Re: [Qemu-devel] [PATCH v3 02/26] blockdev: Introduce IF_AHCI

[Jason Baron <jbaron@redhat.com>]

On Wed, Oct 24, 2012 at 05:50:25PM +0200, Markus Armbruster wrote:
> Jason Baron <jbaron@redhat.com> writes:
> 
> > On Mon, Oct 22, 2012 at 01:40:21PM +0200, Kevin Wolf wrote:
> >> >> From: Jason Baron <jbaron@redhat.com>
> >> >>
> >> >> Introduce IF_AHCI so that q35 can differentiate between ide and ahci disks.
> >> >> This allows q35 to specify its default disk type. It also allows q35 to
> >> >> differentiate between ahci and ide disks, such that -drive if=ide does not
> >> >> result in the creating of an ahci disk. This is important, since
> >> >> we don't want
> >> >> to have the meaning of if=ide changing once q35 is introduced. Thus, its
> >> >> important for this to be applied before we introduce q35.
> 
> This isn't the real argument for IF_AHCI.  The real argument is that the
> (bus, unit) namespace for if=ide makes no sense for AHCI.
> 
> A board can have any number of IDE controllers.  Each IDE controller
> provides one or two buses, and each bus takes up to two units.
> Together, we get a a board-specific number of buses, where each bus
> takes up to two units.
> 
> A board can have any number of AHCI controllers.  Each AHCI controller
> provides a device-specific number of ports.  Together, we get a
> board-specific number of buses, where each bus can takes a bus-specific
> number of units.
> 
> Plain q35 doesn't really need to differentiate between IDE and AHCI; it
> has only AHCI.  What it needs is a "one bus with six units" namespace.
> 
> We could fix this by relaxing if=ide's rigid "two units per bus" for new
> machine types.
> 
> You fix it by introducing if=ahci.  Probably simpler.  But what's the
> plan for the next generation of controller?  Yet another interface type?

Next generation might require a new interface type. But taking you're
suggestions, if=ahci is now machine dependent, so it shouldn't be so bad
(see incremental patch at end).

> 
> Note that SCSI suffers from similar rigidity: seven units per bus.
> That's fine for SCSI-1, but not for some of the other variants.
> 
> "Differentiate" comes into play when a board sports both AHCI and IDE
> controllers.  Which q35 doesn't, does it?

Yes, there is no ide controller by default. That said i've used the
piix-ide controller to install windows xp, for example, on q35.

> 
> Then, the new if=ahci lets users select the kind of controller more
> easily than bus numbers would.
> 
> Drawback: existing command lines upgrade from pc to plain q35 gracefully
> only if they don't specify if=ide explicitly.  Upgrading to some q35
> variant with IDE controller on board is even worse: it works, but
> performance sucks.  Some regard this as a feature.
> 

well if=ide could give a warning on q35, suggesting using if=ahci, if
we're not going to create an ide controller for if=ide (which I wasn't
intending).

> >> >> This patch also adds:
> >> >>
> >> >> pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table)
> >> >>
> >> >> Which provides a convient way of attaching ahci drives to an
> >> >> ahci controller.
> >> >>
> >> >> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> >> >> Signed-off-by: Jason Baron <jbaron@redhat.com>
> >> >> ---
> >> > 
> >> > Kevin, could you review/ack this patch pls?
> >> > 
> >> >>  blockdev.c    |   13 ++++++++++++-
> >> >>  blockdev.h    |    2 ++
> >> >>  hw/ide.h      |    6 ++++++
> >> >>  hw/ide/ahci.c |   18 ++++++++++++++++++
> >> >>  hw/ide/core.c |   23 ++++++++++++++++++-----
> >> >>  5 files changed, 56 insertions(+), 6 deletions(-)
> >> >>
> >> >> diff --git a/blockdev.c b/blockdev.c
> >> >> index c9a49c8..b684348 100644
> >> >> --- a/blockdev.c
> >> >> +++ b/blockdev.c
> >> >> @@ -33,6 +33,7 @@ static const char *const if_name[IF_COUNT] = {
> >> >>      [IF_SD] = "sd",
> >> >>      [IF_VIRTIO] = "virtio",
> >> >>      [IF_XEN] = "xen",
> >> >> +    [IF_AHCI] = "ahci",
> >> >>  };
> >> >>  
> >> >>  static const int if_max_devs[IF_COUNT] = {
> >> >> @@ -52,8 +53,17 @@ static const int if_max_devs[IF_COUNT] = {
>            /*
>             * Do not change these numbers!  They govern how drive option
>             * index maps to unit and bus.  That mapping is ABI.
>             *
>             * All controllers used to imlement if=T drives need to support
>             * if_max_devs[T] units, for any T with if_max_devs[T] != 0.
>             * Otherwise, some index values map to "impossible" bus, unit
>             * values.
>             *
>             * For instance, if you change [IF_SCSI] to 255, -drive
>             * if=scsi,index=12 no longer means bus=1,unit=5, but
>             * bus=0,unit=12.  With an lsi53c895a controller (7 units max),
>             * the drive can't be set up.  Regression.
> >> >>       */
> >> >>      [IF_IDE] = 2,
> >> >>      [IF_SCSI] = 7,
> >> >> +    [IF_AHCI] = 6,
> >> >>  };
> >> 
> >> What are the implications of this if we decided to add another AHCI
> >> controller which had a different number of ports? I suspect that a
> >> controller with less than 6 ports breaks when you add more drives than a
> >> single controller can handle, and one with more than 6 ports doesn't use
> >> up all of its ports before it adds another controller.
> >> 
> >> Markus?
> >> 
> >
> > My plan was to make this field, machine dependent if/when we wanted a different
> > size. I don't think it breaks anything to make this change at a later
> > point. But please correct me, if I am wrong.
> 
> I'm afraid you are.  See the comment immediately above, and commit
> 27d6bf40.
> 
> As far as I can see, the least bad solution is leaving
> if_max_devs[IF_AHCI] zero.  Makes index=N an alias for unit=N,bus=0, and
> leaves rejecting invalid (bus,unit) to the board.
> 

