Re: [Qemu-devel] [PATCH v2] hw/virtio/virtio-mmio: Convert DPRINTF to traces

[Yuval Shaia <yuval.shaia@oracle.com>]

On Wed, May 01, 2019 at 08:42:35PM +0800, LI, BO XUAN wrote:
>    On Wed, May 1, 2019 at 4:58 PM Yuval Shaia <[1]yuval.shaia@oracle.com>
>    wrote:
> 
>      On Wed, May 01, 2019 at 04:10:39PM +0800, Boxuan Li wrote:
>      > Signed-off-by: Boxuan Li <[2]liboxuan@connect.hku.hk>
>      > ---
>      > v2: Instead of using conditional debugs, convert DPRINTF to traces
>      > ---
>      >  hw/virtio/trace-events  | 13 +++++++++++++
>      >  hw/virtio/virtio-mmio.c | 35 ++++++++++++-----------------------
>      >  2 files changed, 25 insertions(+), 23 deletions(-)
>      >
>      > diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
>      > index 60c649c4bc..37c781b487 100644
>      > --- a/hw/virtio/trace-events
>      > +++ b/hw/virtio/trace-events
>      > @@ -46,3 +46,16 @@ virtio_balloon_handle_output(const char *name,
>      uint64_t gpa) "section name: %s g
>      >  virtio_balloon_get_config(uint32_t num_pages, uint32_t actual)
>      "num_pages: %d actual: %d"
>      >  virtio_balloon_set_config(uint32_t actual, uint32_t oldactual)
>      "actual: %d oldactual: %d"
>      >  virtio_balloon_to_target(uint64_t target, uint32_t num_pages)
>      "balloon target: 0x%"PRIx64" num_pages: %d"
>      > +
>      > +# virtio-mmio.c
>      > +virtio_mmio_read(int offset) "virtio_mmio_read offset 0x%x"
>      > +virtio_mmio_wrong_size_read(void) "wrong size access to
>      register!"
>      > +virtio_mmio_read_interrupt(void) "read of write-only register"
>      > +virtio_mmio_bad_read_offset(void) "bad register offset"
>      > +virtio_mmio_write_offset(int offset, uint64_t value)
>      "virtio_mmio_write offset 0x%x value 0x%" PRIx64
>      > +virtio_mmio_wrong_size_write(void) "wrong size access to
>      register!"
>      > +virtio_mmio_guest_page(uint64_t size, int shift) "guest page size
>      0x%" PRIx64 " shift %d"
>      > +virtio_mmio_queue_write(int value, int max_size) "mmio_queue
>      write %d max %d"
>      > +virtio_mmio_write_interrupt(void) "write to readonly register"
>      > +virtio_mmio_bad_write_offset(void) "bad register offset"
>      > +virtio_mmio_setting_irq(int level) "virtio_mmio setting IRQ %d"
>      > diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
>      > index 5807aa87fe..4251df399d 100644
>      > --- a/hw/virtio/virtio-mmio.c
>      > +++ b/hw/virtio/virtio-mmio.c
>      > @@ -27,16 +27,7 @@
>      >  #include "sysemu/kvm.h"
>      >  #include "hw/virtio/virtio-bus.h"
>      >  #include "qemu/error-report.h"
>      > -
>      > -/* #define DEBUG_VIRTIO_MMIO */
>      > -
>      > -#ifdef DEBUG_VIRTIO_MMIO
>      > -
>      > -#define DPRINTF(fmt, ...) \
>      > -do { printf("virtio_mmio: " fmt , ## __VA_ARGS__); } while (0)
>      > -#else
>      > -#define DPRINTF(fmt, ...) do {} while (0)
>      > -#endif
>      > +#include "trace.h"
>      >
>      >  /* QOM macros */
>      >  /* virtio-mmio-bus */
>      > @@ -107,7 +98,7 @@ static uint64_t virtio_mmio_read(void *opaque,
>      hwaddr offset, unsigned size)
>      >      VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
>      >      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>      >
>      > -    DPRINTF("virtio_mmio_read offset 0x%x\n", (int)offset);
>      > +    trace_virtio_mmio_read((int)offset);
>      >
>      >      if (!vdev) {
>      >          /* If no backend is present, we treat most registers as
>      > @@ -144,7 +135,7 @@ static uint64_t virtio_mmio_read(void *opaque,
>      hwaddr offset, unsigned size)
>      >          }
>      >      }
>      >      if (size != 4) {
>      > -        DPRINTF("wrong size access to register!\n");
>      > +        trace_virtio_mmio_wrong_size_read();
>      Have you considered using qemu_error_report to report such errors?
> 
>    Thanks for the suggestion. I am a newcomer here so my question might be
>    a bit dumb: I thought they are warnings instead of errors since return
>    values are 0. Do you suggest using error_report function and changing
>    return values from 0 to -1?
>    Best regards,
>    Boxuan Li

I think that when driver store invalid data in device register it is an
error but the best is to check what other devices do.

> 
>      >          return 0;
>      >      }
>      >      switch (offset) {
>      > @@ -182,10 +173,10 @@ static uint64_t virtio_mmio_read(void
>      *opaque, hwaddr offset, unsigned size)
>      >      case VIRTIO_MMIO_QUEUE_ALIGN:
>      >      case VIRTIO_MMIO_QUEUE_NOTIFY:
>      >      case VIRTIO_MMIO_INTERRUPT_ACK:
>      > -        DPRINTF("read of write-only register\n");
>      > +        trace_virtio_mmio_read_interrupt();
>      >          return 0;
>      >      default:
>      > -        DPRINTF("bad register offset\n");
>      > +        trace_virtio_mmio_bad_read_offset();
>      Ditto to all other errors.
>      >          return 0;
>      >      }
>      >      return 0;
>      > @@ -197,8 +188,7 @@ static void virtio_mmio_write(void *opaque,
>      hwaddr offset, uint64_t value,
>      >      VirtIOMMIOProxy *proxy = (VirtIOMMIOProxy *)opaque;
>      >      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>      >
>      > -    DPRINTF("virtio_mmio_write offset 0x%x value 0x%" PRIx64
>      "\n",
>      > -            (int)offset, value);
>      > +    trace_virtio_mmio_write_offset((int)offset, value);
>      >
>      >      if (!vdev) {
>      >          /* If no backend is present, we just make all registers
>      > @@ -226,7 +216,7 @@ static void virtio_mmio_write(void *opaque,
>      hwaddr offset, uint64_t value,
>      >          return;
>      >      }
>      >      if (size != 4) {
>      > -        DPRINTF("wrong size access to register!\n");
>      > +        trace_virtio_mmio_wrong_size_write();
>      >          return;
>      >      }
>      >      switch (offset) {
>      > @@ -246,8 +236,7 @@ static void virtio_mmio_write(void *opaque,
>      hwaddr offset, uint64_t value,
>      >          if (proxy->guest_page_shift > 31) {
>      >              proxy->guest_page_shift = 0;
>      >          }
>      > -        DPRINTF("guest page size %" PRIx64 " shift %d\n", value,
>      > -                proxy->guest_page_shift);
>      > +        trace_virtio_mmio_guest_page(value,
>      proxy->guest_page_shift);
>      >          break;
>      >      case VIRTIO_MMIO_QUEUE_SEL:
>      >          if (value < VIRTIO_QUEUE_MAX) {
>      > @@ -255,7 +244,7 @@ static void virtio_mmio_write(void *opaque,
>      hwaddr offset, uint64_t value,
>      >          }
>      >          break;
>      >      case VIRTIO_MMIO_QUEUE_NUM:
>      > -        DPRINTF("mmio_queue write %d max %d\n", (int)value,
>      VIRTQUEUE_MAX_SIZE);
>      > +        trace_virtio_mmio_queue_write((int)value,
>      VIRTQUEUE_MAX_SIZE);
>      >          virtio_queue_set_num(vdev, vdev->queue_sel, value);
>      >          /* Note: only call this function for legacy devices */
>      >          virtio_queue_update_rings(vdev, vdev->queue_sel);
>      > @@ -303,11 +292,11 @@ static void virtio_mmio_write(void *opaque,
>      hwaddr offset, uint64_t value,
>      >      case VIRTIO_MMIO_DEVICE_FEATURES:
>      >      case VIRTIO_MMIO_QUEUE_NUM_MAX:
>      >      case VIRTIO_MMIO_INTERRUPT_STATUS:
>      > -        DPRINTF("write to readonly register\n");
>      > +        trace_virtio_mmio_write_interrupt();
>      >          break;
>      >
>      >      default:
>      > -        DPRINTF("bad register offset\n");
>      > +        trace_virtio_mmio_bad_write_offset();
>      >      }
>      >  }
>      >
>      > @@ -327,7 +316,7 @@ static void virtio_mmio_update_irq(DeviceState
>      *opaque, uint16_t vector)
>      >          return;
>      >      }
>      >      level = (atomic_read(&vdev->isr) != 0);
>      > -    DPRINTF("virtio_mmio setting IRQ %d\n", level);
>      > +    trace_virtio_mmio_setting_irq(level);
>      >      qemu_set_irq(proxy->irq, level);
>      >  }
>      I went through all code changes and found no mistakes but suggesting
>      to
>      turn errors to errors and not just threat them as traces.
>      If you already considered it then fine.
>      >
>      > --
>      > 2.13.2
>      >
>      >
> 
> References
> 
>    1. mailto:yuval.shaia@oracle.com
>    2. mailto:liboxuan@connect.hku.hk