On 2014-03-28 19:37, Christoffer Dall wrote:

On Fri, Mar 28, 2014 at 10:25:19AM -0400, Mark Salter wrote:

quoted

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 <redacted>
---
 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 <redacted>

If Marc agrees I can queue this for -rc1.

Looks good to me indeed.

Acked-by: Marc Zyngier <redacted>

         M.
-- 
Fast, cheap, reliable. Pick two.