Ok. I've done that. And it makes if=ahci machine dependent.

> >> >> +int get_if_max_devs(BlockInterfaceType if_type)
> >> >> +{
> >> >> +    assert(if_type < IF_COUNT);
> >> >> +    assert(if_type >= IF_DEFAULT);
> >> >> +
> >> >> +    return if_max_devs[if_type];
> >> >> +}
> >> 
> >> if_max_devs has a specific obvious meaning within blockdev.c, but
> >> outside it's not as obvious. So this function could use a rename.
> >
> > ok.
> 
> No, get rid of it.  if_max_devs[]'s purpose is mapping between index and
> (bus, unit), no more.  See below.
> 

done.

> >> >>  /*
> >> >>   * We automatically delete the drive when a device using it gets
> >> >>   * unplugged.  Questionable feature, but we can't just drop it.
> >> >> @@ -518,7 +528,7 @@ DriveInfo *drive_init(QemuOpts *opts, int mach_if)
> >> >>      } else {
> >> >>          /* no id supplied -> create one */
> >> >>          dinfo->id = g_malloc0(32);
> >> >> -        if (type == IF_IDE || type == IF_SCSI)
> >> >> +        if (type == IF_IDE || type == IF_SCSI || type == IF_AHCI)
> >> >>              mediastr = (media == MEDIA_CDROM) ? "-cd" : "-hd";
> >> >>          if (max_devs)
> >> >>              snprintf(dinfo->id, 32, "%s%i%s%i",
> >> >> @@ -550,6 +560,7 @@ DriveInfo *drive_init(QemuOpts *opts, int mach_if)
> >> >>  
> >> >>      switch(type) {
> >> >>      case IF_IDE:
> >> >> +    case IF_AHCI:
> >> >>      case IF_SCSI:
> >> >>      case IF_XEN:
> >> >>      case IF_NONE:
> >> >> diff --git a/blockdev.h b/blockdev.h
> >> >> index 8b126ad..bbd1017 100644
> >> >> --- a/blockdev.h
> >> >> +++ b/blockdev.h
> >> >> @@ -21,6 +21,7 @@ typedef enum {
> >> >>      IF_DEFAULT = -1,            /* for use with drive_add() only */
> >> >>      IF_NONE,
> >> >>      IF_IDE, IF_SCSI, IF_FLOPPY, IF_PFLASH, IF_MTD, IF_SD, IF_VIRTIO, IF_XEN,
> >> >> +    IF_AHCI,
> >> >>      IF_COUNT
> >> >>  } BlockInterfaceType;
> >> >>  
> >> >> @@ -56,6 +57,7 @@ static inline int get_mach_if(int mach_if)
> >> >>      return mach_if;
> >> >>  }
> >> >>  
> >> >> +int get_if_max_devs(BlockInterfaceType if_type);
> >> >>  DriveInfo *drive_get(BlockInterfaceType type, int bus, int unit);
> >> >>  DriveInfo *drive_get_by_index(BlockInterfaceType type, int index);
> >> >>  int drive_get_max_bus(BlockInterfaceType type);
> >> >> diff --git a/hw/ide.h b/hw/ide.h
> >> >> index 2db4079..0b7e000 100644
> >> >> --- a/hw/ide.h
> >> >> +++ b/hw/ide.h
> >> >> @@ -4,6 +4,7 @@
> >> >>  #include "isa.h"
> >> >>  #include "pci.h"
> >> >>  #include "memory.h"
> >> >> +#include "blockdev.h"
> >> >>  
> >> >>  #define MAX_IDE_DEVS	2
> >> >>  
> >> >> @@ -34,6 +35,11 @@ int ide_get_geometry(BusState *bus, int unit,
> >> >>  int ide_get_bios_chs_trans(BusState *bus, int unit);
> >> >>  
> >> >>  /* ide/core.c */
> >> >> +void ata_drive_get(DriveInfo **hd, int max_bus, BlockInterfaceType type);
> >> >>  void ide_drive_get(DriveInfo **hd, int max_bus);
> >> >> +void ahci_drive_get(DriveInfo **hd, int max_bus);
> >> >> +
> >> >> +/* ide/ahci.c */
> >> >> +void pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table);
> 
> Shouldn't this go next to pci_ide_create_devs()'s declaration?
> Currently in hw/ide/pci.h.
> 

