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[7/9] KVM: arm64: Do not try to map PUDs when they are folded into PMD

Message ID 20200904104530.1082676-8-maz@kernel.org
State New, archived
Headers show
Series [GIT,PULL] KVM/arm64 fixes for 5.9 | expand

Commit Message

Marc Zyngier Sept. 4, 2020, 10:45 a.m. UTC
For the obscure cases where PMD and PUD are the same size
(64kB pages with 42bit VA, for example, which results in only
two levels of page tables), we can't map anything as a PUD,
because there is... erm... no PUD to speak of. Everything is
either a PMD or a PTE.

So let's only try and map a PUD when its size is different from
that of a PMD.

Cc: stable@vger.kernel.org
Fixes: b8e0ba7c8bea ("KVM: arm64: Add support for creating PUD hugepages at stage 2")
Reported-by: Gavin Shan <gshan@redhat.com>
Reported-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/mmu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Punit Agrawal Sept. 9, 2020, 3:23 a.m. UTC | #1
Hi Marc,

Noticed this patch while catching up with the lists.

Marc Zyngier <maz@kernel.org> writes:

> For the obscure cases where PMD and PUD are the same size
> (64kB pages with 42bit VA, for example, which results in only
> two levels of page tables), we can't map anything as a PUD,
> because there is... erm... no PUD to speak of. Everything is
> either a PMD or a PTE.
>
> So let's only try and map a PUD when its size is different from
> that of a PMD.
>
> Cc: stable@vger.kernel.org
> Fixes: b8e0ba7c8bea ("KVM: arm64: Add support for creating PUD hugepages at stage 2")
> Reported-by: Gavin Shan <gshan@redhat.com>
> Reported-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Eric Auger <eric.auger@redhat.com>
> Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/mmu.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 0121ef2c7c8d..16b8660ddbcc 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1964,7 +1964,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  		(fault_status == FSC_PERM &&
>  		 stage2_is_exec(mmu, fault_ipa, vma_pagesize));
>  
> -	if (vma_pagesize == PUD_SIZE) {
> +	/*
> +	 * If PUD_SIZE == PMD_SIZE, there is no real PUD level, and
> +	 * all we have is a 2-level page table. Trying to map a PUD in
> +	 * this case would be fatally wrong.
> +	 */
> +	if (PUD_SIZE != PMD_SIZE && vma_pagesize == PUD_SIZE) {
>  		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
>  
>  		new_pud = kvm_pud_mkhuge(new_pud);

Good catch!
Missed the 64kb / 42b VA case while adding the initial support.

Thanks for fixing it.

Punit
diff mbox series

Patch

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 0121ef2c7c8d..16b8660ddbcc 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1964,7 +1964,12 @@  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		(fault_status == FSC_PERM &&
 		 stage2_is_exec(mmu, fault_ipa, vma_pagesize));
 
-	if (vma_pagesize == PUD_SIZE) {
+	/*
+	 * If PUD_SIZE == PMD_SIZE, there is no real PUD level, and
+	 * all we have is a 2-level page table. Trying to map a PUD in
+	 * this case would be fatally wrong.
+	 */
+	if (PUD_SIZE != PMD_SIZE && vma_pagesize == PUD_SIZE) {
 		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
 
 		new_pud = kvm_pud_mkhuge(new_pud);