Re: [Xen-devel] [PATCH 4/5] xen/swiotlb: Use the swiotlb_late_init_with_tbl to init Xen-SWIOTLB late when PV PCI is used.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 16 Aug 2012, Konrad Rzeszutek Wilk wrote:
> With this patch we provide the functionality to initialize the
> Xen-SWIOTLB late in the bootup cycle - specifically for
> Xen PCI-frontend. We still will work if the user had
> supplied 'iommu=soft' on the Linux command line.
> 
> CC: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
> [v1: Fix smatch warnings]
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>  arch/x86/include/asm/xen/swiotlb-xen.h |    2 +
>  arch/x86/xen/pci-swiotlb-xen.c         |   17 +++++++++-
>  drivers/xen/swiotlb-xen.c              |   54 ++++++++++++++++++++++++++-----
>  include/xen/swiotlb-xen.h              |    1 +
>  4 files changed, 64 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/include/asm/xen/swiotlb-xen.h 
> b/arch/x86/include/asm/xen/swiotlb-xen.h
> index 1be1ab7..ee52fca 100644
> --- a/arch/x86/include/asm/xen/swiotlb-xen.h
> +++ b/arch/x86/include/asm/xen/swiotlb-xen.h
> @@ -5,10 +5,12 @@
>  extern int xen_swiotlb;
>  extern int __init pci_xen_swiotlb_detect(void);
>  extern void __init pci_xen_swiotlb_init(void);
> +extern int pci_xen_swiotlb_init_late(void);
>  #else
>  #define xen_swiotlb (0)
>  static inline int __init pci_xen_swiotlb_detect(void) { return 0; }
>  static inline void __init pci_xen_swiotlb_init(void) { }
> +static inline int pci_xen_swiotlb_init_late(void) { return -ENXIO; }
>  #endif
>  
>  #endif /* _ASM_X86_SWIOTLB_XEN_H */
> diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
> index 1c17227..031d8bc 100644
> --- a/arch/x86/xen/pci-swiotlb-xen.c
> +++ b/arch/x86/xen/pci-swiotlb-xen.c
> @@ -12,7 +12,7 @@
>  #include <asm/iommu.h>
>  #include <asm/dma.h>
>  #endif
> -
> +#include <linux/export.h>
>  int xen_swiotlb __read_mostly;
>  
>  static struct dma_map_ops xen_swiotlb_dma_ops = {
> @@ -76,6 +76,21 @@ void __init pci_xen_swiotlb_init(void)
>               pci_request_acs();
>       }
>  }
> +
> +int pci_xen_swiotlb_init_late(void)
> +{
> +     int rc = xen_swiotlb_late_init(1);
> +     if (rc)
> +             return rc;
> +
> +     dma_ops = &xen_swiotlb_dma_ops;
> +     /* Make sure ACS will be enabled */
> +     pci_request_acs();
> +
> +     return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);

shouldn't we be checking whether the xen_swiotlb has already been
initialized?


>  IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
>                 0,
>                 pci_xen_swiotlb_init,
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 1afb4fb..1942a3e 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -145,13 +145,14 @@ xen_swiotlb_fixup(void *buf, size_t size, unsigned long 
> nslabs)
>       return 0;
>  }
>  
> -void __init xen_swiotlb_init(int verbose)
> +static int __ref __xen_swiotlb_init(int verbose, bool early)
>  {
>       unsigned long bytes;
>       int rc = -ENOMEM;
>       unsigned long nr_tbl;
>       char *m = NULL;
>       unsigned int repeat = 3;
> +     unsigned long order;
>
>       nr_tbl = swiotlb_nr_tbl();
>       if (nr_tbl)
> @@ -161,12 +162,31 @@ void __init xen_swiotlb_init(int verbose)
>               xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
>       }
>  retry:
> +     order = get_order(xen_io_tlb_nslabs << IO_TLB_SHIFT);
>       bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
>  
>       /*
>        * Get IO TLB memory from any location.
>        */
> -     xen_io_tlb_start = alloc_bootmem_pages(PAGE_ALIGN(bytes));
> +     if (early)
> +             xen_io_tlb_start = alloc_bootmem_pages(PAGE_ALIGN(bytes));
> +     else {
> +#define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
> +#define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)


