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Date: Mon, 31 Mar 2014 00:23:35 +0100 From: Ben Hutchings <ben@...adent.org.uk> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org CC: akpm@...ux-foundation.org, "Mahesh Salgaonkar" <mahesh@...ux.vnet.ibm.com>, "Benjamin Herrenschmidt" <benh@...nel.crashing.org>, "Laurent Dufour" <ldufour@...ux.vnet.ibm.com> Subject: [PATCH 3.2 154/200] powerpc/crashdump : Fix page frame number check in copy_oldmem_page 3.2.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Laurent Dufour <ldufour@...ux.vnet.ibm.com> commit f5295bd8ea8a65dc5eac608b151386314cb978f1 upstream. In copy_oldmem_page, the current check using max_pfn and min_low_pfn to decide if the page is backed or not, is not valid when the memory layout is not continuous. This happens when running as a QEMU/KVM guest, where RTAS is mapped higher in the memory. In that case max_pfn points to the end of RTAS, and a hole between the end of the kdump kernel and RTAS is not backed by PTEs. As a consequence, the kdump kernel is crashing in copy_oldmem_page when accessing in a direct way the pages in that hole. This fix relies on the memblock's service memblock_is_region_memory to check if the read page is part or not of the directly accessible memory. Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com> Tested-by: Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org> Signed-off-by: Ben Hutchings <ben@...adent.org.uk> --- arch/powerpc/kernel/crash_dump.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/arch/powerpc/kernel/crash_dump.c +++ b/arch/powerpc/kernel/crash_dump.c @@ -108,17 +108,19 @@ ssize_t copy_oldmem_page(unsigned long p size_t csize, unsigned long offset, int userbuf) { void *vaddr; + phys_addr_t paddr; if (!csize) return 0; csize = min_t(size_t, csize, PAGE_SIZE); + paddr = pfn << PAGE_SHIFT; - if ((min_low_pfn < pfn) && (pfn < max_pfn)) { - vaddr = __va(pfn << PAGE_SHIFT); + if (memblock_is_region_memory(paddr, csize)) { + vaddr = __va(paddr); csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf); } else { - vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0); + vaddr = __ioremap(paddr, PAGE_SIZE, 0); csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf); iounmap(vaddr); } -- 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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