From: Dongli Zhang <dongli.zhang@oracle.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: berrange@redhat.com, ehabkost@redhat.com, mst@redhat.com,
jasowang@redhat.com, joe.jin@oracle.com, qemu-devel@nongnu.org,
dgilbert@redhat.com, pbonzini@redhat.com
Subject: Re: [PATCH v3 1/3] msix/hmp: add hmp interface to dump MSI-X info
Date: Tue, 13 Jul 2021 23:17:14 -0700 [thread overview]
Message-ID: <ae859cde-5d56-01f8-4ef8-bffce9303ff1@oracle.com> (raw)
In-Reply-To: <8735shmorf.fsf@dusky.pond.sub.org>
Hi Markus,
On 7/13/21 10:46 PM, Markus Armbruster wrote:
> Dongli Zhang <dongli.zhang@oracle.com> writes:
>
>> This patch is to add the HMP interface to dump MSI-X table and PBA, in
>> order to help diagnose the loss of IRQ issue in VM (e.g., if an MSI-X
>> vector is erroneously masked permanently). Here is the example with
>> vhost-scsi:
>>
>> (qemu) info msix /machine/peripheral/vscsi0
>> Msg L.Addr Msg U.Addr Msg Data Vect Ctrl
>> 0xfee00000 0x00000000 0x00004041 0x00000000
>> 0xfee00000 0x00000000 0x00004051 0x00000000
>> 0xfee00000 0x00000000 0x00004061 0x00000000
>> 0xfee00000 0x00000000 0x00004071 0x00000000
>> 0xfee01000 0x00000000 0x000040b1 0x00000000
>> 0xfee02000 0x00000000 0x000040c1 0x00000000
>> 0xfee03000 0x00000000 0x000040d1 0x00000000
>>
>> MSI-X PBA
>> 0 0 0 0 0 0 0
>>
>> Since the number of MSI-X entries is not determined and might be very
>> large, it is sometimes inappropriate to dump via QMP.
>
> Why? What makes HMP different?
Here are two reasons.
1. The size of MSI-X table is nondeterministic and might be very large, e.g.,
the PCI_MSIX_FLAGS_QSIZE is 0x07FF. The "info tlb" (which is a table and similar
to MSI-X) and "info lapic" also only support hmp.
2. The [PATCH 3/3] of this patchset support device specific data, the
definitional of which varies depending on each device type (so far only
virtio-pci supports the interface).
Thank you very much!
Dongli Zhang
>
>> Therefore, this patch dumps MSI-X information only via HMP, which is
>> similar to the implementation of hmp_info_mem().
>>
>> Cc: Jason Wang <jasowang@redhat.com>
>> Cc: Joe Jin <joe.jin@oracle.com>
>> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
>> Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>> Acked-by: Jason Wang <jasowang@redhat.com>
>
next prev parent reply other threads:[~2021-07-14 6:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 0:47 [PATCH v3 0/3] To add HMP interface to dump PCI MSI-X table/PBA Dongli Zhang
2021-07-14 0:47 ` [PATCH v3 1/3] msix/hmp: add hmp interface to dump MSI-X info Dongli Zhang
2021-07-14 5:46 ` Markus Armbruster
2021-07-14 6:17 ` Dongli Zhang [this message]
2021-07-14 9:42 ` Markus Armbruster
2021-07-14 15:42 ` Dongli Zhang
2021-07-14 0:47 ` [PATCH v3 2/3] msix/hmp: add interface to dump device specific info Dongli Zhang
2021-07-14 0:47 ` [PATCH v3 3/3] virtio-pci/hmp: implement device specific hmp interface Dongli Zhang
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