Re: [PATCH v3 13/21] KVM: arm64: Convert write-protect operation to generic page-table API

From: Gavin Shan <gshan@redhat.com>
To: Will Deacon <will@kernel.org>, kvmarm@lists.cs.columbia.edu
Cc: Suzuki Poulose <suzuki.poulose@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Quentin Perret <qperret@google.com>,
	James Morse <james.morse@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kernel-team@android.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 13/21] KVM: arm64: Convert write-protect operation to generic page-table API
Date: Thu, 3 Sep 2020 14:48:10 +1000	[thread overview]
Message-ID: <ab66870d-47b0-8c35-5c5c-fe25a90f37e6@redhat.com> (raw)
In-Reply-To: <20200825093953.26493-14-will@kernel.org>

Hi Will,

On 8/25/20 7:39 PM, Will Deacon wrote:
> From: Quentin Perret <qperret@google.com>
> 
> Convert stage2_wp_range() to call the kvm_pgtable_stage2_wrprotect()
> function of the generic page-table code instead of walking the page-table
> directly.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Quentin Perret <qperret@google.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>   arch/arm64/kvm/mmu.c | 25 ++++---------------------
>   1 file changed, 4 insertions(+), 21 deletions(-)
> 

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index d3db8e00ce0a..ca2c37c91e0b 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -66,6 +66,9 @@ static bool is_iomap(unsigned long flags)
>   	ret;								\
>   })
>   
> +#define stage2_apply_range_resched(kvm, addr, end, fn)			\
> +	stage2_apply_range(kvm, addr, end, fn, true)
> +
>   static bool memslot_is_logging(struct kvm_memory_slot *memslot)
>   {
>   	return memslot->dirty_bitmap && !(memslot->flags & KVM_MEM_READONLY);
> @@ -1294,27 +1297,7 @@ static void  stage2_wp_p4ds(struct kvm_s2_mmu *mmu, pgd_t *pgd,
>   static void stage2_wp_range(struct kvm_s2_mmu *mmu, phys_addr_t addr, phys_addr_t end)
>   {
>   	struct kvm *kvm = mmu->kvm;
> -	pgd_t *pgd;
> -	phys_addr_t next;
> -
> -	pgd = mmu->pgd + stage2_pgd_index(kvm, addr);
> -	do {
> -		/*
> -		 * Release kvm_mmu_lock periodically if the memory region is
> -		 * large. Otherwise, we may see kernel panics with
> -		 * CONFIG_DETECT_HUNG_TASK, CONFIG_LOCKUP_DETECTOR,
> -		 * CONFIG_LOCKDEP. Additionally, holding the lock too long
> -		 * will also starve other vCPUs. We have to also make sure
> -		 * that the page tables are not freed while we released
> -		 * the lock.
> -		 */
> -		cond_resched_lock(&kvm->mmu_lock);
> -		if (!READ_ONCE(mmu->pgd))
> -			break;
> -		next = stage2_pgd_addr_end(kvm, addr, end);
> -		if (stage2_pgd_present(kvm, *pgd))
> -			stage2_wp_p4ds(mmu, pgd, addr, next);
> -	} while (pgd++, addr = next, addr != end);
> +	stage2_apply_range_resched(kvm, addr, end, kvm_pgtable_stage2_wrprotect);
>   }
>   
>   /**
> 

Thanks,
Gavin

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