Re: [Qemu-devel] [PATCH 14/25] spapr: push the XIVE EQ data in OS event queue

[Cédric Le Goater]

On 12/01/2017 05:10 AM, David Gibson wrote:
> On Thu, Nov 30, 2017 at 02:16:30PM +0000, Cédric Le Goater wrote:
>> On 11/30/2017 04:49 AM, David Gibson wrote:
>>> On Thu, Nov 23, 2017 at 02:29:44PM +0100, Cédric Le Goater wrote:
>>>> If a triggered event is let through, the Event Queue data defined in the
>>>> associated IVE is pushed in the in-memory event queue. The latter is a
>>>> circular buffer provided by the OS using the H_INT_SET_QUEUE_CONFIG hcall,
>>>> one per server and priority couple. It is composed of Event Queue entries
>>>> which are 4 bytes long, the first bit being a 'generation' bit and the 31
>>>> following bits the EQ Data field.
>>>>
>>>> The EQ Data field provides a way to set an invariant logical event source
>>>> number for an IRQ. It is set with the H_INT_SET_SOURCE_CONFIG hcall.
>>>>
>>>> Signed-off-by: Cédric Le Goater <address@hidden>
>>>> ---
>>>>  hw/intc/spapr_xive.c | 67 
>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 67 insertions(+)
>>>>
>>>> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
>>>> index 983317a6b3f6..df14c5a88275 100644
>>>> --- a/hw/intc/spapr_xive.c
>>>> +++ b/hw/intc/spapr_xive.c
>>>> @@ -193,9 +193,76 @@ static sPAPRXiveICP *spapr_xive_icp_get(sPAPRXive 
>>>> *xive, int server)
>>>>      return cpu ? SPAPR_XIVE_ICP(cpu->intc) : NULL;
>>>>  }
>>>>  
>>>> +static void spapr_xive_eq_push(XiveEQ *eq, uint32_t data)
>>>> +{
>>>> +    uint64_t qaddr_base = (((uint64_t)(eq->w2 & 0x0fffffff)) << 32) | 
>>>> eq->w3;
>>>> +    uint32_t qsize = GETFIELD(EQ_W0_QSIZE, eq->w0);
>>>> +    uint32_t qindex = GETFIELD(EQ_W1_PAGE_OFF, eq->w1);
>>>> +    uint32_t qgen = GETFIELD(EQ_W1_GENERATION, eq->w1);
>>>> +
>>>> +    uint64_t qaddr = qaddr_base + (qindex << 2);
>>>> +    uint32_t qdata = cpu_to_be32((qgen << 31) | (data & 0x7fffffff));
>>>> +    uint32_t qentries = 1 << (qsize + 10);
>>>> +
>>>> +    if (dma_memory_write(&address_space_memory, qaddr, &qdata, 
>>>> sizeof(qdata))) {
>>>
>>> This suggests that uint32_t data contains guest endian data, which it
>>> generally shouldn't.  Better to use stl_be_dma() (or whatever is
>>> appropriate for the endianness of the data field.
>>
>> There are no requirement on the endianness of the data field and 
>> it is just stored in the IVE in the hcall H_INT_SET_SOURCE_CONFIG. 
>> So the guest can pass whatever it likes.  
> 
> Hm, ok.  Guest endian (or at least, not definitively host-endian) data
> in a plain uint32_t makes me uncomfortable.  Could we use char data[4]
> instead, to make it clear it's a byte-ordered buffer, rather than a
> number as far as the XIVE is concerned.
> 
> Hm.. except that doesn't quite work, because the hardware must define
> which end that generation bit ends up in...

Sorry, this is is BE. My bad.

C.
 
>>>> +        qemu_log_mask(LOG_GUEST_ERROR, "%s: failed to write EQ data @0x%"
>>>> +                      HWADDR_PRIx "\n", __func__, qaddr);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    qindex = (qindex + 1) % qentries;
>>>> +    if (qindex == 0) {
>>>> +        qgen ^= 1;
>>>> +        eq->w1 = SETFIELD(EQ_W1_GENERATION, eq->w1, qgen);
>>>> +    }
>>>> +    eq->w1 = SETFIELD(EQ_W1_PAGE_OFF, eq->w1, qindex);
>>>> +}
>>>> +
>>>>  static void spapr_xive_irq(sPAPRXive *xive, int lisn)
>>>>  {
>>>> +    XiveIVE *ive;
>>>> +    XiveEQ *eq;
>>>> +    uint32_t eq_idx;
>>>> +    uint8_t priority;
>>>> +
>>>> +    ive = spapr_xive_get_ive(xive, lisn);
>>>> +    if (!ive || !(ive->w & IVE_VALID)) {
>>>> +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid LISN %d\n", lisn);
>>>
>>> As mentioned on other patches, I'm a little concerned by these
>>> guest-triggerable logs.  I guess the LOG_GUEST_ERROR mask will save
>>> us, though.
>>
>> I want to track 'invalid' interrupts but I haven't seen these show up 
>> in my tests. I agree there are a little too much and some could just 
>> be asserts.
> 
> Uh.. I don't think many can be assert()s.  assert() is only
> appropriate if it being tripped definitely indicates a bug in qemu.
> Nearly all these qemu_log()s I've seen can be tripped by the guest
> doing something bad, which absolutely should not assert() qemu.
>