Messages in this thread | | | Subject | Re: [PATCH] arm: KVM: fix possible misalignment of PGDs and bounce page | Date | Sat, 29 Mar 2014 14:01:57 +0000 | From | Marc Zyngier <> |
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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 <msalter@redhat.com> >> --- >> 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 <christoffer.dall@linaro.org> > > If Marc agrees I can queue this for -rc1.
Looks good to me indeed.
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
M. -- Fast, cheap, reliable. Pick two.
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