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Re: [PATCH v4] vfio/common: remove spurious tpm-crb-cmd misalignment war
From: |
Cornelia Huck |
Subject: |
Re: [PATCH v4] vfio/common: remove spurious tpm-crb-cmd misalignment warning |
Date: |
Fri, 06 May 2022 09:56:42 +0200 |
User-agent: |
Notmuch/0.34 (https://notmuchmail.org) |
On Fri, May 06 2022, Eric Auger <eric.auger@redhat.com> wrote:
> Hi Connie,
>
> On 5/6/22 09:34, Cornelia Huck wrote:
>> On Fri, May 06 2022, Eric Auger <eric.auger@redhat.com> wrote:
>>
>>> Hi Alex,
>>>
>>> On 4/28/22 22:14, Alex Williamson wrote:
>>>> On Thu, 28 Apr 2022 15:49:45 +0200
>>>> Eric Auger <eric.auger@redhat.com> wrote:
>>>>> +static bool vfio_known_safe_misalignment(MemoryRegionSection *section)
>>>>> +{
>>>>> + MemoryRegion *mr = section->mr;
>>>>> +
>>>>> + if (!TPM_IS_CRB(mr->owner)) {
>>>>> + return false;
>>>>> + }
>>>> It looks like this test is going to need to be wrapped in #ifdef
>>>> CONFIG_TPM:
>>> sorry for the delay. Your message fell though the cracks :-(
>>>
>>> if I put an '#ifdef CONFIG_TPM' I need to inverse the logic because by
>>> default the function shall return false.
>>>
>>> solution #1
>>>
>>> #ifdef CONFIG_TPM
>>> if (TPM_IS_CRB(mr->owner)) {
>>>
>>> /* this is a known safe misaligned region, just trace for debug purpose
>>> */
>>> trace_vfio_known_safe_misalignment(memory_region_name(mr),
>>> section->offset_within_address_space,
>>> section->offset_within_region,
>>> qemu_real_host_page_size());
>>>
>>> return true;
>>> }
>>>
>>> #endif
>>> return false;
>>>
>>> This looks weird to me.
>>>
>>> + if (!object_dynamic_cast(mr->owner, TYPE_TPM_CRB)) {
>>> + return false;
>>> + }
>>>
>>>
>>> solution #2
>>> replace !object_dynamic_cast(mr->owner, TYPE_TPM_CRB) by
>>> !object_dynamic_cast(mr->owner, "tpm-crb")
>>> and add a comment saying that we don't use TYPE_TPM_CRB on purpose
>>>
>>> solution #3
>>> Move #define TPM_IS_CRB(chr) and related defined out of
>>> #ifdef CONFIG_TPM hoping it does not have other side effects
>>>
>>> Thoughts?
>>> Eric
>> solution #4
>>
>> #ifndef CONFIG_TPM
>> /* needed for an alignment check in non-tpm code */
>> static inline Object *TPM_IS_CRB(Object *obj)
>> {
>> return NULL;
>> }
>> #endif
>>
>> I think it would be good if we could hide the configuration details in
>> the header.
>>
> Yep, I forgot to mention solution #3 also happened in include/sysemu/tpm.h.
> Connie, either we add your stub function or we move the following out of
> the #ifdef CONFIG_TPM. This should be harmless, no?
> Stefan, any preference?
>
> #define TYPE_TPM_TIS_ISA "tpm-tis"
> #define TYPE_TPM_TIS_SYSBUS "tpm-tis-device"
> #define TYPE_TPM_CRB "tpm-crb"
> #define TYPE_TPM_SPAPR "tpm-spapr"
>
> #define TPM_IS_TIS_ISA(chr) \
> object_dynamic_cast(OBJECT(chr), TYPE_TPM_TIS_ISA)
> #define TPM_IS_TIS_SYSBUS(chr) \
> object_dynamic_cast(OBJECT(chr), TYPE_TPM_TIS_SYSBUS)
> #define TPM_IS_CRB(chr) \
> object_dynamic_cast(OBJECT(chr), TYPE_TPM_CRB)
> #define TPM_IS_SPAPR(chr) \
> object_dynamic_cast(OBJECT(chr), TYPE_TPM_SPAPR)
If it's just those simple defines, I can't see how that could break
things (you won't have the respective objects anyway). So yes, I think
that is the best solution.