Re: [PATCH v3 1/2] kvm: arm64: introduce new flag for non-cacheable IO memory

From: Catalin Marinas <catalin.marinas@arm.com>
To: ankita@nvidia.com
Cc: jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev,
	suzuki.poulose@arm.com, yuzenghui@huawei.com, will@kernel.org,
	alex.williamson@redhat.com, kevin.tian@intel.com,
	yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org,
	gshan@redhat.com, linux-mm@kvack.org, lpieralisi@kernel.org,
	aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com,
	targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com,
	apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com,
	mochs@nvidia.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 1/2] kvm: arm64: introduce new flag for non-cacheable IO memory
Date: Tue, 12 Dec 2023 17:31:59 +0000	[thread overview]
Message-ID: <ZXiZDwaCtHpPGXh6@arm.com> (raw)
In-Reply-To: <20231208164709.23101-2-ankita@nvidia.com>

On Fri, Dec 08, 2023 at 10:17:08PM +0530, ankita@nvidia.com wrote:
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index c651df904fe3..d4835d553c61 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -718,10 +718,17 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p
>  				kvm_pte_t *ptep)
>  {
>  	bool device = prot & KVM_PGTABLE_PROT_DEVICE;
> -	kvm_pte_t attr = device ? KVM_S2_MEMATTR(pgt, DEVICE_nGnRE) :
> -			    KVM_S2_MEMATTR(pgt, NORMAL);
> +	bool normal_nc = prot & KVM_PGTABLE_PROT_NORMAL_NC;
> +	kvm_pte_t attr;
>  	u32 sh = KVM_PTE_LEAF_ATTR_LO_S2_SH_IS;
>  
> +	if (device)
> +		attr = KVM_S2_MEMATTR(pgt, DEVICE_nGnRE);
> +	else if (normal_nc)
> +		attr = KVM_S2_MEMATTR(pgt, NORMAL_NC);
> +	else
> +		attr = KVM_S2_MEMATTR(pgt, NORMAL);

As Will said, maybe a WARN_ON_ONCE(device && normal_nc). It would fall
back to device which I think is fine.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>