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[Xen-devel] [RFC] Suppress all use of ISA DMA on Xen



The kernel's ISA DMA API is just not fitting virtualization requirements.

While I didn't get a response on a query regarding the change to pnpacpi,
I am going to submit both this and the floppy.c change to mainline Linux.

This was tested on 2.6.22.1, and only made apply to 2.6.18 without
further testing.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: head-2007-08-07/arch/i386/kernel/setup-xen.c
===================================================================
--- head-2007-08-07.orig/arch/i386/kernel/setup-xen.c   2007-08-08 
08:33:24.000000000 +0200
+++ head-2007-08-07/arch/i386/kernel/setup-xen.c        2007-08-07 
10:40:43.000000000 +0200
@@ -1826,6 +1826,11 @@ void __init setup_arch(char **cmdline_p)
                     virt_to_mfn(pfn_to_mfn_frame_list_list);
        }
 
+       /* Mark all ISA DMA channels in-use - using them wouldn't work. */
+       for (i = 0; i < MAX_DMA_CHANNELS; ++i)
+               if (i != 4 && request_dma(i, "xen") != 0)
+                       BUG();
+
        /*
         * NOTE: at this point the bootmem allocator is fully available.
         */
Index: head-2007-08-07/arch/x86_64/kernel/setup-xen.c
===================================================================
--- head-2007-08-07.orig/arch/x86_64/kernel/setup-xen.c 2007-08-08 
08:33:24.000000000 +0200
+++ head-2007-08-07/arch/x86_64/kernel/setup-xen.c      2007-08-07 
10:40:43.000000000 +0200
@@ -863,6 +863,10 @@ void __init setup_arch(char **cmdline_p)
                                virt_to_mfn(pfn_to_mfn_frame_list_list);
                }
 
+               /* Mark all ISA DMA channels in-use - using them wouldn't work. 
*/
+               for (i = 0; i < MAX_DMA_CHANNELS; ++i)
+                       if (i != 4 && request_dma(i, "xen") != 0)
+                               BUG();
        }
 
        if (!is_initial_xendomain()) {
Index: head-2007-08-07/drivers/block/floppy.c
===================================================================
--- head-2007-08-07.orig/drivers/block/floppy.c 2007-07-09 01:32:17.000000000 
+0200
+++ head-2007-08-07/drivers/block/floppy.c      2007-08-07 10:40:43.000000000 
+0200
@@ -4397,11 +4397,15 @@ static int floppy_grab_irq_and_dma(void)
        if (fd_request_dma()) {
                DPRINT("Unable to grab DMA%d for the floppy driver\n",
                       FLOPPY_DMA);
-               fd_free_irq();
-               spin_lock_irqsave(&floppy_usage_lock, flags);
-               usage_count--;
-               spin_unlock_irqrestore(&floppy_usage_lock, flags);
-               return -1;
+               if (can_use_virtual_dma & 2)
+                       use_virtual_dma = can_use_virtual_dma = 1;
+               if (!(can_use_virtual_dma & 1)) {
+                       fd_free_irq();
+                       spin_lock_irqsave(&floppy_usage_lock, flags);
+                       usage_count--;
+                       spin_unlock_irqrestore(&floppy_usage_lock, flags);
+                       return -1;
+               }
        }
 
        for (fdc = 0; fdc < N_FDC; fdc++) {
Index: head-2007-08-07/drivers/pnp/manager.c
===================================================================
--- head-2007-08-07.orig/drivers/pnp/manager.c  2007-04-26 05:08:32.000000000 
+0200
+++ head-2007-08-07/drivers/pnp/manager.c       2007-08-07 10:40:43.000000000 
+0200
@@ -168,7 +168,7 @@ static int pnp_assign_irq(struct pnp_dev
        return 0;
 }
 
-static int pnp_assign_dma(struct pnp_dev *dev, struct pnp_dma *rule, int idx)
+static void pnp_assign_dma(struct pnp_dev *dev, struct pnp_dma *rule, int idx)
 {
        resource_size_t *start, *end;
        unsigned long *flags;
@@ -179,18 +179,14 @@ static int pnp_assign_dma(struct pnp_dev
                1, 3, 5, 6, 7, 0, 2, 4
        };
 
