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

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Date:   Wed, 5 Dec 2018 10:47:10 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        Punit Agrawal <punit.agrawal@....com>,
        kvmarm@...ts.cs.columbia.edu
Cc:     marc.zyngier@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>,
        punitagrawal@...il.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v9 2/8] KVM: arm/arm64: Re-factor setting the Stage 2
 entry to exec on fault



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@....com>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>> Cc: Christoffer Dall <christoffer.dall@....com>
>> Cc: Marc Zyngier <marc.zyngier@....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