| Message ID | 20200520234520.22563-2-sstabellini@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | fix swiotlb-xen for RPi4 | expand |
Hi, On 21/05/2020 00:45, Stefano Stabellini wrote: > From: Stefano Stabellini <stefano.stabellini@xilinx.com> > > It is not strictly needed. Call virt_to_phys on xen_io_tlb_start > instead. It will be useful not to have a start_dma_addr around with the > next patches. > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com> > --- > drivers/xen/swiotlb-xen.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > index a42129cba36e..b5e0492b07b9 100644 > --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -52,8 +52,6 @@ static unsigned long xen_io_tlb_nslabs; > * Quick lookup value of the bus address of the IOTLB. > */ > > -static u64 start_dma_addr; > - > /* > * Both of these functions should avoid XEN_PFN_PHYS because phys_addr_t > * can be 32bit when dma_addr_t is 64bit leading to a loss in > @@ -241,7 +239,6 @@ int __ref xen_swiotlb_init(int verbose, bool early) > m_ret = XEN_SWIOTLB_EFIXUP; > goto error; > } > - start_dma_addr = xen_virt_to_bus(xen_io_tlb_start); > if (early) { > if (swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, > verbose)) > @@ -389,7 +386,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page, > */ > trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force); > > - map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, > + map = swiotlb_tbl_map_single(dev, virt_to_phys(xen_io_tlb_start), phys, xen_virt_to_bus() is implemented as xen_phys_to_bus(virt_to_phys()). Can you explain how the two are equivalent? Cheers,
On Thu, 21 May 2020, Julien Grall wrote: > Hi, > > On 21/05/2020 00:45, Stefano Stabellini wrote: > > From: Stefano Stabellini <stefano.stabellini@xilinx.com> > > > > It is not strictly needed. Call virt_to_phys on xen_io_tlb_start > > instead. It will be useful not to have a start_dma_addr around with the > > next patches. > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com> > > --- > > drivers/xen/swiotlb-xen.c | 5 +---- > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > > index a42129cba36e..b5e0492b07b9 100644 > > --- a/drivers/xen/swiotlb-xen.c > > +++ b/drivers/xen/swiotlb-xen.c > > @@ -52,8 +52,6 @@ static unsigned long xen_io_tlb_nslabs; > > * Quick lookup value of the bus address of the IOTLB. > > */ > > -static u64 start_dma_addr; > > - > > /* > > * Both of these functions should avoid XEN_PFN_PHYS because phys_addr_t > > * can be 32bit when dma_addr_t is 64bit leading to a loss in > > @@ -241,7 +239,6 @@ int __ref xen_swiotlb_init(int verbose, bool early) > > m_ret = XEN_SWIOTLB_EFIXUP; > > goto error; > > } > > - start_dma_addr = xen_virt_to_bus(xen_io_tlb_start); > > if (early) { > > if (swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, > > verbose)) > > @@ -389,7 +386,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device > > *dev, struct page *page, > > */ > > trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force); > > - map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, > > + map = swiotlb_tbl_map_single(dev, virt_to_phys(xen_io_tlb_start), > > phys, > > xen_virt_to_bus() is implemented as xen_phys_to_bus(virt_to_phys()). Can you > explain how the two are equivalent? They are not equivalent. Looking at what swiotlb_tbl_map_single expects, and also the implementation of swiotlb_init_with_tbl, I think virt_to_phys is actually the one we want. swiotlb_tbl_map_single compares the argument with __pa(tlb) which is __pa(xen_io_tlb_start) which is virt_to_phys(xen_io_tlb_start).
Hi, On 22/05/2020 04:55, Stefano Stabellini wrote: > On Thu, 21 May 2020, Julien Grall wrote: >> Hi, >> >> On 21/05/2020 00:45, Stefano Stabellini wrote: >>> From: Stefano Stabellini <stefano.stabellini@xilinx.com> >>> >>> It is not strictly needed. Call virt_to_phys on xen_io_tlb_start >>> instead. It will be useful not to have a start_dma_addr around with the >>> next patches. >>> >>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com> >>> --- >>> drivers/xen/swiotlb-xen.c | 5 +---- >>> 1 file changed, 1 insertion(+), 4 deletions(-) >>> >>> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c >>> index a42129cba36e..b5e0492b07b9 100644 >>> --- a/drivers/xen/swiotlb-xen.c >>> +++ b/drivers/xen/swiotlb-xen.c >>> @@ -52,8 +52,6 @@ static unsigned long xen_io_tlb_nslabs; >>> * Quick lookup value of the bus address of the IOTLB. >>> */ >>> -static u64 start_dma_addr; >>> - >>> /* >>> * Both of these functions should avoid XEN_PFN_PHYS because phys_addr_t >>> * can be 32bit when dma_addr_t is 64bit leading to a loss in >>> @@ -241,7 +239,6 @@ int __ref xen_swiotlb_init(int verbose, bool early) >>> m_ret = XEN_SWIOTLB_EFIXUP; >>> goto error; >>> } >>> - start_dma_addr = xen_virt_to_bus(xen_io_tlb_start); >>> if (early) { >>> if (swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, >>> verbose)) >>> @@ -389,7 +386,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device >>> *dev, struct page *page, >>> */ >>> trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force); >>> - map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, >>> + map = swiotlb_tbl_map_single(dev, virt_to_phys(xen_io_tlb_start), >>> phys, >> >> xen_virt_to_bus() is implemented as xen_phys_to_bus(virt_to_phys()). Can you >> explain how the two are equivalent? > > They are not equivalent. Looking at what swiotlb_tbl_map_single expects, > and also the implementation of swiotlb_init_with_tbl, I think > virt_to_phys is actually the one we want. > > swiotlb_tbl_map_single compares the argument with __pa(tlb) which is > __pa(xen_io_tlb_start) which is virt_to_phys(xen_io_tlb_start). I can't find such check in master. What is your baseline? Could you point to the exact line of code? Cheers,
