linux-kernel - Re: [PATCH V6 01/16] perf/core: Add PERF_SAMPLE_DATA_PAGE

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Message-ID: <28c9fe5b-a19f-2d12-cf5a-83b1b36c37ed@intel.com>
Date:   Wed, 12 Aug 2020 06:53:39 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, eranian@...gle.com, ak@...ux.intel.com,
        kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH V6 01/16] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE

On 8/12/20 6:39 AM, Liang, Kan wrote:
> I searched the vma_mmu_pagesize(). It seems that PowerPC is the only
> one that defines a 'strong' function. In other words, the MMUPageSize
> and KerelPageSize are the same for X86. However, it seems not true
> for the above compound page cases. Is it a bug for smaps? Or am I
> missed anything?

__weak unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
{
        return vma_kernel_pagesize(vma);
}

unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
{
        if (vma->vm_ops && vma->vm_ops->pagesize)
                return vma->vm_ops->pagesize(vma);
        return PAGE_SIZE;
}

It can be overridden with vm_ops too, not just a weak symbol.