diff mbox series

[v9,2/8] KVM: arm/arm64: Re-factor setting the Stage 2 entry to exec on fault

Message ID 20181031175745.18650-3-punit.agrawal@arm.com (mailing list archive)
State New, archived
Headers show
Series KVM: Support PUD hugepage at stage 2 | expand

Commit Message

Punit Agrawal Oct. 31, 2018, 5:57 p.m. UTC 
Stage 2 fault handler marks a page as executable if it is handling an
execution fault or if it was a permission fault in which case the
executable bit needs to be preserved.

The logic to decide if the page should be marked executable is
duplicated for PMD and PTE entries. To avoid creating another copy
when support for PUD hugepages is introduced refactor the code to
share the checks needed to mark a page table entry as executable.

Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
 virt/kvm/arm/mmu.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

Comments

Anshuman Khandual Dec. 3, 2018, 1:32 p.m. UTC | #1 
On 10/31/2018 11:27 PM, Punit Agrawal wrote:
> Stage 2 fault handler marks a page as executable if it is handling an
> execution fault or if it was a permission fault in which case the
> executable bit needs to be preserved.
> 
> The logic to decide if the page should be marked executable is
> duplicated for PMD and PTE entries. To avoid creating another copy
> when support for PUD hugepages is introduced refactor the code to
> share the checks needed to mark a page table entry as executable.
> 
> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Christoffer Dall <christoffer.dall@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  virt/kvm/arm/mmu.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index 59595207c5e1..6912529946fb 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1475,7 +1475,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  			  unsigned long fault_status)
>  {
>  	int ret;
> -	bool write_fault, exec_fault, writable, force_pte = false;
> +	bool write_fault, writable, force_pte = false;
> +	bool exec_fault, needs_exec;

New line not required, still within 80 characters.

>  	unsigned long mmu_seq;
>  	gfn_t gfn = fault_ipa >> PAGE_SHIFT;
>  	struct kvm *kvm = vcpu->kvm;
> @@ -1598,19 +1599,25 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (exec_fault)
>  		invalidate_icache_guest_page(pfn, vma_pagesize);
>  
> +	/*
> +	 * If we took an execution fault we have made the
> +	 * icache/dcache coherent above and should now let the s2

Coherent or invalidated with invalidate_icache_guest_page ?

> +	 * mapping be executable.
> +	 *
> +	 * Write faults (!exec_fault && FSC_PERM) are orthogonal to
> +	 * execute permissions, and we preserve whatever we have.
> +	 */

Otherwise looks good.
Suzuki K Poulose Dec. 5, 2018, 10:47 a.m. UTC | #2 
On 03/12/2018 13:32, Anshuman Khandual wrote:
> 
> 
> On 10/31/2018 11:27 PM, Punit Agrawal wrote:
>> Stage 2 fault handler marks a page as executable if it is handling an
>> execution fault or if it was a permission fault in which case the
>> executable bit needs to be preserved.
>>
>> The logic to decide if the page should be marked executable is
>> duplicated for PMD and PTE entries. To avoid creating another copy
>> when support for PUD hugepages is introduced refactor the code to
>> share the checks needed to mark a page table entry as executable.
>>
>> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Cc: Christoffer Dall <christoffer.dall@arm.com>
>> Cc: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>>   virt/kvm/arm/mmu.c | 28 +++++++++++++++-------------
>>   1 file changed, 15 insertions(+), 13 deletions(-)
>>
>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>> index 59595207c5e1..6912529946fb 100644
>> --- a/virt/kvm/arm/mmu.c
>> +++ b/virt/kvm/arm/mmu.c
>> @@ -1475,7 +1475,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   			  unsigned long fault_status)
>>   {
>>   	int ret;
>> -	bool write_fault, exec_fault, writable, force_pte = false;
>> +	bool write_fault, writable, force_pte = false;
>> +	bool exec_fault, needs_exec;
> 
> New line not required, still within 80 characters.
> 
>>   	unsigned long mmu_seq;
>>   	gfn_t gfn = fault_ipa >> PAGE_SHIFT;
>>   	struct kvm *kvm = vcpu->kvm;
>> @@ -1598,19 +1599,25 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	if (exec_fault)
>>   		invalidate_icache_guest_page(pfn, vma_pagesize);
>>   
>> +	/*
>> +	 * If we took an execution fault we have made the
>> +	 * icache/dcache coherent above and should now let the s2
> 
> Coherent or invalidated with invalidate_icache_guest_page ?

We also do clean_dcache above if needed. So that makes sure
the data is coherent. Am I missing something here ?

> 
>> +	 * mapping be executable.
>> +	 *
>> +	 * Write faults (!exec_fault && FSC_PERM) are orthogonal to
>> +	 * execute permissions, and we preserve whatever we have.
>> +	 */
> 
> Otherwise looks good.
> 


Suzuki
Christoffer Dall Dec. 10, 2018, 8:59 a.m. UTC | #3 
On Mon, Dec 03, 2018 at 07:02:23PM +0530, Anshuman Khandual wrote:
> 
> 
> On 10/31/2018 11:27 PM, Punit Agrawal wrote:
> > Stage 2 fault handler marks a page as executable if it is handling an
> > execution fault or if it was a permission fault in which case the
> > executable bit needs to be preserved.
> > 
> > The logic to decide if the page should be marked executable is
> > duplicated for PMD and PTE entries. To avoid creating another copy
> > when support for PUD hugepages is introduced refactor the code to
> > share the checks needed to mark a page table entry as executable.
> > 
> > Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> > Cc: Christoffer Dall <christoffer.dall@arm.com>
> > Cc: Marc Zyngier <marc.zyngier@arm.com>
> > ---
> >  virt/kvm/arm/mmu.c | 28 +++++++++++++++-------------
> >  1 file changed, 15 insertions(+), 13 deletions(-)
> > 
> > diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> > index 59595207c5e1..6912529946fb 100644
> > --- a/virt/kvm/arm/mmu.c
> > +++ b/virt/kvm/arm/mmu.c
> > @@ -1475,7 +1475,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> >  			  unsigned long fault_status)
> >  {
> >  	int ret;
> > -	bool write_fault, exec_fault, writable, force_pte = false;
> > +	bool write_fault, writable, force_pte = false;
> > +	bool exec_fault, needs_exec;
> 
> New line not required, still within 80 characters.
> 

He's trying to logically group the two variables.  I don't see a problem
with that.