done.

> >> >>  
> >> >>  #endif /* HW_IDE_H */
> >> >> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> >> >> index 68671bc..824b86f 100644
> >> >> --- a/hw/ide/ahci.c
> >> >> +++ b/hw/ide/ahci.c
> >> >> @@ -26,6 +26,7 @@
> >> >>  #include <hw/pc.h>
> >> >>  #include <hw/pci.h>
> >> >>  #include <hw/sysbus.h>
> >> >> +#include <blockdev.h>
> >> >>  
> >> >>  #include "monitor.h"
> >> >>  #include "dma.h"
> >> >> @@ -1260,3 +1261,20 @@ static void sysbus_ahci_register_types(void)
> >> >>  }
> >> >>  
> >> >>  type_init(sysbus_ahci_register_types)
> >> >> +
> >> >> +void pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table)
> >> >> +{
> >> >> +    struct AHCIPCIState *dev = DO_UPCAST(struct AHCIPCIState, card, pci_dev);
> >> >> +    int i;
> >> >> +    DriveInfo *drive;
> >> >> +
> >> >> +    for (i = 0; i < dev->ahci.ports; i++) {
> >> >> +        if (hd_table[i] == NULL) {
> >> >> +            continue;
> >> >> +        }
> >> >> +        drive = hd_table[i];
> >> >> +        assert(drive->type == IF_AHCI);
> >> >> +        ide_create_drive(&dev->ahci.dev[i].port, 0,
> >> >> +                         hd_table[i]);
> >> >> +    }
> >> >> +}
> 
> Shouldn't this go next to pci_ide_create_devs()'s definition?  Currently
> in hw/ide/pci.c.
> 
> Consider adding a parameter for the number of elements in hd_table[],
> for robustness.  As is, the caller has to ensure hd_table[] has at least
> dev->ahci.ports elements, which is not obvious from the function
> signature.
> 
> >> >> diff --git a/hw/ide/core.c b/hw/ide/core.c
> >> >> index d683a8c..044da3c 100644
> >> >> --- a/hw/ide/core.c
> >> >> +++ b/hw/ide/core.c
> >> >> @@ -2341,16 +2341,29 @@ const VMStateDescription vmstate_ide_bus = {
> >> >>      }
> >> >>  };
> >> >>  
> >> >> -void ide_drive_get(DriveInfo **hd, int max_bus)
> >> >> +void ata_drive_get(DriveInfo **hd, int max_bus, BlockInterfaceType type)
> >> 
> >> Could be static?
> >> 
> >
> > Yes.
> >
> >> >>  {
> >> >>      int i;
> >> >> +    int max_devs;
> >> >> +
> >> >> +    assert((type == IF_IDE) || type == IF_AHCI);
> >> 
> >> Interesting use of brackets.
> >
> > oops.
> >
> >> 
> >> >>  
> >> >> -    if (drive_get_max_bus(IF_IDE) >= max_bus) {
> >> >> +    if (drive_get_max_bus(type) >= max_bus) {
> >> >>          fprintf(stderr, "qemu: too many IDE bus: %d\n", max_bus);
> >> 
> >> "Too many %s buses", type == IF_IDE ? "IDE" : "AHCI"
> >
> > ok.
> >
> >> 
> >> >>          exit(1);
> >> >>      }
> >> >> -
> >> >> -    for(i = 0; i < max_bus * MAX_IDE_DEVS; i++) {
> >> >> -        hd[i] = drive_get(IF_IDE, i / MAX_IDE_DEVS, i % MAX_IDE_DEVS);
> >> >> +    max_devs = get_if_max_devs(type);
> >> >> +    for (i = 0; i < max_bus * max_devs; i++) {
> >> >> +        hd[i] = drive_get(type, i / max_devs, i % max_devs);
> >> >>      }
> >> >>  }
> >> >> +
> >> >> +void ide_drive_get(DriveInfo **hd, int max_bus)
> >> >> +{
> >> >> +    ata_drive_get(hd, max_bus, IF_IDE);
> >> >> +}
> >> >> +
> >> >> +void ahci_drive_get(DriveInfo **hd, int max_bus)
> >> >> +{
> >> >> +    ata_drive_get(hd, max_bus, IF_AHCI);
> >> >> +}
> 
> For IDE, we always have two devices per bus.  The boards number of buses
> varies in theory, and is always two in practice.  Thus we have "#define
> MAX_IDE_DEVS 2" in ide.h, and "#define MAX_IDE_BUS 2" in all the
> <board>.c.  The latter is passed to ide_drive_get() as parameter.
> Getting the well-known MAX_IDE_DEVS from get_if_max_devs() buys us
> nothing.
> 
> For AHCI, I figure we have a device-specific number of ports per device,
> and a board-specific number of devices (typically one).  If there are
> multiple devices, they don't necessarily sport the same number of ports.
> Thus, a nested loop does not work.
> 
> Suggest
> 
>     void ahci_drive_get(DriveInfo **hd, int bus, int max_ports)
> 
> which the board can call once for each device, with the device's true
> number of ports as argument.  Look ma, no get_if_max_devs()!