-       if (!dev || !rule)
-               return -EINVAL;
-
        if (idx >= PNP_MAX_DMA) {
                pnp_err("More than 2 dmas is incompatible with pnp 
specifications.");
-               /* pretend we were successful so at least the manager won't try 
again */
-               return 1;
+               return;
        }
 
        /* check if this resource has been manually set, if so skip */
        if (!(dev->res.dma_resource[idx].flags & IORESOURCE_AUTO))
-               return 1;
+               return;
 
        start = &dev->res.dma_resource[idx].start;
        end = &dev->res.dma_resource[idx].end;
@@ -200,19 +196,17 @@ static int pnp_assign_dma(struct pnp_dev
        *flags |= rule->flags | IORESOURCE_DMA;
        *flags &=  ~IORESOURCE_UNSET;
 
-       if (!rule->map) {
-               *flags |= IORESOURCE_DISABLED;
-               return 1; /* skip disabled resource requests */
-       }
-
        for (i = 0; i < 8; i++) {
                if(rule->map & (1<<xtab[i])) {
                        *start = *end = xtab[i];
                        if(pnp_check_dma(dev, idx))
-                               return 1;
+                               return;
                }
        }
-       return 0;
+#ifdef MAX_DMA_CHANNELS
+       *start = *end = MAX_DMA_CHANNELS;
+#endif
+       *flags |= IORESOURCE_UNSET | IORESOURCE_DISABLED;
 }
 
