From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [Linux PATCH] Fix to hugepages to work around new PWT handling Date: Wed, 09 Jun 2010 11:21:45 -0700 Message-ID: <4C0FDBB9.8090807@goop.org> References: <20100609140252.18351.48175.sendpatchset@magnum.int.mccr.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100609140252.18351.48175.sendpatchset@magnum.int.mccr.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Dave McCracken Cc: Xen Developers List List-Id: xen-devel@lists.xenproject.org On 06/09/2010 07:02 AM, Dave McCracken wrote: > Recent changes to Linux include code to set new flags in the pte, > including _PAGE_PAT and _PAGE_PWT. That change conflicts with hugepage > using the pte macros to set up its pmd entries. This patch resolves > that problem. > Could you explain this a bit more clearly? Why is using __pmd not working in this case? Is it because the kernel is now setting PAT and PWT on huge pages? But PAT isn't even the same flag for huge pages... > An additional fix here is to make sure the _PAGE_PRESENT bit is set > before hugepages does a mk_pte(), since Xen depends on that bit to > trigger the pfn->mfn translation. > Why is the kernel creating a non-present mapping? If it isn't present, why does it matter whether we do the pfn->mfn conversion? J > Signed-off-by: Dave McCracken > > -------- > > > --- stable-2.6.32.x//arch/x86/include/asm/hugetlb.h 2010-06-04 12:19:31.000000000 -0500 > +++ 2.6.32-hfix//arch/x86/include/asm/hugetlb.h 2010-06-08 12:23:53.000000000 -0500 > @@ -44,7 +44,7 @@ static inline pte_t huge_ptep_get(pte_t > static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, pte_t pte) > { > - set_pmd((pmd_t *)ptep, __pmd(pte_val(pte))); > + set_pmd((pmd_t *)ptep, native_make_pmd(native_pte_val(pte))); > } > > static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm, > --- stable-2.6.32.x//mm/hugetlb.c 2010-06-04 12:19:36.000000000 -0500 > +++ 2.6.32-hfix//mm/hugetlb.c 2010-06-07 07:11:34.000000000 -0500 > @@ -1732,12 +1732,14 @@ static pte_t make_huge_pte(struct vm_are > int writable) > { > pte_t entry; > + pgprot_t pgprot; > > + pgprot = __pgprot(pgprot_val(vma->vm_page_prot) | _PAGE_PRESENT); > if (writable) { > entry = > - pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot))); > + pte_mkwrite(pte_mkdirty(mk_pte(page, pgprot))); > } else { > - entry = huge_pte_wrprotect(mk_pte(page, vma->vm_page_prot)); > + entry = huge_pte_wrprotect(mk_pte(page, pgprot)); > } > entry = pte_mkyoung(entry); > entry = pte_mkhuge(entry); > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > >