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Re: [Qemu-devel] [PATCH v2] s390x/pci: add common fmb


From: Yi Min Zhao
Subject: Re: [Qemu-devel] [PATCH v2] s390x/pci: add common fmb
Date: Tue, 23 Oct 2018 15:50:48 +0800
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1



在 2018/10/22 下午8:17, Thomas Huth 写道:
On 2018-10-22 10:02, Yi Min Zhao wrote:
Common function measurement block is used to report counters of
successfully issued pcilg/stg/stb and rpcit instructions. This patch
introduces a new struct ZpciFmb and schedules a timer callback to
copy fmb to the guest memory at a interval time which is set to
4s by default. While attemping to update fmb failed, an event error
would be generated. After pcilg/stg/stb and rpcit interception
handlers issue successfully, increase the related counter. The guest
could pass null address to switch off FMB and stop corresponding
timer.

Signed-off-by: Yi Min Zhao <address@hidden>
Reviewed-by: Pierre Morel <address@hidden>
---
[...]
+static int fmb_do_update(S390PCIBusDevice *pbdev, uint8_t offset, int len)
+{
+    MemTxResult ret;
+
+    ret = address_space_write(&address_space_memory,
+                              pbdev->fmb_addr + (uint64_t)offset,
+                              MEMTXATTRS_UNSPECIFIED,
+                              (uint8_t *)&pbdev->fmb + offset,
+                              len);
+    if (ret) {
+        s390_pci_generate_error_event(ERR_EVENT_FMBA, pbdev->fh, pbdev->fid,
+                                      pbdev->fmb_addr, 0);
+        fmb_timer_free(pbdev);
+    }
+
+    return ret;
+}
+
+static void fmb_update(void *opaque)
+{
+    S390PCIBusDevice *pbdev = opaque;
+    int64_t t = qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL);
+    uint8_t offset = offsetof(ZpciFmb, last_update);
+
+    /* Update U bit */
+    pbdev->fmb.last_update |= UPDATE_U_BIT;
+    if (fmb_do_update(pbdev, offset, sizeof(uint64_t))) {
+        return;
+    }
+
+    /* Update FMB counters */
+    pbdev->fmb.sample++;
+    if (fmb_do_update(pbdev, 0, sizeof(ZpciFmb))) {
+        return;
+    }
+
+    /* Clear U bit and update the time */
+    pbdev->fmb.last_update = time2tod(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
+    pbdev->fmb.last_update &= ~UPDATE_U_BIT;
+    if (fmb_do_update(pbdev, offset, sizeof(uint64_t))) {
+        return;
+    }
+
+    timer_mod(pbdev->fmb_timer, t + DEFAULT_MUI);
+}
Sorry for noticing this in v1 already, but is this code endianess-safe?
I.e. can this also work with qemu-system-s390x running with TCG on a x86
host? I think you might have to use something like this here instead:

   pbdev->fmb.sample = cpu_to_be32(be32_to_cpu(pbdev->fmb.sample) + 1);

etc.

  Thomas


Aha!!! Yes, I think you're right. Indeed, we should consider endianess.

--
Yi Min




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