Re: [PATCH v4 18/30] KVM: x86: Move "struct kvm_x86_msr_filter" definition to msrs.c

[Binbin Wu <binbin.wu@linux.intel.com>]

On 6/16/2026 3:29 PM, Huang, Kai wrote:
> On Tue, 2026-06-16 at 14:29 +0800, Binbin Wu wrote:
>> On 6/13/2026 8:03 AM, Sean Christopherson wrote:
>>> Move the definition of "struct kvm_x86_msr_filter" and its associate,
>>> "struct msr_bitmap_range", to msrs.c, as the details of the filters are
>>> very much implementation details that can and should be buried in msrs.c.
>>> While the _existence_ of filters is public knowledge, almost by definition,
>>> the contents don't need to be exposed outside of the MSR code as the filter
>>> data is provided by userspace, i.e. it pretty much has to be dynamically
>>> allocated, and thus never should be fully embedded in a globally visible
>>> structure.
>>>
>>> Note, this creates a discrepancy with the PMU event filter structure; that
>>> will be remedied shortly.
>>>
>>> No functional change intended.
>>>
>>> Suggested-by: Kai Huang <kai.huang@intel.com>
>>> Signed-off-by: Sean Christopherson <seanjc@google.com>
>>> ---
>>>  arch/x86/include/asm/kvm_host.h | 15 ++-------------
>>>  arch/x86/kvm/msrs.c             | 13 +++++++++++++
>>>  2 files changed, 15 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>>> index 09e437c947a9..4ff6304c02d0 100644
>>> --- a/arch/x86/include/asm/kvm_host.h
>>> +++ b/arch/x86/include/asm/kvm_host.h
>>> @@ -315,6 +315,8 @@ enum x86_intercept_stage;
>>>  struct kvm_kernel_irqfd;
>>>  struct kvm_kernel_irq_routing_entry;
>>>  
>>> +struct kvm_x86_msr_filter;
>>
>>
>> Just FYI, the code failed to build on my desktop with an old gcc version v9.4.
>> Due to dereferencing pointer to incomplete type ‘struct kvm_x86_msr_filter' via
>> typeof().
>>
>> It's not the fault of the patch, the issue was fixed for GCC 10+ according to
>> the link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44257
> 
> This issue was reported at:
> 
> 	rusty 2010-05-24 00:29:46 UTC
> 
> But only got fixed at:
> 
> 	Drea Pinski 2021-09-20 02:14:38 UTC
> 
> Amazing :-)
> 
>>
>> But the minimal tool version got for gcc is still v8.1.0, not sure if it needs
>> to bump the version in scripts/min-tool-version.sh?
>>
> 
> Bumping the version would have global impact, so I don't think we should do.
> 
> However, does moving the structure definition to "msrs.h" fix the problem?

Yes, it does.

Similar issue for struct kvm_x86_pmu_event_filter also could be resolved
by moving the structure definition to "pmu.h"