> +             while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
> +                     xen_io_tlb_start = (void 
> *)__get_free_pages(__GFP_NOWARN, order);
> +                     if (xen_io_tlb_start)
> +                             break;
> +                     order--;
> +             }
> +             if (order != get_order(bytes)) {
> +                     pr_warn("Warning: only able to allocate %ld MB "
> +                             "for software IO TLB\n", (PAGE_SIZE << order) 
> >> 20);
> +                     xen_io_tlb_nslabs = SLABS_PER_PAGE << order;
> +                     bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
> +             }
> +     }
>       if (!xen_io_tlb_start) {
>               m = "Cannot allocate Xen-SWIOTLB buffer!\n";
>               goto error;
> @@ -179,17 +199,22 @@ retry:
>                              bytes,
>                              xen_io_tlb_nslabs);
>       if (rc) {
> -             free_bootmem(__pa(xen_io_tlb_start), PAGE_ALIGN(bytes));
> +             if (early)
> +                     free_bootmem(__pa(xen_io_tlb_start), PAGE_ALIGN(bytes));
>               m = "Failed to get contiguous memory for DMA from Xen!\n"\
>                   "You either: don't have the permissions, do not have"\
>                   " enough free memory under 4GB, or the hypervisor memory"\
> -                 "is too fragmented!";
> +                 " is too fragmented!";
>               goto error;
>       }
>       start_dma_addr = xen_virt_to_bus(xen_io_tlb_start);
> -     swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose);
>  
> -     return;
> +     rc = 0;
> +     if (early)
> +             swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, 
> verbose);
> +     else
> +             rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, 
> xen_io_tlb_nslabs);
> +     return rc;
>  error:
>       if (repeat--) {
>               xen_io_tlb_nslabs = max(1024UL, /* Min is 2MB */
> @@ -198,10 +223,21 @@ error:
>                     (xen_io_tlb_nslabs << IO_TLB_SHIFT) >> 20);
>               goto retry;
>       }
> -     xen_raw_printk("%s (rc:%d)", m, rc);
> -     panic("%s (rc:%d)", m, rc);
> +     pr_err("%s (rc:%d)", m, rc);
> +     if (early)
> +             panic("%s (rc:%d)", m, rc);
> +     else
> +             free_pages((unsigned long)xen_io_tlb_start, order);
> +     return rc;
> +}

All these "if" make the code a harder to read. Would it be possible at
least to unify the error paths and just check on after_bootmem whether
we need to call free_pages or free_bootmem?
In fact using after_bootmem you might get away without an early
parameter.


> +void __init xen_swiotlb_init(int verbose)
> +{
> +     __xen_swiotlb_init(verbose, true /* early */);
> +}
> +int xen_swiotlb_late_init(int verbose)
> +{
> +     return __xen_swiotlb_init(verbose, false /* late */);
>  }
>  void *
>  xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>                          dma_addr_t *dma_handle, gfp_t flags,
> diff --git a/include/xen/swiotlb-xen.h b/include/xen/swiotlb-xen.h
> index 4f4d449..d38d984 100644
> --- a/include/xen/swiotlb-xen.h
> +++ b/include/xen/swiotlb-xen.h
> @@ -4,6 +4,7 @@
>  #include <linux/swiotlb.h>
>  
>  extern void xen_swiotlb_init(int verbose);
> +extern int  xen_swiotlb_late_init(int verbose);
>  
>  extern void
>  *xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
> -- 
> 1.7.7.6
> 
> 
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> http://lists.xen.org/xen-devel
> 

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