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Date: Sun, 20 Sep 2009 12:35:19 +0300 From: "Kirill A. Shutemov" <kirill@...temov.name> To: Russell King - ARM Linux <linux@....linux.org.uk> Cc: Bityutskiy Artem <Artem.Bityutskiy@...ia.com>, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, Koskinen Aaro <aaro.koskinen@...ia.com> Subject: Re: [PATCH 1/2] ARM: Pass IFSR register to do_PrefetchAbort() On Sun, Sep 20, 2009 at 11:15 AM, Russell King - ARM Linux <linux@....linux.org.uk> wrote: > On Sat, Sep 19, 2009 at 12:03:16PM +0100, Russell King - ARM Linux wrote: >> On Fri, Sep 18, 2009 at 11:55:42PM +0300, Kirill A. Shutemov wrote: >> > It needed for proper prefetch abort handling on ARMv7. >> >> I think the only thing which is missing is an explaination about why >> this is desirable given that only later CPUs can give this additional >> information. > > So you've posted it to the patch system, without further discussion here. > > I think the solution is wrong - it makes instruction permission faults > unnecessarily noisy, which is not what the decoding table is supposed > to be doing. The decoding table's bad entries are there to catch those > _unexpected_ cases. > > Instead, I suggest that you have a look at this: > > if (fsr & (1 << 11)) /* write? */ > mask = VM_WRITE; > else > mask = VM_READ|VM_EXEC|VM_WRITE; > > fault = VM_FAULT_BADACCESS; > if (!(vma->vm_flags & mask)) > goto out; > > in __do_page_fault - if we are handling a prefetch abort, we really only > want to check that the VMA has VM_EXEC permission, not that it can be > read and written as well. > Ok, so __do_page_fault() should know where we are: in data abort or in prefetch abort. What is right way to do it? Should we create one more argument or use one of reserved bits IFSR? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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