linux-kernel - Re: [PATCH v2 2/4] KVM: arm/arm64: Introduce helpers to manupulate page table entries

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Date:   Tue, 1 May 2018 11:36:26 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Punit Agrawal <punit.agrawal@....com>, kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, marc.zyngier@....com,
        christoffer.dall@....com, linux-kernel@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v2 2/4] KVM: arm/arm64: Introduce helpers to manupulate
 page table entries

On 01/05/18 11:26, Punit Agrawal wrote:
> Introduce helpers to abstract architectural handling of the conversion
> of pfn to page table entries and marking a PMD page table entry as a
> block entry.
> 
> The helpers are introduced in preparation for supporting PUD hugepages
> at stage 2 - which are supported on arm64 but do not exist on arm.

Punit,

The change are fine by me. However, we usually do not define kvm_*
accessors for something which we know matches with the host variant.
i.e, PMD and PTE helpers, which are always present and we make use
of them directly. (see unmap_stage2_pmds for e.g)

Cheers
Suzuki

> 
> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
> Acked-by: Christoffer Dall <christoffer.dall@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> ---
>   arch/arm/include/asm/kvm_mmu.h   | 5 +++++
>   arch/arm64/include/asm/kvm_mmu.h | 5 +++++
>   virt/kvm/arm/mmu.c               | 7 ++++---
>   3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
> index 707a1f06dc5d..5907a81ad5c1 100644
> --- a/arch/arm/include/asm/kvm_mmu.h
> +++ b/arch/arm/include/asm/kvm_mmu.h
> @@ -75,6 +75,11 @@ phys_addr_t kvm_get_idmap_vector(void);
>   int kvm_mmu_init(void);
>   void kvm_clear_hyp_idmap(void);
>   
> +#define kvm_pfn_pte(pfn, prot)	pfn_pte(pfn, prot)
> +#define kvm_pfn_pmd(pfn, prot)	pfn_pmd(pfn, prot)
> +
> +#define kvm_pmd_mkhuge(pmd)	pmd_mkhuge(pmd)
> +
>   static inline void kvm_set_pmd(pmd_t *pmd, pmd_t new_pmd)
>   {
>   	*pmd = new_pmd;
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 082110993647..d962508ce4b3 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -173,6 +173,11 @@ void kvm_clear_hyp_idmap(void);
>   #define	kvm_set_pte(ptep, pte)		set_pte(ptep, pte)
>   #define	kvm_set_pmd(pmdp, pmd)		set_pmd(pmdp, pmd)
>   
> +#define kvm_pfn_pte(pfn, prot)		pfn_pte(pfn, prot)
> +#define kvm_pfn_pmd(pfn, prot)		pfn_pmd(pfn, prot)
> +
> +#define kvm_pmd_mkhuge(pmd)		pmd_mkhuge(pmd)
> +
>   static inline pte_t kvm_s2pte_mkwrite(pte_t pte)
>   {
>   	pte_val(pte) |= PTE_S2_RDWR;
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index 686fc6a4b866..74750236f445 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1554,8 +1554,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>   		invalidate_icache_guest_page(pfn, vma_pagesize);
>   
>   	if (hugetlb) {
> -		pmd_t new_pmd = pfn_pmd(pfn, mem_type);
> -		new_pmd = pmd_mkhuge(new_pmd);
> +		pmd_t new_pmd = kvm_pfn_pmd(pfn, mem_type);
> +
> +		new_pmd = kvm_pmd_mkhuge(new_pmd);
>   		if (writable)
>   			new_pmd = kvm_s2pmd_mkwrite(new_pmd);
>   
> @@ -1564,7 +1565,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>   
>   		ret = stage2_set_pmd_huge(kvm, memcache, fault_ipa, &new_pmd);
>   	} else {
> -		pte_t new_pte = pfn_pte(pfn, mem_type);
> +		pte_t new_pte = kvm_pfn_pte(pfn, mem_type);
>   
>   		if (writable) {
>   			new_pte = kvm_s2pte_mkwrite(new_pte);
>