Thanks,

    Christoffer
Christoffer Dall Dec. 10, 2018, 9 a.m. UTC | #4 
On Wed, Dec 05, 2018 at 10:47:10AM +0000, Suzuki K Poulose wrote:
> 
> 
> On 03/12/2018 13:32, Anshuman Khandual wrote:
> >
> >
> >On 10/31/2018 11:27 PM, Punit Agrawal wrote:
> >>Stage 2 fault handler marks a page as executable if it is handling an
> >>execution fault or if it was a permission fault in which case the
> >>executable bit needs to be preserved.
> >>
> >>The logic to decide if the page should be marked executable is
> >>duplicated for PMD and PTE entries. To avoid creating another copy
> >>when support for PUD hugepages is introduced refactor the code to
> >>share the checks needed to mark a page table entry as executable.
> >>
> >>Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> >>Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> >>Cc: Christoffer Dall <christoffer.dall@arm.com>
> >>Cc: Marc Zyngier <marc.zyngier@arm.com>
> >>---
> >>  virt/kvm/arm/mmu.c | 28 +++++++++++++++-------------
> >>  1 file changed, 15 insertions(+), 13 deletions(-)
> >>
> >>diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> >>index 59595207c5e1..6912529946fb 100644
> >>--- a/virt/kvm/arm/mmu.c
> >>+++ b/virt/kvm/arm/mmu.c
> >>@@ -1475,7 +1475,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> >>  			  unsigned long fault_status)
> >>  {
> >>  	int ret;
> >>-	bool write_fault, exec_fault, writable, force_pte = false;
> >>+	bool write_fault, writable, force_pte = false;
> >>+	bool exec_fault, needs_exec;
> >
> >New line not required, still within 80 characters.
> >
> >>  	unsigned long mmu_seq;
> >>  	gfn_t gfn = fault_ipa >> PAGE_SHIFT;
> >>  	struct kvm *kvm = vcpu->kvm;
> >>@@ -1598,19 +1599,25 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> >>  	if (exec_fault)
> >>  		invalidate_icache_guest_page(pfn, vma_pagesize);
> >>+	/*
> >>+	 * If we took an execution fault we have made the
> >>+	 * icache/dcache coherent above and should now let the s2
> >
> >Coherent or invalidated with invalidate_icache_guest_page ?
> 
> We also do clean_dcache above if needed. So that makes sure
> the data is coherent. Am I missing something here ?
> 

I think you've got it right.  We have made the icache coherent with the
data/instructions in the page by invalidating the icache.  I think the
comment is ok either way.

Thanks,

    Christoffer
diff mbox series

Patch

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 59595207c5e1..6912529946fb 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1475,7 +1475,8 @@  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			  unsigned long fault_status)
 {
 	int ret;
-	bool write_fault, exec_fault, writable, force_pte = false;
+	bool write_fault, writable, force_pte = false;
+	bool exec_fault, needs_exec;
 	unsigned long mmu_seq;
 	gfn_t gfn = fault_ipa >> PAGE_SHIFT;
 	struct kvm *kvm = vcpu->kvm;
@@ -1598,19 +1599,25 @@  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (exec_fault)
 		invalidate_icache_guest_page(pfn, vma_pagesize);
 
+	/*
+	 * If we took an execution fault we have made the
+	 * icache/dcache coherent above and should now let the s2
+	 * mapping be executable.
+	 *
+	 * Write faults (!exec_fault && FSC_PERM) are orthogonal to
+	 * execute permissions, and we preserve whatever we have.
+	 */
+	needs_exec = exec_fault ||
+		(fault_status == FSC_PERM && stage2_is_exec(kvm, fault_ipa));
+
 	if (vma_pagesize == PMD_SIZE) {
 		pmd_t new_pmd = pfn_pmd(pfn, mem_type);
 		new_pmd = pmd_mkhuge(new_pmd);
 		if (writable)
 			new_pmd = kvm_s2pmd_mkwrite(new_pmd);
 
-		if (exec_fault) {
+		if (needs_exec)
 			new_pmd = kvm_s2pmd_mkexec(new_pmd);
-		} else if (fault_status == FSC_PERM) {
-			/* Preserve execute if XN was already cleared */
-			if (stage2_is_exec(kvm, fault_ipa))
-				new_pmd = kvm_s2pmd_mkexec(new_pmd);
-		}
 
 		ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
 	} else {
@@ -1621,13 +1628,8 @@  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			mark_page_dirty(kvm, gfn);
 		}
 
-		if (exec_fault) {
+		if (needs_exec)
 			new_pte = kvm_s2pte_mkexec(new_pte);
-		} else if (fault_status == FSC_PERM) {
-			/* Preserve execute if XN was already cleared */
-			if (stage2_is_exec(kvm, fault_ipa))
-				new_pte = kvm_s2pte_mkexec(new_pte);
-		}
 
 		ret = stage2_set_pte(kvm, memcache, fault_ipa, &new_pte, flags);
 	}