On Fri, 22 May 2020, Julien Grall wrote: > On 22/05/2020 04:55, Stefano Stabellini wrote: > > On Thu, 21 May 2020, Julien Grall wrote: > > > Hi, > > > > > > On 21/05/2020 00:45, Stefano Stabellini wrote: > > > > From: Stefano Stabellini <stefano.stabellini@xilinx.com> > > > > > > > > It is not strictly needed. Call virt_to_phys on xen_io_tlb_start > > > > instead. It will be useful not to have a start_dma_addr around with the > > > > next patches. > > > > > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com> > > > > --- > > > > drivers/xen/swiotlb-xen.c | 5 +---- > > > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > > > > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > > > > index a42129cba36e..b5e0492b07b9 100644 > > > > --- a/drivers/xen/swiotlb-xen.c > > > > +++ b/drivers/xen/swiotlb-xen.c > > > > @@ -52,8 +52,6 @@ static unsigned long xen_io_tlb_nslabs; > > > > * Quick lookup value of the bus address of the IOTLB. > > > > */ > > > > -static u64 start_dma_addr; > > > > - > > > > /* > > > > * Both of these functions should avoid XEN_PFN_PHYS because > > > > phys_addr_t > > > > * can be 32bit when dma_addr_t is 64bit leading to a loss in > > > > @@ -241,7 +239,6 @@ int __ref xen_swiotlb_init(int verbose, bool early) > > > > m_ret = XEN_SWIOTLB_EFIXUP; > > > > goto error; > > > > } > > > > - start_dma_addr = xen_virt_to_bus(xen_io_tlb_start); > > > > if (early) { > > > > if (swiotlb_init_with_tbl(xen_io_tlb_start, > > > > xen_io_tlb_nslabs, > > > > verbose)) > > > > @@ -389,7 +386,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device > > > > *dev, struct page *page, > > > > */ > > > > trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force); > > > > - map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, > > > > + map = swiotlb_tbl_map_single(dev, virt_to_phys(xen_io_tlb_start), > > > > phys, > > > > > > xen_virt_to_bus() is implemented as xen_phys_to_bus(virt_to_phys()). Can > > > you > > > explain how the two are equivalent? > > > > They are not equivalent. Looking at what swiotlb_tbl_map_single expects, > > and also the implementation of swiotlb_init_with_tbl, I think > > virt_to_phys is actually the one we want. > > > > swiotlb_tbl_map_single compares the argument with __pa(tlb) which is > > __pa(xen_io_tlb_start) which is virt_to_phys(xen_io_tlb_start). > > I can't find such check in master. What is your baseline? Could you point to > the exact line of code? My base is b85051e755b0e9d6dd8f17ef1da083851b83287d, which is master from a couple of days back. xen_swiotlb_init calls swiotlb_init_with_tbl which takes a virt address as a parameter (xen_io_tlb_start), it gets converted to phys and stored in io_tlb_start as a physical address. Later, xen_swiotlb_map_page calls swiotlb_tbl_map_single passing a dma addr as parameter (tbl_dma_addr). tbl_dma_addr is used to calculate the right slot in the swiotlb buffer to use. (Strangely tbl_dma_addr is a dma_addr_t and it is not converted to phys_addr_t before doing operations... I think tbl_dma_addr should be a phys addr.) The comparison with io_tlb_start is done here: do { while (iommu_is_span_boundary(index, nslots, offset_slots, max_slots)) { index += stride; if (index >= io_tlb_nslabs) index = 0; if (index == wrap) goto not_found; } index is io_tlb_start and offset_slots is derived by tbl_dma_addr.
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index a42129cba36e..b5e0492b07b9 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -52,8 +52,6 @@ static unsigned long xen_io_tlb_nslabs; * Quick lookup value of the bus address of the IOTLB. */ -static u64 start_dma_addr; - /* * Both of these functions should avoid XEN_PFN_PHYS because phys_addr_t * can be 32bit when dma_addr_t is 64bit leading to a loss in @@ -241,7 +239,6 @@ int __ref xen_swiotlb_init(int verbose, bool early) m_ret = XEN_SWIOTLB_EFIXUP; goto error; } - start_dma_addr = xen_virt_to_bus(xen_io_tlb_start); if (early) { if (swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose)) @@ -389,7 +386,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page, */ trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force); - map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, + map = swiotlb_tbl_map_single(dev, virt_to_phys(xen_io_tlb_start), phys, size, size, dir, attrs); if (map == (phys_addr_t)DMA_MAPPING_ERROR) return DMA_MAPPING_ERROR;