date: Mon, 09 Dec 2019 16:43:17 +1100 Message-ID: <87h82aqcju.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain To: Mike Rapoport , linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Mike Rapoport , Christian Zigotzky , Benjamin Herrenschmidt , Christoph Hellwig , Darren Stevens , mad skateman , Nicolas Saenz Julienne , Paul Mackerras , Robin Murphy , Rob Herring List-ID: Message-ID: <20191209054317.Er242Q_aR-leIIXO-za1PtstY3MblqPXs-xLbX6pZxA@z> Mike Rapoport writes: > From: Mike Rapoport > > Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a > system has more physical memory than this limit, the swiotlb buffer is not > addressable because it is allocated from memblock using top-down mode. > > Force memblock to bottom-up mode before calling swiotlb_init() to ensure > that the swiotlb buffer is DMA-able. > > Link: https://lkml.kernel.org/r/F1EBB706-73DF-430E-9020-C214EC8ED5DA@xenosoft.de This wasn't bisected, but I thought it was a regression. Do we know what commit caused it? Was it 25078dc1f74b ("powerpc: use mm zones more sensibly") ? Or was that a red herring? cheers > Reported-by: Christian Zigotzky > Signed-off-by: Mike Rapoport > Cc: Benjamin Herrenschmidt > Cc: Christoph Hellwig > Cc: Darren Stevens > Cc: mad skateman > Cc: Michael Ellerman > Cc: Nicolas Saenz Julienne > Cc: Paul Mackerras > Cc: Robin Murphy > Cc: Rob Herring > --- > arch/powerpc/mm/mem.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c > index be941d382c8d..14c2c53e3f9e 100644 > --- a/arch/powerpc/mm/mem.c > +++ b/arch/powerpc/mm/mem.c > @@ -260,6 +260,14 @@ void __init mem_init(void) > BUILD_BUG_ON(MMU_PAGE_COUNT > 16); > > #ifdef CONFIG_SWIOTLB > + /* > + * Some platforms (e.g. 85xx) limit DMA-able memory way below > + * 4G. We force memblock to bottom-up mode to ensure that the > + * memory allocated in swiotlb_init() is DMA-able. > + * As it's the last memblock allocation, no need to reset it > + * back to to-down. > + */ > + memblock_set_bottom_up(true); > swiotlb_init(0); > #endif > > -- > 2.24.0