Re: [Qemu-devel] [PULL 00/14] Migration pull request

[Peter Lieven]

Am 20.11.2015 um 14:53 schrieb Kevin Wolf:
> Am 20.11.2015 um 14:44 hat Peter Lieven geschrieben:
>> Am 20.11.2015 um 12:33 schrieb Peter Maydell:
>>> On 20 November 2015 at 09:38, Peter Lieven <address@hidden> wrote:
>>>> I wonder if there is a glitch in the PIO implementation of test-ide.c. As 
>>>> far as I understand the specs
>>>> it is not allowed to read data while the BSY flag is set. With the 
>>>> following change to the test-ide script
>>>> the test does not race:
>>>>
>>>> diff --git a/tests/ide-test.c b/tests/ide-test.c
>>>> index d1014bb..ab0489e 100644
>>>> --- a/tests/ide-test.c
>>>> +++ b/tests/ide-test.c
>>>> @@ -728,6 +728,7 @@ static void cdrom_pio_impl(int nblocks)
>>>>      for (i = 0; i < DIV_ROUND_UP(rxsize, limit); i++) {
>>>>          size_t offset = i * (limit / 2);
>>>>          size_t rem = (rxsize / 2) - offset;
>>>> +        ide_wait_clear(BSY);
>>>>          for (j = 0; j < MIN((limit / 2), rem); j++) {
>>>>              rx[offset + j] = le16_to_cpu(inw(IDE_BASE + reg_data));
>>>>          }
>>>>
>>>> Note: in the old sync version of the ATAPI PIO implementation this could 
>>>> not happen.
>>> This certainly fixes the stalls for me, though I don't know enough
>>> IDE to say whether it is the correct fix.
>> Thanks for testing.
>>
>> I hope that John or Kevin can verify this fix?
> The fix looks correct to me.
>
> While you're improving the test, you could also add an assertion that
> DRQ is set after BSY has been cleared.

I would actually move the check (which is already there) into the loop:

diff --git a/tests/ide-test.c b/tests/ide-test.c
index d1014bb..d7ee376 100644
--- a/tests/ide-test.c
+++ b/tests/ide-test.c
@@ -712,11 +712,6 @@ static void cdrom_pio_impl(int nblocks)
     /* HPD3: INTRQ_Wait */
     ide_wait_intr(IDE_PRIMARY_IRQ);
 
-    /* HPD2: Check_Status_B */
-    data = ide_wait_clear(BSY);
-    assert_bit_set(data, DRQ | DRDY);
-    assert_bit_clear(data, ERR | DF | BSY);
-
     /* Read data back: occurs in bursts of 'BYTE_COUNT_LIMIT' bytes.
      * If BYTE_COUNT_LIMIT is odd, we transfer BYTE_COUNT_LIMIT - 1 bytes.
      * We allow an odd limit only when the remaining transfer size is
@@ -728,6 +723,10 @@ static void cdrom_pio_impl(int nblocks)
     for (i = 0; i < DIV_ROUND_UP(rxsize, limit); i++) {
         size_t offset = i * (limit / 2);
         size_t rem = (rxsize / 2) - offset;
+        /* HPD2: Check_Status_B */
+        data = ide_wait_clear(BSY);
+        assert_bit_set(data, DRQ | DRDY);
+        assert_bit_clear(data, ERR | DF | BSY);
         for (j = 0; j < MIN((limit / 2), rem); j++) {
             rx[offset + j] = le16_to_cpu(inw(IDE_BASE + reg_data));
         }

Are you okay with that? @John, you also?

Peter