linux-kernel - Re: [PATCH v2 08/10] KVM: arm/arm64: vgic-its: free caches when GITS

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Date:   Fri, 13 Oct 2017 17:19:41 +0200
From:   Christoffer Dall <cdall@...aro.org>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, marc.zyngier@....com,
        peter.maydell@...aro.org, andre.przywara@....com,
        wanghaibin.wang@...wei.com, wu.wubin@...wei.com
Subject: Re: [PATCH v2 08/10] KVM: arm/arm64: vgic-its: free caches when
 GITS_BASER Valid bit is cleared

On Wed, Sep 27, 2017 at 03:28:38PM +0200, Eric Auger wrote:
> When the GITS_BASER<n>.Valid gets cleared, the data structures in
> guest RAM are not provisionned anymore. The device, collection

                    provisioned

		    (but did you really mean valid?)

> and LPI lists stored in the in-kernel ITS represent the same
> information in some form of cache. So let's void the cache.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  virt/kvm/arm/vgic/vgic-its.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 0df6d5f..eaefba2 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1471,8 +1471,9 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
>  				      unsigned long val)
>  {
>  	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> -	u64 entry_size, device_type;
> +	u64 entry_size;
>  	u64 reg, *regptr, clearbits = 0;
> +	int type;
>  
>  	/* When GITS_CTLR.Enable is 1, we ignore write accesses. */
>  	if (its->enabled)
> @@ -1482,12 +1483,12 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
>  	case 0:
>  		regptr = &its->baser_device_table;
>  		entry_size = abi->dte_esz;
> -		device_type = GITS_BASER_TYPE_DEVICE;
> +		type = GITS_BASER_TYPE_DEVICE;
>  		break;
>  	case 1:
>  		regptr = &its->baser_coll_table;
>  		entry_size = abi->cte_esz;
> -		device_type = GITS_BASER_TYPE_COLLECTION;
> +		type = GITS_BASER_TYPE_COLLECTION;
>  		clearbits = GITS_BASER_INDIRECT;
>  		break;
>  	default:
> @@ -1499,10 +1500,24 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
>  	reg &= ~clearbits;
>  
>  	reg |= (entry_size - 1) << GITS_BASER_ENTRY_SIZE_SHIFT;
> -	reg |= device_type << GITS_BASER_TYPE_SHIFT;
> +	reg |= (u64)type << GITS_BASER_TYPE_SHIFT;
>  	reg = vgic_sanitise_its_baser(reg);
>  
>  	*regptr = reg;
> +
> +	if (reg & GITS_BASER_VALID)
> +		return;
> +
> +	switch (type) {
> +	case GITS_BASER_TYPE_DEVICE:
> +		vgic_its_free_device_list(kvm, its);
> +		break;
> +	case GITS_BASER_TYPE_COLLECTION:
> +		vgic_its_free_collection_list(kvm, its);
> +		break;
> +	default:
> +		break;
> +	}

This block deserves a comment:
	/* Table no longer valid: clear cached data */

I would also inverse the logic and do it within an if-statement if
(!(reg & GITS_BASER_VALID)), but it's up to you.


>  }
>  
>  static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
> -- 
> 2.5.5
> 

Thanks,
-Christoffer