From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Date: Thu, 20 Feb 2020 18:19:42 +0000 Subject: Re: [PATCH kernel 5/5] vfio/spapr_tce: Advertise and allow a huge DMA windows at 4GB Message-Id: <20200220111942.2b53414a@w520.home> List-Id: References: <20200218073650.16149-1-aik@ozlabs.ru> <20200218073650.16149-6-aik@ozlabs.ru> In-Reply-To: <20200218073650.16149-6-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Alexey Kardashevskiy Cc: Alistair Popple , linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, David Gibson On Tue, 18 Feb 2020 18:36:50 +1100 Alexey Kardashevskiy wrote: > So far the only option for a big 64big DMA window was a window located > at 0x800.0000.0000.0000 (1<<59) which creates problems for devices > supporting smaller DMA masks. > > This exploits a POWER9 PHB option to allow the second DMA window to map > at 0 and advertises it with a 4GB offset to avoid overlap with > the default 32bit window. > > Signed-off-by: Alexey Kardashevskiy > --- > include/uapi/linux/vfio.h | 2 ++ > drivers/vfio/vfio_iommu_spapr_tce.c | 10 ++++++++-- > 2 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h > index 9e843a147ead..c7f89d47335a 100644 > --- a/include/uapi/linux/vfio.h > +++ b/include/uapi/linux/vfio.h > @@ -831,9 +831,11 @@ struct vfio_iommu_spapr_tce_info { > __u32 argsz; > __u32 flags; > #define VFIO_IOMMU_SPAPR_INFO_DDW (1 << 0) /* DDW supported */ > +#define VFIO_IOMMU_SPAPR_INFO_DDW_START (1 << 1) /* DDW offset */ > __u32 dma32_window_start; /* 32 bit window start (bytes) */ > __u32 dma32_window_size; /* 32 bit window size (bytes) */ > struct vfio_iommu_spapr_tce_ddw_info ddw; > + __u64 dma64_window_start; > }; > > #define VFIO_IOMMU_SPAPR_TCE_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12) > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c > index 16b3adc508db..4f22be3c4aa2 100644 > --- a/drivers/vfio/vfio_iommu_spapr_tce.c > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c > @@ -691,7 +691,7 @@ static long tce_iommu_create_window(struct tce_container *container, > container->tables[num] = tbl; > > /* Return start address assigned by platform in create_table() */ > - *start_addr = tbl->it_offset << tbl->it_page_shift; > + *start_addr = tbl->it_dmaoff << tbl->it_page_shift; > > return 0; > > @@ -842,7 +842,13 @@ static long tce_iommu_ioctl(void *iommu_data, > info.ddw.levels = table_group->max_levels; > } > > - ddwsz = offsetofend(struct vfio_iommu_spapr_tce_info, ddw); > + ddwsz = offsetofend(struct vfio_iommu_spapr_tce_info, > + dma64_window_start); This breaks existing users, now they no longer get the ddw struct unless their argsz also includes the new dma64 window field. > + > + if (info.argsz >= ddwsz) { > + info.flags |= VFIO_IOMMU_SPAPR_INFO_DDW_START; > + info.dma64_window_start = table_group->tce64_start; > + } This is inconsistent with ddw where we set the flag regardless of argsz, but obviously only provide the field to the user if they've provided room for it. Thanks, Alex > > if (info.argsz >= ddwsz) > minsz = ddwsz;