 /**
@@ -331,8 +325,7 @@ static int pnp_assign_resources(struct p
                        irq = irq->next;
                }
                while (dma) {
-                       if (!pnp_assign_dma(dev, dma, ndma))
-                               goto fail;
+                       pnp_assign_dma(dev, dma, ndma);
                        ndma++;
                        dma = dma->next;
                }
@@ -367,8 +360,7 @@ static int pnp_assign_resources(struct p
                        irq = irq->next;
                }
                while (dma) {
-                       if (!pnp_assign_dma(dev, dma, ndma))
-                               goto fail;
+                       pnp_assign_dma(dev, dma, ndma);
                        ndma++;
                        dma = dma->next;
                }
Index: head-2007-08-07/include/asm-i386/mach-xen/asm/floppy.h
===================================================================
--- head-2007-08-07.orig/include/asm-i386/mach-xen/asm/floppy.h 2007-08-08 
08:33:24.000000000 +0200
+++ /dev/null   1970-01-01 00:00:00.000000000 +0000
@@ -1,147 +0,0 @@
-/*
- * Architecture specific parts of the Floppy driver
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 1995
- *
- * Modifications for Xen are Copyright (c) 2004, Keir Fraser.
- */
-#ifndef __ASM_XEN_I386_FLOPPY_H
-#define __ASM_XEN_I386_FLOPPY_H
-
-#include <linux/vmalloc.h>
-
-/* XEN: Hit DMA paths on the head. This trick from asm-m68k/floppy.h. */
-#include <asm/dma.h>
-#undef MAX_DMA_ADDRESS
-#define MAX_DMA_ADDRESS 0
-#define CROSS_64KB(a,s) (0)
-
-#define fd_inb(port)                   inb_p(port)
-#define fd_outb(value,port)            outb_p(value,port)
-
-#define fd_request_dma()        (0)
-#define fd_free_dma()           ((void)0)
-#define fd_enable_irq()         enable_irq(FLOPPY_IRQ)
-#define fd_disable_irq()        disable_irq(FLOPPY_IRQ)
-#define fd_free_irq()          free_irq(FLOPPY_IRQ, NULL)
-#define fd_get_dma_residue()    (virtual_dma_count + virtual_dma_residue)
-#define fd_dma_setup(addr, size, mode, io) vdma_dma_setup(addr, size, mode, io)
-/*
- * Do not use vmalloc/vfree: floppy_release_irq_and_dma() gets called from
- * softirq context via motor_off_callback. A generic bug we happen to trigger.
- */
-#define fd_dma_mem_alloc(size) __get_free_pages(GFP_KERNEL, get_order(size))
-#define fd_dma_mem_free(addr, size) free_pages(addr, get_order(size))
-
-static int virtual_dma_count;
-static int virtual_dma_residue;
-static char *virtual_dma_addr;
-static int virtual_dma_mode;
-static int doing_pdma;
-
-static irqreturn_t floppy_hardint(int irq, void *dev_id, struct pt_regs * regs)
-{
-       register unsigned char st;
-       register int lcount;
-       register char *lptr;
-
-       if (!doing_pdma)
-               return floppy_interrupt(irq, dev_id, regs);
-
-       st = 1;
-       for(lcount=virtual_dma_count, lptr=virtual_dma_addr; 
-           lcount; lcount--, lptr++) {
-               st=inb(virtual_dma_port+4) & 0xa0 ;
-               if(st != 0xa0) 
-                       break;
-               if(virtual_dma_mode)
-                       outb_p(*lptr, virtual_dma_port+5);
-               else
-                       *lptr = inb_p(virtual_dma_port+5);
-       }
-       virtual_dma_count = lcount;
-       virtual_dma_addr = lptr;
-       st = inb(virtual_dma_port+4);
-
-       if(st == 0x20)
-               return IRQ_HANDLED;
-       if(!(st & 0x20)) {
-               virtual_dma_residue += virtual_dma_count;
-               virtual_dma_count=0;
-               doing_pdma = 0;
-               floppy_interrupt(irq, dev_id, regs);
-               return IRQ_HANDLED;
-       }
-       return IRQ_HANDLED;
-}
-
-static void fd_disable_dma(void)
-{
-       doing_pdma = 0;
-       virtual_dma_residue += virtual_dma_count;
-       virtual_dma_count=0;
-}
-
-static int fd_request_irq(void)
-{
-       return request_irq(FLOPPY_IRQ, floppy_hardint,
-                          IRQF_DISABLED, "floppy", NULL);
-}
-
-static int vdma_dma_setup(char *addr, unsigned long size, int mode, int io)
-{
-       doing_pdma = 1;
-       virtual_dma_port = io;
-       virtual_dma_mode = (mode  == DMA_MODE_WRITE);
-       virtual_dma_addr = addr;
-       virtual_dma_count = size;
-       virtual_dma_residue = 0;
-       return 0;
-}
-
-/* XEN: This trick to force 'virtual DMA' is from include/asm-m68k/floppy.h. */
-#define FDC1 xen_floppy_init()
-static int FDC2 = -1;
-
-static int xen_floppy_init(void)
-{
-       use_virtual_dma = 1;
-       can_use_virtual_dma = 1;
-       return 0x3f0;
-}
-
-/*
- * Floppy types are stored in the rtc's CMOS RAM and so rtc_lock
- * is needed to prevent corrupted CMOS RAM in case "insmod floppy"
- * coincides with another rtc CMOS user.               Paul G.
- */
-#define FLOPPY0_TYPE   ({                              \
-       unsigned long flags;                            \
-       unsigned char val;                              \
-       spin_lock_irqsave(&rtc_lock, flags);            \
-       val = (CMOS_READ(0x10) >> 4) & 15;              \
-       spin_unlock_irqrestore(&rtc_lock, flags);       \
-       val;                                            \
-})
-
-#define FLOPPY1_TYPE   ({                              \
-       unsigned long flags;                            \
-       unsigned char val;                              \
-       spin_lock_irqsave(&rtc_lock, flags);            \
-       val = CMOS_READ(0x10) & 15;                     \
-       spin_unlock_irqrestore(&rtc_lock, flags);       \
-       val;                                            \
-})
-
-#define N_FDC 2
-#define N_DRIVE 8
-
-#define FLOPPY_MOTOR_MASK 0xf0
-
-#define EXTRA_FLOPPY_PARAMS
-
-#endif /* __ASM_XEN_I386_FLOPPY_H */
Index: head-2007-08-07/include/asm-i386/mach-xen/asm/io.h
===================================================================
--- head-2007-08-07.orig/include/asm-i386/mach-xen/asm/io.h     2007-08-08 
08:33:56.000000000 +0200
+++ head-2007-08-07/include/asm-i386/mach-xen/asm/io.h  2007-08-08 
08:34:11.000000000 +0200
@@ -152,7 +152,7 @@ extern void bt_iounmap(void *addr, unsig
 /*
  * ISA I/O bus memory addresses are 1:1 with the physical address.
  */
-#define isa_virt_to_bus(_x) isa_virt_to_bus_is_UNSUPPORTED->x
+#define isa_virt_to_bus(_x) ({ BUG(); virt_to_bus(_x); })
 #define isa_page_to_bus(_x) isa_page_to_bus_is_UNSUPPORTED->x
 #define isa_bus_to_virt(_x) (void *)(__fix_to_virt(FIX_ISAMAP_BEGIN) + (_x))
 
