From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Roedel, Joerg" Subject: Re: Crash on kvm_iommu_map_pages Date: Mon, 1 Nov 2010 14:53:22 +0100 Message-ID: <20101101135322.GG20959@amd.com> References: <4CCEB7CF.8030207@web.de> <4CCEB946.7070103@web.de> <20101101132127.GF20959@amd.com> <4CCEBFAC.1000809@web.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: kvm , Sheng Yang , Linux Kernel Mailing List To: Jan Kiszka Return-path: Content-Disposition: inline In-Reply-To: <4CCEBFAC.1000809@web.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, Nov 01, 2010 at 09:25:00AM -0400, Jan Kiszka wrote: > Am 01.11.2010 14:21, Roedel, Joerg wrote: > > The registers rax and rbx contain non-canonical addresses (if > > interpreted as pointers). The instruction where this happens is a mov so > > I guess that the #GP is because of an non-canonical address. > > Can you find out the code-line where this happens and the exact > > assembler instruction? (haven't managed to decode the registers used). > > In pfn_to_dma_pte, line 710: > > if (!dma_pte_present(pte)) { > ffffffff8121de8c: f6 03 03 testb $0x3,(%rbx) > ffffffff8121de8f: 0f 85 d8 00 00 00 jne ffffffff8121df6d > > The first instruction raises the fault. Ok, so it seems that my understanding of the Code: field in the crash-message was wrong :) Anyway, the testb uses rbx as an address which has a non-canonical value. This means the the address of 'pte' is invalid. Since rax also contains a wrong address the 'parent' variable probably already contains the wrong address. Does the attached patch help? diff --git a/include/linux/dma_remapping.h b/include/linux/dma_remapping.h index 5619f85..ca46f24 100644 --- a/include/linux/dma_remapping.h +++ b/include/linux/dma_remapping.h @@ -6,7 +6,7 @@ */ #define VTD_PAGE_SHIFT (12) #define VTD_PAGE_SIZE (1UL << VTD_PAGE_SHIFT) -#define VTD_PAGE_MASK (((u64)-1) << VTD_PAGE_SHIFT) +#define VTD_PAGE_MASK ((((u64)-1) << VTD_PAGE_SHIFT) & ((1ULL << 52) - 1)) #define VTD_PAGE_ALIGN(addr) (((addr) + VTD_PAGE_SIZE - 1) & VTD_PAGE_MASK) #define DMA_PTE_READ (1) -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo, Andrew Bowd Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632