Re: [Qemu-devel] [PATCH] raw-posix.c: Make physical devices usable in QEMU

[Laurent Vivier <lvivier@redhat.com>]

On 07/07/2015 19:33, Programmingkid wrote:
> Make physical devices like a USB flash drive or a CDROM drive work in
> QEMU. With
> this patch I can use a USB flash drive like a hard drive. Before this
> patch, 
> QEMU would just quit with a message like "resource busy". Now it handles
> issues
> like these for the user. This patch unmounts volumes of physical devices
> before
> using them in QEMU. When QEMU quits, the physical devices are mounted again
> for the user. The user can find out which device files to use for their
> physical
> devices by running the mount command in the terminal. This patch makes
> "qemu-system-ppc -cdrom /dev/cdrom" work again on Mac OS X.
> 
> Signed-off-by: John Arbuckle <programmingkidx@gmail.com
> <mailto:programmingkidx@gmail.com>>

Two comments:
- you should not mix several fixes in one patch (raw block device
management, partition seek, unmount/mount cdrom...)
- according to Stefan answer, I think you should not unmount the CDROM
but you should inform the user he must unmount it manually to be able to
use it.

Laurent
> ---
>  block/raw-posix.c |  155
> ++++++++++++++++++++++++++++++++++++++++++++--------
>  1 files changed, 131 insertions(+), 24 deletions(-)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index cbe6574..af0981a 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -42,9 +42,10 @@
>  #include <IOKit/storage/IOMediaBSDClient.h>
>  #include <IOKit/storage/IOMedia.h>
>  #include <IOKit/storage/IOCDMedia.h>
> -//#include <IOKit/storage/IOCDTypes.h>
>  #include <CoreFoundation/CoreFoundation.h>
> -#endif
> +#include <sys/syslimits.h>
> +#include <fcntl.h>
> +#endif /* (__APPLE__) && (__MACH__) */
> 
>  
> 
>  #ifdef __sun__
>  #define _POSIX_PTHREAD_SEMANTICS 1
> @@ -162,6 +163,25 @@ typedef struct BDRVRawState {
>      bool needs_alignment;
>  } BDRVRawState;
> 
>  
> 
> +#ifdef __APPLE__
> +
> +#define MAX_NUM_DEVICES 7
> +
> +/*
> + * Keeps track of devices that need to be mounted
> + * when QEMU exists.
> + */
> +typedef struct {
> +    int fd;
> +    char filePath[MAXPATHLEN];
> +} PhysicalDevice;
> +
> +PhysicalDevice deviceArray[MAX_NUM_DEVICES];
> +int numberOfDevices;
> +
> +#endif /* __APPLE__ */
> +
> +
>  typedef struct BDRVRawReopenState {
>      int fd;
>      int open_flags;
> @@ -1972,8 +1992,10 @@ BlockDriver bdrv_file = {
>  /* host device */
> 
>  
> 
>  #if defined(__APPLE__) && defined(__MACH__)
> -static kern_return_t FindEjectableCDMedia( io_iterator_t *mediaIterator );
> -static kern_return_t GetBSDPath( io_iterator_t mediaIterator, char
> *bsdPath, CFIndex maxPathSize );
> +static kern_return_t FindEjectableCDMedia(io_iterator_t *mediaIterator);
> +static kern_return_t GetBSDPath(io_iterator_t mediaIterator, char *bsdPath,
> +                                CFIndex maxPathSize, int flags);
> +void mountDevice(void);
> 
>  
> 
>  kern_return_t FindEjectableCDMedia( io_iterator_t *mediaIterator )
>  {
> @@ -2001,7 +2023,8 @@ kern_return_t FindEjectableCDMedia( io_iterator_t
> *mediaIterator )
>      return kernResult;
>  }
> 
>  
> 
> -kern_return_t GetBSDPath( io_iterator_t mediaIterator, char *bsdPath,
> CFIndex maxPathSize )
> +kern_return_t GetBSDPath(io_iterator_t mediaIterator, char *bsdPath,
> +                         CFIndex maxPathSize, int flags)
>  {
>      io_object_t     nextMedia;
>      kern_return_t   kernResult = KERN_FAILURE;
> @@ -2014,7 +2037,9 @@ kern_return_t GetBSDPath( io_iterator_t
> mediaIterator, char *bsdPath, CFIndex ma
>          if ( bsdPathAsCFString ) {
>              size_t devPathLength;
>              strcpy( bsdPath, _PATH_DEV );
> -            strcat( bsdPath, "r" );
> +            if (flags & BDRV_O_NOCACHE) {
> +                strcat(bsdPath, "r");
> +            }
>              devPathLength = strlen( bsdPath );
>              if ( CFStringGetCString( bsdPathAsCFString, bsdPath +
> devPathLength, maxPathSize - devPathLength, kCFStringEncodingASCII ) ) {
>                  kernResult = KERN_SUCCESS;
> @@ -2027,7 +2052,54 @@ kern_return_t GetBSDPath( io_iterator_t
> mediaIterator, char *bsdPath, CFIndex ma
>      return kernResult;
>  }
> 
>  
> 
> -#endif
> +/* Mounts unmounted devices onto host computer's desktop */
> +void mountDevice(void)
> +{
> +    char commandBuffer[MAXPATHLEN];
> +    int result, index;
> +
> +    for (index = 0; index < numberOfDevices; index++) {
> +        qemu_close(deviceArray[index].fd);
> +        sprintf(commandBuffer, "diskutil mountDisk %s",
> +                                               
> deviceArray[index].filePath);
> +        DPRINTF("Issuing command: %s\n", commandBuffer);
> +        result = system(commandBuffer);
> +        if (result != 0) {
> +            printf("Warning: problem detected while mounting %s\n",
> +                                               
> deviceArray[index].filePath);
> +        }
> +    }
> +}
> +
> +/* Sets up a real cdrom for use in QEMU */
> +static void setupCDROM(char *bsdPath)
> +{
> +    int index, numOfTestPartitions = 2, fd;
> +    char testPartition[MAXPATHLEN];
> +    bool partitionFound = false;
> +
> +    /* look for a working partition */
> +    for (index = 0; index < numOfTestPartitions; index++) {
> +        strcpy(testPartition, bsdPath);
> +        sprintf(testPartition, "%ss%d", testPartition, index);
> +        fd = qemu_open(testPartition, O_RDONLY | O_BINARY | O_LARGEFILE);
> +        if (fd > 0) {
> +            partitionFound = true;
> +            qemu_close(fd);
> +            break;
> +        }
> +    }
> +
> +    /* if a working partition on the device was found */
> +    if (partitionFound == false) {
> +        printf("Error: Failed to find a working partition on CD!\n");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    strcpy(bsdPath, testPartition);
> +}
> +
> +#endif /* defined(__APPLE__) && defined(__MACH__) */
> 
>  
> 
>  static int hdev_probe_device(const char *filename)
>  {
> @@ -2119,30 +2191,52 @@ static int hdev_open(BlockDriverState *bs, QDict
> *options, int flags,
>  #if defined(__APPLE__) && defined(__MACH__)
>      const char *filename = qdict_get_str(options, "filename");
> 
>  
> 
> -    if (strstart(filename, "/dev/cdrom", NULL)) {
> -        kern_return_t kernResult;
> -        io_iterator_t mediaIterator;
> +    /* If using a physical device */
> +    if (strstart(filename, "/dev/", NULL)) {
>          char bsdPath[ MAXPATHLEN ];
> -        int fd;
> 
>  
> 
> -        kernResult = FindEjectableCDMedia( &mediaIterator );
> -        kernResult = GetBSDPath( mediaIterator, bsdPath, sizeof(
> bsdPath ) );
> +        /* If the physical device is a cdrom */
> +        if (strcmp(filename, "/dev/cdrom") == 0) {
> +            io_iterator_t mediaIterator;
> +            FindEjectableCDMedia(&mediaIterator);
> +            GetBSDPath(mediaIterator, bsdPath, sizeof(bsdPath), flags);
> +            if (mediaIterator) {
> +                IOObjectRelease(mediaIterator);
> +            }
> +        }
> 
>  
> 
> -        if ( bsdPath[ 0 ] != '\0' ) {
> -            strcat(bsdPath,"s0");
> -            /* some CDs don't have a partition 0 */
> -            fd = qemu_open(bsdPath, O_RDONLY | O_BINARY | O_LARGEFILE);
> -            if (fd < 0) {
> -                bsdPath[strlen(bsdPath)-1] = '1';
> -            } else {
> -                qemu_close(fd);
> +        /* If the physical device is something else */
> +        else {
> +            strcpy(bsdPath, filename);
> +        }
> +
> +        /* if accessing a buffered device */
> +        if ((flags & BDRV_O_NOCACHE) == 0) {
> +            /*
> +            * Unmount the device from the desktop before
> +            * using the buffered device. A resource busy error
> +            * would happen if we don't.
> +            */
> +            char commandBuffer[MAXPATHLEN];
> +            int result;
> +            sprintf(commandBuffer, "diskutil unmountDisk %s", bsdPath);
> +            DPRINTF("Issuing command: %s\n", commandBuffer);
> +            result = system(commandBuffer);
> +            if (result != 0) {
> +                printf("Warning: problem detected while unmounting %s\n",
> +                                                                   
> bsdPath);
>              }
> +        }
> +
> +        atexit(mountDevice);
> +
> +        /* Setup a CDROM device if found */
> +        if (bsdPath[0] != '\0' && (strcmp(filename, "/dev/cdrom") == 0)) {
> +            setupCDROM(bsdPath);
> +            DPRINTF("Using %s as CDROM\n", bsdPath);
>              filename = bsdPath;
>              qdict_put(options, "filename", qstring_from_str(filename));
>          }
> -
> -        if ( mediaIterator )
> -            IOObjectRelease( mediaIterator );
>      }
>  #endif
> 
>  
> 
> @@ -2156,6 +2250,19 @@ static int hdev_open(BlockDriverState *bs, QDict
> *options, int flags,
>          return ret;
>      }
> 
>  
> 
> +#ifdef __APPLE__
> +
> +    /* Add the fd to the fd array for mounting at exit */
> +    if (strncmp(filename, "/dev/", 5) == 0) {
> +        int mountFD = ((BDRVRawState *) bs->opaque)->fd;
> +        DPRINTF("Queuing %s (fd: %d) for mounting at exit\n",
> +                                                            filename,
> mountFD);
> +        deviceArray[numberOfDevices].fd = mountFD;
> +        strcpy(deviceArray[numberOfDevices++].filePath, filename);
> +    }
> +
> +#endif /* __APPLE__ */
> +
>      /* Since this does ioctl the device must be already opened */
>      bs->sg = hdev_is_sg(bs);
> 
>  
> 
> -- 
> 1.7.5.4
>