Index: head-2007-08-07/include/asm-x86_64/mach-xen/asm/floppy.h
===================================================================
--- head-2007-08-07.orig/include/asm-x86_64/mach-xen/asm/floppy.h       
2007-08-08 08:33:24.000000000 +0200
+++ /dev/null   1970-01-01 00:00:00.000000000 +0000
@@ -1,206 +0,0 @@
-/*
- * Architecture specific parts of the Floppy driver
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 1995
- *
- * Modifications for Xen are Copyright (c) 2004, Keir Fraser.
- */
-#ifndef __ASM_XEN_X86_64_FLOPPY_H
-#define __ASM_XEN_X86_64_FLOPPY_H
-
-#include <linux/vmalloc.h>
-
-/*
- * The DMA channel used by the floppy controller cannot access data at
- * addresses >= 16MB
- *
- * Went back to the 1MB limit, as some people had problems with the floppy
- * driver otherwise. It doesn't matter much for performance anyway, as most
- * floppy accesses go through the track buffer.
- */
-#define _CROSS_64KB(a,s,vdma) \
-(!(vdma) && ((unsigned long)(a)/K_64 != ((unsigned long)(a) + (s) - 1) / K_64))
-
-/* XEN: Hit DMA paths on the head. This trick from asm-m68k/floppy.h. */
-#include <asm/dma.h>
-#undef MAX_DMA_ADDRESS
-#define MAX_DMA_ADDRESS 0
-#define CROSS_64KB(a,s) (0)
-
-#define fd_inb(port)                   inb_p(port)
-#define fd_outb(value,port)            outb_p(value,port)
-
-#define fd_request_dma()        (0)
-#define fd_free_dma()           ((void)0)
-#define fd_enable_irq()         enable_irq(FLOPPY_IRQ)
-#define fd_disable_irq()        disable_irq(FLOPPY_IRQ)
-#define fd_free_irq()          free_irq(FLOPPY_IRQ, NULL)
-#define fd_get_dma_residue()    vdma_get_dma_residue(FLOPPY_DMA)
-/*
- * Do not use vmalloc/vfree: floppy_release_irq_and_dma() gets called from
- * softirq context via motor_off_callback. A generic bug we happen to trigger.
- */
-#define fd_dma_mem_alloc(size) __get_free_pages(GFP_KERNEL|__GFP_NORETRY, 
get_order(size))
-#define fd_dma_mem_free(addr, size) free_pages(addr, get_order(size))
-#define fd_dma_setup(addr, size, mode, io) vdma_dma_setup(addr, size, mode, io)
-
-static int virtual_dma_count;
-static int virtual_dma_residue;
-static char *virtual_dma_addr;
-static int virtual_dma_mode;
-static int doing_pdma;
-
-static irqreturn_t floppy_hardint(int irq, void *dev_id, struct pt_regs * regs)
-{
-       register unsigned char st;
-
-#undef TRACE_FLPY_INT
-
-#ifdef TRACE_FLPY_INT
-       static int calls=0;
-       static int bytes=0;
-       static int dma_wait=0;
-#endif
-       if (!doing_pdma)
-               return floppy_interrupt(irq, dev_id, regs);
-
-#ifdef TRACE_FLPY_INT
-       if(!calls)
-               bytes = virtual_dma_count;
-#endif
-
-       {
-               register int lcount;
-               register char *lptr;
-
-               st = 1;
-               for(lcount=virtual_dma_count, lptr=virtual_dma_addr; 
-                   lcount; lcount--, lptr++) {
-                       st=inb(virtual_dma_port+4) & 0xa0 ;
-                       if(st != 0xa0) 
-                               break;
-                       if(virtual_dma_mode)
-                               outb_p(*lptr, virtual_dma_port+5);
-                       else
-                               *lptr = inb_p(virtual_dma_port+5);
-               }
-               virtual_dma_count = lcount;
-               virtual_dma_addr = lptr;
-               st = inb(virtual_dma_port+4);
-       }
-
-#ifdef TRACE_FLPY_INT
-       calls++;
-#endif
-       if(st == 0x20)
-               return IRQ_HANDLED;
-       if(!(st & 0x20)) {
-               virtual_dma_residue += virtual_dma_count;
-               virtual_dma_count=0;
-#ifdef TRACE_FLPY_INT
-               printk("count=%x, residue=%x calls=%d bytes=%d dma_wait=%d\n", 
-                      virtual_dma_count, virtual_dma_residue, calls, bytes,
-                      dma_wait);
-               calls = 0;
-               dma_wait=0;
-#endif
-               doing_pdma = 0;
-               floppy_interrupt(irq, dev_id, regs);
-               return IRQ_HANDLED;
-       }
-#ifdef TRACE_FLPY_INT
-       if(!virtual_dma_count)
-               dma_wait++;
-#endif
-       return IRQ_HANDLED;
-}
-
-static void fd_disable_dma(void)
-{
-       doing_pdma = 0;
-       virtual_dma_residue += virtual_dma_count;
-       virtual_dma_count=0;
-}
-
-static int vdma_get_dma_residue(unsigned int dummy)
-{
-       return virtual_dma_count + virtual_dma_residue;
-}
-
-
-static int fd_request_irq(void)
-{
-       return request_irq(FLOPPY_IRQ, floppy_hardint,
-                          IRQF_DISABLED, "floppy", NULL);
-}
-
-#if 0
-static unsigned long vdma_mem_alloc(unsigned long size)
-{
-       return (unsigned long) vmalloc(size);
-
-}
-
-static void vdma_mem_free(unsigned long addr, unsigned long size)
-{
-       vfree((void *)addr);
-}
-#endif
-
-static int vdma_dma_setup(char *addr, unsigned long size, int mode, int io)
-{
-       doing_pdma = 1;
-       virtual_dma_port = io;
-       virtual_dma_mode = (mode  == DMA_MODE_WRITE);
-       virtual_dma_addr = addr;
-       virtual_dma_count = size;
-       virtual_dma_residue = 0;
-       return 0;
-}
-
-/* XEN: This trick to force 'virtual DMA' is from include/asm-m68k/floppy.h. */
-#define FDC1 xen_floppy_init()
-static int FDC2 = -1;
-
-static int xen_floppy_init(void)
-{
-       use_virtual_dma = 1;
-       can_use_virtual_dma = 1;
-       return 0x3f0;
-}
-
-/*
- * Floppy types are stored in the rtc's CMOS RAM and so rtc_lock
- * is needed to prevent corrupted CMOS RAM in case "insmod floppy"
- * coincides with another rtc CMOS user.               Paul G.
- */
-#define FLOPPY0_TYPE   ({                              \
-       unsigned long flags;                            \
-       unsigned char val;                              \
-       spin_lock_irqsave(&rtc_lock, flags);            \
-       val = (CMOS_READ(0x10) >> 4) & 15;              \
-       spin_unlock_irqrestore(&rtc_lock, flags);       \
-       val;                                            \
-})
-
-#define FLOPPY1_TYPE   ({                              \
-       unsigned long flags;                            \
-       unsigned char val;                              \
-       spin_lock_irqsave(&rtc_lock, flags);            \
-       val = CMOS_READ(0x10) & 15;                     \
-       spin_unlock_irqrestore(&rtc_lock, flags);       \
-       val;                                            \
-})
-
-#define N_FDC 2
-#define N_DRIVE 8
-
-#define FLOPPY_MOTOR_MASK 0xf0
-
-#define EXTRA_FLOPPY_PARAMS
-
-#endif /* __ASM_XEN_X86_64_FLOPPY_H */
Index: head-2007-08-07/include/asm-x86_64/mach-xen/asm/io.h
===================================================================
--- head-2007-08-07.orig/include/asm-x86_64/mach-xen/asm/io.h   2007-08-07 
10:20:55.000000000 +0200
+++ head-2007-08-07/include/asm-x86_64/mach-xen/asm/io.h        2007-08-07 
10:40:43.000000000 +0200
@@ -164,7 +164,7 @@ extern void iounmap(volatile void __iome
  * ISA I/O bus memory addresses are 1:1 with the physical address.
  */
 
-#define isa_virt_to_bus(_x) isa_virt_to_bus_is_UNSUPPORTED->x
+#define isa_virt_to_bus(_x) ({ BUG(); virt_to_bus(_x); })
 #define isa_page_to_bus(_x) isa_page_to_bus_is_UNSUPPORTED->x
 #define isa_bus_to_virt(_x) (void *)(__fix_to_virt(FIX_ISAMAP_BEGIN) + (_x))
 



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