Re: [Qemu-devel] [PATCH v2 3/3] hw: correctly implement soft reset

[Paolo Bonzini <pbonzini@redhat.com>]

Il 06/03/2013 10:06, li guang ha scritto:
> 在 2013-03-06三的 09:36 +0100，Paolo Bonzini写道：
>> > Il 06/03/2013 03:02, li guang ha scritto:
>>> > > 在 2013-03-05二的 20:00 +0100，Paolo Bonzini写道：
>>>> > >> Do not do a hard reset for port 92h, keyboard controller, or cf9h soft reset.
>>>> > >> These only reset the CPU.
>>>> > >>
>>>> > >> Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
>>>> > >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>>> > >> ---
>>>> > >>  hw/lpc_ich9.c | 7 ++++++-
>>>> > >>  hw/pc.c       | 3 ++-
>>>> > >>  hw/pckbd.c    | 5 +++--
>>>> > >>  hw/piix_pci.c | 8 ++++++--
>>>> > >>  4 files changed, 17 insertions(+), 6 deletions(-)
>>>> > >>
>>>> > >> diff --git a/hw/lpc_ich9.c b/hw/lpc_ich9.c
>>>> > >> index e473758..5540f61 100644
>>>> > >> --- a/hw/lpc_ich9.c
>>>> > >> +++ b/hw/lpc_ich9.c
>>>> > >> @@ -45,6 +45,7 @@
>>>> > >>  #include "pci/pci_bus.h"
>>>> > >>  #include "exec/address-spaces.h"
>>>> > >>  #include "sysemu/sysemu.h"
>>>> > >> +#include "sysemu/cpus.h"
>>>> > >>  
>>>> > >>  static int ich9_lpc_sci_irq(ICH9LPCState *lpc);
>>>> > >>  
>>>> > >> @@ -506,7 +507,11 @@ static void ich9_rst_cnt_write(void *opaque, hwaddr addr, uint64_t val,
>>>> > >>      ICH9LPCState *lpc = opaque;
>>>> > >>  
>>>> > >>      if (val & 4) {
>>>> > >> -        qemu_system_reset_request();
>>>> > >> +        if (val & 0xA) {
>>>> > >> +            qemu_system_reset_request();
>>>> > >> +        } else {
>>>> > >> +            cpu_reset_all_async();
>>>> > >> +        }
>>>> > >>          return;
>>> > > 
>>> > > in fact, soft reset is cpu reset, hard reset is platform reset,
>>> > > it is too harsh to require both bit 3 & 1 to do a system reset,
>>> > > they are independent, either of them can trigger that.
>> > 
>> > This is "full reset if (val & 0xA) != 0".  You interpreted it as (val &
>> > 0xA) = 0xA, I think.
>
> No, IMHO, full reset should be done only by bit 4.

Ah, you mean by bit 1, as in bit 3 only being consulted if bit 1 is 1.
Hence, writing 0xC should do an INIT# cycle, not a full reset.  It would
matter if you want a watchdog to do a full power cycle (asserting
SLP_S3/4/5#), but you want to use cf9h to do a CPU reset.  That could be
the case.

> that is bit 1 & 2 are combined to determined reset cpu/system.
> and system reset does not always be the same with full reset(
> mostly be different in hardware signal of power cycle),

The ICH9 datasheet says exactly how the two differ.  For a full reset,
ICH9 will drive SLP_S3/4/5# low for 3-5 seconds.  We do not emulate this
in QEMU.

> it's up to the board hardware designer.
> 
>> > 
>>>> > >>      }
>>>> > >>      lpc->rst_cnt = val & 0xA; /* keep FULL_RST (bit 3) and SYS_RST (bit 1) */
>>>> > >> diff --git a/hw/pc.c b/hw/pc.c
>>>> > >> index 3e1cf2e..54f5b72 100644
>>>> > >> --- a/hw/pc.c
>>>> > >> +++ b/hw/pc.c
>>>> > >> @@ -45,6 +45,7 @@
>>>> > >>  #include "kvm_i386.h"
>>>> > >>  #include "xen.h"
>>>> > >>  #include "sysemu/blockdev.h"
>>>> > >> +#include "sysemu/cpus.h"
>>>> > >>  #include "hw/block-common.h"
>>>> > >>  #include "ui/qemu-spice.h"
>>>> > >>  #include "exec/memory.h"
>>>> > >> @@ -443,7 +444,7 @@ static void port92_write(void *opaque, hwaddr addr, uint64_t val,
>>>> > >>      s->outport = val;
>>>> > >>      qemu_set_irq(*s->a20_out, (val >> 1) & 1);
>>>> > >>      if ((val & 1) && !(oldval & 1)) {
>>>> > >> -        qemu_system_reset_request();
>>>> > >> +        cpu_reset_all_async();
>>>> > >>      }
>>>> > >>  }
>>>> > >>  
>>>> > >> diff --git a/hw/pckbd.c b/hw/pckbd.c
>>>> > >> index 3bad09b..fd66788 100644
>>>> > >> --- a/hw/pckbd.c
>>>> > >> +++ b/hw/pckbd.c
>>>> > >> @@ -26,6 +26,7 @@
>>>> > >>  #include "pc.h"
>>>> > >>  #include "ps2.h"
>>>> > >>  #include "sysemu/sysemu.h"
>>>> > >> +#include "sysemu/cpus.h"
>>>> > >>  
>>>> > >>  /* debug PC keyboard */
>>>> > >>  //#define DEBUG_KBD
>>>> > >> @@ -220,7 +221,7 @@ static void outport_write(KBDState *s, uint32_t val)
>>>> > >>          qemu_set_irq(*s->a20_out, (val >> 1) & 1);
>>>> > >>      }
>>>> > >>      if (!(val & 1)) {
>>>> > >> -        qemu_system_reset_request();
>>>> > >> +        cpu_reset_all_async();
>>>> > >>      }
>>>> > >>  }
>>>> > >>  
>>>> > >> @@ -299,7 +300,7 @@ static void kbd_write_command(void *opaque, hwaddr addr,
>>>> > >>          s->outport &= ~KBD_OUT_A20;
>>>> > >>          break;
>>>> > >>      case KBD_CCMD_RESET:
>>>> > >> -        qemu_system_reset_request();
>>>> > >> +        cpu_reset_all_async();
>>> > > 
>>> > > Oh, no, system reset is correct.
>> > 
>> > No, the keyboard controller is connected to the CPU reset signal.
> Not always, AFAIK,
> traditionally, this should do system reset,
> though system reset may be triggered by INIT# which 
> I guess is you said "CPU reset signal".

Some websites say it is a system reset, but I don't think it's ever been
correct.  But on PIIX and ICH9 the keyboard controller reset is
connected to INIT#, which is definitely not a system reset.

Paolo