From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v4] arm64: fix VTTBR_BADDR_MASK Date: Tue, 19 Aug 2014 17:14:12 +0200 Message-ID: <20140819151412.GG31086@cbox> References: <20140811203823.2828.36074.stgit@joelaarch64.amd.com> <20140812160521.GO10550@cbox> <53F26282.5010103@amd.com> <20140819122236.GB31086@cbox> <53F35995.8010008@amd.com> <20140819143752.GD31086@cbox> <53F364FF.8040903@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, jungseoklee85@gmail.com, Sungjinn Chung , Jungseok Lee To: Joel Schopp Return-path: Received: from mail-la0-f50.google.com ([209.85.215.50]:59365 "EHLO mail-la0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751810AbaHSPOA (ORCPT ); Tue, 19 Aug 2014 11:14:00 -0400 Received: by mail-la0-f50.google.com with SMTP id pi18so6027410lab.37 for ; Tue, 19 Aug 2014 08:13:58 -0700 (PDT) Content-Disposition: inline In-Reply-To: <53F364FF.8040903@amd.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Aug 19, 2014 at 09:53:51AM -0500, Joel Schopp wrote: > > On 08/19/2014 09:37 AM, Christoffer Dall wrote: > > On Tue, Aug 19, 2014 at 09:05:09AM -0500, Joel Schopp wrote: > >> On 08/19/2014 07:22 AM, Christoffer Dall wrote: > >>> On Mon, Aug 18, 2014 at 03:30:58PM -0500, Joel Schopp wrote: > >>>> #endif /* __ARM_KVM_MMU_H__ */ > >>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > >>>> index 16e7994..70f0f02 100644 > >>>> --- a/arch/arm/kvm/mmu.c > >>>> +++ b/arch/arm/kvm/mmu.c > >>>> @@ -521,6 +521,7 @@ int create_hyp_io_mappings(void *from, void *to, phys_addr_t phys_addr) > >>>> */ > >>>> int kvm_alloc_stage2_pgd(struct kvm *kvm) > >>>> { > >>>> + unsigned int s2_pgds, s2_pgd_order; > >>>> pgd_t *pgd; > >>>> > >>>> if (kvm->arch.pgd != NULL) { > >>>> @@ -528,10 +529,18 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm) > >>>> return -EINVAL; > >>>> } > >>>> > >>>> - pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, S2_PGD_ORDER); > >>>> + s2_pgds = (1 << (kvm_get_phys_addr_shift() - PGDIR_SHIFT)); > >>>> + s2_pgd_order = get_order(s2_pgds * sizeof(pgd_t)); > >>>> + > >>>> + pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, s2_pgd_order); > >>>> if (!pgd) > >>>> return -ENOMEM; > >>>> > >>>> + if ((unsigned long)pgd & ~vttbr_baddr_mask) { > >>>> + kvm_err("Stage-2 pgd not correctly aligned: %p\n", pgd); > >>>> + return -EFAULT; > >>>> + } > >>>> > >>>> > >>>> There are two problems that I've found here. The first problem is that > >>>> vttbr_baddr_mask isn't allocated yet at this point in the code. > >>> allocated? you mean assigned? > >>> aren't you setting vttbr_baddr_mask in kvm_arch_init()? that's > >>> certainly called before kvm_arch_init_vm(). > >> Yes, I mean assigned, at least I got the first letter correct :) All I > >> know is that vttbr_baddr_mask was still zero and checking for zero and > >> calling the set function gave it a value. > > that sounds.... weird and wrong. Hum. Mind sticking a few prints in > > there and figuring out what's causing this? > > > >>> > >>>> The > >>>> second problem is that pgd is a virtual address, ie pgd == > >>>> 0xfffffe03bbb40000 while the vttbr masks off the high bits for a > >>>> physical address, ie vttbr_baddr_mask=0x00007ffffffe0000 . Even > >>>> correcting for those issues I haven't been able to make this check work > >>>> properly. I'll resend v5 the patch with all the other suggested changes. > >>>> > >>> What are the issues that you face? Iow. what is the alignment of the > >>> returned physical address? > >>> > >>> (You should be able to just to virt_to_phys(pgd) and use that to test > >>> for the vttbr_baddr_mask). > >> The addresses above are actually from my system, 64K page aligned on a > >> 64K page kernel. I did use virt_to_phys() and the kernel got a null > >> dereference and paniced, I didn't trace down where the panic was occuring. > >> > > virt_to_phys() directly caused the null dereference? That sounds bad! > I don't think it was the virt_to_phys() directly causing the null > dereference, but again I didn't trace it down. > > > > > Would you mind trying to trace this down? I'll be happy to provide as > > much help as I can along the way. > I can break the kvm_alloc_stage2_pgd check into a separate patch on top > of this one and circle back around to it after I finish another > unrelated thing I'm working on. that would be great, thanks.