Agreed.

So here is an incremental patch. If its too hard to read I'll send a
full diff - I'd like to include something like this in my next q35
series. thoughts?

Thanks,

-Jason


diff --git a/blockdev.c b/blockdev.c
index b684348..e17016e 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -53,17 +53,9 @@ static const int if_max_devs[IF_COUNT] = {
      */
     [IF_IDE] = 2,
     [IF_SCSI] = 7,
-    [IF_AHCI] = 6,
+    [IF_AHCI] = 0,
 };
 
-int get_if_max_devs(BlockInterfaceType if_type)
-{
-    assert(if_type < IF_COUNT);
-    assert(if_type >= IF_DEFAULT);
-
-    return if_max_devs[if_type];
-}
-
 /*
  * We automatically delete the drive when a device using it gets
  * unplugged.  Questionable feature, but we can't just drop it.
@@ -168,6 +160,20 @@ int drive_get_max_bus(BlockInterfaceType type)
     return max_bus;
 }
 
+int drive_get_max_unit(BlockInterfaceType type)
+{
+    int max_unit;
+    DriveInfo *dinfo;
+
+    max_unit = -1;
+    QTAILQ_FOREACH(dinfo, &drives, next) {
+        if(dinfo->type == type &&
+           dinfo->unit > max_unit)
+            max_unit = dinfo->unit;
+    }
+    return max_unit;
+}
+
 /* Get a block device.  This should only be used for single-drive devices
    (e.g. SD/Floppy/MTD).  Multi-disk devices (scsi/ide) should use the
    appropriate bus.  */
diff --git a/blockdev.h b/blockdev.h
index bbd1017..250f9d8 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -61,6 +61,7 @@ int get_if_max_devs(BlockInterfaceType if_type);
 DriveInfo *drive_get(BlockInterfaceType type, int bus, int unit);
 DriveInfo *drive_get_by_index(BlockInterfaceType type, int index);
 int drive_get_max_bus(BlockInterfaceType type);
+int drive_get_max_unit(BlockInterfaceType type);
 DriveInfo *drive_get_next(BlockInterfaceType type);
 void drive_get_ref(DriveInfo *dinfo);
 void drive_put_ref(DriveInfo *dinfo);
diff --git a/hw/ide.h b/hw/ide.h
index 0b7e000..54e485f 100644
--- a/hw/ide.h
+++ b/hw/ide.h
@@ -35,11 +35,7 @@ int ide_get_geometry(BusState *bus, int unit,
 int ide_get_bios_chs_trans(BusState *bus, int unit);
 
 /* ide/core.c */
-void ata_drive_get(DriveInfo **hd, int max_bus, BlockInterfaceType type);
 void ide_drive_get(DriveInfo **hd, int max_bus);
-void ahci_drive_get(DriveInfo **hd, int max_bus);
-
-/* ide/ahci.c */
-void pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table);
+void ahci_drive_get(DriveInfo **hd, int max_bus, int max_ports);
 
