Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753371AbaDYRCM (ORCPT ); Fri, 25 Apr 2014 13:02:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:30216 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752819AbaDYRCJ (ORCPT ); Fri, 25 Apr 2014 13:02:09 -0400 Message-ID: <1398445293.3010.77.camel@deneb.redhat.com> Subject: Re: [PATCH] arm: KVM: fix possible misalignment of PGDs and bounce page From: Mark Salter To: Marc Zyngier Cc: Christoffer Dall , kvmarm@lists.cs.columbia.edu, Russell King , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org Date: Fri, 25 Apr 2014 13:01:33 -0400 In-Reply-To: References: <1396016719-13807-1-git-send-email-msalter@redhat.com> <20140328193733.GL25519@cbox> Organization: Red Hat, Inc Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ping. Can we get this into 3.15rc as a bug fix? Anything I can help with? --Mark On Sat, 2014-03-29 at 14:01 +0000, Marc Zyngier wrote: > On 2014-03-28 19:37, Christoffer Dall wrote: > > On Fri, Mar 28, 2014 at 10:25:19AM -0400, Mark Salter wrote: > >> The kvm/mmu code shared by arm and arm64 uses kalloc() to allocate > >> a bounce page (if hypervisor init code crosses page boundary) and > >> hypervisor PGDs. The problem is that kalloc() does not guarantee > >> the proper alignment. In the case of the bounce page, the page sized > >> buffer allocated may also cross a page boundary negating the purpose > >> and leading to a hang during kvm initialization. Likewise the PGDs > >> allocated may not meet the minimum alignment requirements of the > >> underlying MMU. This patch uses __get_free_page() to guarantee the > >> worst case alignment needs of the bounce page and PGDs on both arm > >> and arm64. > >> > >> Signed-off-by: Mark Salter > >> --- > >> arch/arm/kvm/mmu.c | 15 +++++++++------ > >> 1 file changed, 9 insertions(+), 6 deletions(-) > >> > >> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > >> index 7789857..575d790 100644 > >> --- a/arch/arm/kvm/mmu.c > >> +++ b/arch/arm/kvm/mmu.c > >> @@ -42,6 +42,8 @@ static unsigned long hyp_idmap_start; > >> static unsigned long hyp_idmap_end; > >> static phys_addr_t hyp_idmap_vector; > >> > >> +#define pgd_order get_order(PTRS_PER_PGD * sizeof(pgd_t)) > >> + > >> #define kvm_pmd_huge(_x) (pmd_huge(_x) || pmd_trans_huge(_x)) > >> > >> static void kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t > >> ipa) > >> @@ -199,14 +201,14 @@ void free_boot_hyp_pgd(void) > >> if (boot_hyp_pgd) { > >> unmap_range(NULL, boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE); > >> unmap_range(NULL, boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE); > >> - kfree(boot_hyp_pgd); > >> + free_pages((unsigned long)boot_hyp_pgd, pgd_order); > >> boot_hyp_pgd = NULL; > >> } > >> > >> if (hyp_pgd) > >> unmap_range(NULL, hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE); > >> > >> - kfree(init_bounce_page); > >> + free_page((unsigned long)init_bounce_page); > >> init_bounce_page = NULL; > >> > >> mutex_unlock(&kvm_hyp_pgd_mutex); > >> @@ -236,7 +238,7 @@ void free_hyp_pgds(void) > >> for (addr = VMALLOC_START; is_vmalloc_addr((void*)addr); addr += > >> PGDIR_SIZE) > >> unmap_range(NULL, hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE); > >> > >> - kfree(hyp_pgd); > >> + free_pages((unsigned long)hyp_pgd, pgd_order); > >> hyp_pgd = NULL; > >> } > >> > >> @@ -930,7 +932,7 @@ int kvm_mmu_init(void) > >> size_t len = __hyp_idmap_text_end - __hyp_idmap_text_start; > >> phys_addr_t phys_base; > >> > >> - init_bounce_page = kmalloc(PAGE_SIZE, GFP_KERNEL); > >> + init_bounce_page = (void *)__get_free_page(GFP_KERNEL); > >> if (!init_bounce_page) { > >> kvm_err("Couldn't allocate HYP init bounce page\n"); > >> err = -ENOMEM; > >> @@ -956,8 +958,9 @@ int kvm_mmu_init(void) > >> (unsigned long)phys_base); > >> } > >> > >> - hyp_pgd = kzalloc(PTRS_PER_PGD * sizeof(pgd_t), GFP_KERNEL); > >> - boot_hyp_pgd = kzalloc(PTRS_PER_PGD * sizeof(pgd_t), GFP_KERNEL); > >> + hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, > >> pgd_order); > >> + boot_hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, > >> pgd_order); > >> + > >> if (!hyp_pgd || !boot_hyp_pgd) { > >> kvm_err("Hyp mode PGD not allocated\n"); > >> err = -ENOMEM; > >> -- > >> 1.8.5.3 > >> > > This looks right to me. Funnily enough I seem to remember a > > discussion > > from when we originally merged this code where someone (maybe me) > > argued > > that kmalloc() would align to the size of the allocation, but I don't > > see anything backing this up at this point. > > > > So: > > > > Acked-by: Christoffer Dall > > > > If Marc agrees I can queue this for -rc1. > > Looks good to me indeed. > > Acked-by: Marc Zyngier > > M. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/