Re: [Xen-devel] [PATCH 4/5] xen/swiotlb: Use theswiotlb_late_init_with_tbl to init Xen-SWIOTLB late when PV PCI is used.
From: Konrad Rzeszutek Wilk
Date: Thu Aug 23 2012 - 15:41:09 EST
On Fri, Aug 17, 2012 at 06:25:56PM +0100, Stefano Stabellini wrote:
> 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?
Yes.
>
>
> > 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.
Sure thing. Here is a stab at it.