From: Dexuan Cui <decui@microsoft.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>, Rik van Riel <riel@redhat.com>,
        "H. Peter Anvin" <hpa@linux.intel.com>
CC: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Does slow_virt_to_phys() work with vmalloc() in the case of
 32bit-PAE and 2MB page?
Thread-Topic: Does slow_virt_to_phys() work with vmalloc() in the case of
 32bit-PAE and 2MB page?
Thread-Index: Ac/yfEPZo4Dur33tTNaXzR8m0tIt+Q==
Date: Tue, 28 Oct 2014 07:08:04 +0000
Message-ID: <F792CF86EFE20D4AB8064279AFBA51C610567A76@HKNPRD3002MB017.064d.mgd.msft.net>
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Hi all,
I suspect slow_virt_to_phys() may not work with vmalloc() in
the 32-bit PAE case(when the pa > 4GB), probably due to 2MB page(?)

Is there any known issue with slow_virt_to_phys() + vmalloc() +
32-bit PAE + 2MB page?

>From what I read the code of slow_virt_to_phys(), the variable 'psize' is
assigned with a value but not used at all -- is this a bug?


phys_addr_t slow_virt_to_phys(void *__virt_addr)
{
        unsigned long virt_addr = (unsigned long)__virt_addr;
        phys_addr_t phys_addr;
        unsigned long offset;
        enum pg_level level;
        unsigned long psize;
        unsigned long pmask;
        pte_t *pte;

        pte = lookup_address(virt_addr, &level);
        BUG_ON(!pte);
        psize = page_level_size(level);
        pmask = page_level_mask(level);
        offset = virt_addr & ~pmask;
        phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
        return (phys_addr | offset);
}

Thanks,
-- Dexuan

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