 #endif /* HW_IDE_H */
diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index 824b86f..1e389aa 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -1261,20 +1261,3 @@ static void sysbus_ahci_register_types(void)
 }
 
 type_init(sysbus_ahci_register_types)
-
-void pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table)
-{
-    struct AHCIPCIState *dev = DO_UPCAST(struct AHCIPCIState, card, pci_dev);
-    int i;
-    DriveInfo *drive;
-
-    for (i = 0; i < dev->ahci.ports; i++) {
-        if (hd_table[i] == NULL) {
-            continue;
-        }
-        drive = hd_table[i];
-        assert(drive->type == IF_AHCI);
-        ide_create_drive(&dev->ahci.dev[i].port, 0,
-                         hd_table[i]);
-    }
-}
diff --git a/hw/ide/core.c b/hw/ide/core.c
index 044da3c..6fc2626 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -2341,18 +2341,17 @@ const VMStateDescription vmstate_ide_bus = {
     }
 };
 
-void ata_drive_get(DriveInfo **hd, int max_bus, BlockInterfaceType type)
+static void ata_drive_get(DriveInfo **hd, int max_bus, int max_devs,
+                          BlockInterfaceType type)
 {
     int i;
-    int max_devs;
 
-    assert((type == IF_IDE) || type == IF_AHCI);
+    assert((type == IF_IDE) || (type == IF_AHCI));
 
-    if (drive_get_max_bus(type) >= max_bus) {
+    if ((type == IF_IDE) && (drive_get_max_bus(type) >= max_bus)) {
         fprintf(stderr, "qemu: too many IDE bus: %d\n", max_bus);
         exit(1);
     }
-    max_devs = get_if_max_devs(type);
     for (i = 0; i < max_bus * max_devs; i++) {
         hd[i] = drive_get(type, i / max_devs, i % max_devs);
     }
@@ -2360,10 +2359,10 @@ void ata_drive_get(DriveInfo **hd, int max_bus, BlockInterfaceType type)
 
 void ide_drive_get(DriveInfo **hd, int max_bus)
 {
-    ata_drive_get(hd, max_bus, IF_IDE);
+    ata_drive_get(hd, max_bus, MAX_IDE_DEVS, IF_IDE);
 }
 
-void ahci_drive_get(DriveInfo **hd, int max_bus)
+void ahci_drive_get(DriveInfo **hd, int max_bus, int max_ports)
 {
-    ata_drive_get(hd, max_bus, IF_AHCI);
+    ata_drive_get(hd, max_bus, max_ports, IF_AHCI);
 }
diff --git a/hw/ide/pci.c b/hw/ide/pci.c
index 644533f..2df6b57 100644
--- a/hw/ide/pci.c
+++ b/hw/ide/pci.c
@@ -30,6 +30,7 @@
 #include "dma.h"
 
 #include <hw/ide/pci.h>
+#include <hw/ide/ahci.h>
 
 #define BMDMA_PAGE_SIZE 4096
 
@@ -504,6 +505,24 @@ void pci_ide_create_devs(PCIDevice *dev, DriveInfo **hd_table)
     }
 }
 
+
+void pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table, int table_size)
+{
+    struct AHCIPCIState *dev = DO_UPCAST(struct AHCIPCIState, card, pci_dev);
+    int i;
+    DriveInfo *drive;
+
+    for (i = 0; i < table_size; i++) {
+        if (hd_table[i] == NULL) {
+            continue;
+        }
+        drive = hd_table[i];
+        assert(drive->type == IF_AHCI);
+        ide_create_drive(&dev->ahci.dev[i].port, 0,
+                         hd_table[i]);
+    }
+}
+
 static const struct IDEDMAOps bmdma_ops = {
     .start_dma = bmdma_start_dma,
     .start_transfer = bmdma_start_transfer,
diff --git a/hw/ide/pci.h b/hw/ide/pci.h
index a694e54..6a0d500 100644
--- a/hw/ide/pci.h
+++ b/hw/ide/pci.h
@@ -58,6 +58,8 @@ void bmdma_init(IDEBus *bus, BMDMAState *bm, PCIIDEState *d);
 void bmdma_cmd_writeb(BMDMAState *bm, uint32_t val);
 extern MemoryRegionOps bmdma_addr_ioport_ops;
 void pci_ide_create_devs(PCIDevice *dev, DriveInfo **hd_table);
+void pci_ahci_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table, int table_size);
+
 
 extern const VMStateDescription vmstate_ide_pci;
 #endif