Re: [PATCH v14 00/13] SMMUv3 Nested Stage Setup (IOMMU part)

From: Sumit Gupta <sumitg@nvidia.com>
To: Marc Zyngier <maz@kernel.org>, Krishna Reddy <vdumpa@nvidia.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"vivek.gautam@arm.com" <vivek.gautam@arm.com>,
	"will@kernel.org" <will@kernel.org>,
	"eric.auger.pro@gmail.com" <eric.auger.pro@gmail.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"wangxingang5@huawei.com" <wangxingang5@huawei.com>,
	"jiangkunkun@huawei.com" <jiangkunkun@huawei.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	Vikram Sethi <vsethi@nvidia.com>, Bibek Basu <bbasu@nvidia.com>,
	"zhangfei.gao@linaro.org" <zhangfei.gao@linaro.org>,
	Shanker Donthineni <sdonthineni@nvidia.com>,
	Sachin Nikam <Snikam@nvidia.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"lushenming@huawei.com" <lushenming@huawei.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"robin.murphy@arm.com" <robin.murphy@arm.com>
Subject: Re: [PATCH v14 00/13] SMMUv3 Nested Stage Setup (IOMMU part)
Date: Sat, 24 Apr 2021 16:59:15 +0530	[thread overview]
Message-ID: <a372b4b6-ae34-c618-3569-4d5f5ab760c1@nvidia.com> (raw)
In-Reply-To: <87r1j0rqzk.wl-maz@kernel.org>

>> I have worked around the issue by filtering out the request if the
>> pfn is not valid in __clean_dcache_guest_page().  As the patch
>> wasn't posted in the community, reverted it as well.
> 
> That's papering over the real issue, and this mapping path needs
> fixing as it was only ever expected to be called for CoW.
> 
> Can you please try the following patch and let me know if that fixes
> the issue for good?
> 

Hi Marc,

Thank you for the patch. This patch fixed the crash for me.
For the formal patch, please add:

Tested-by: Sumit Gupta <sumitg@nvidia.com>

> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..b62dd40a4083 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1147,7 +1147,8 @@ int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
>           * We've moved a page around, probably through CoW, so let's treat it
>           * just like a translation fault and clean the cache to the PoC.
>           */
> -       clean_dcache_guest_page(pfn, PAGE_SIZE);
> +       if (!kvm_is_device_pfn(pfn))
> +               clean_dcache_guest_page(pfn, PAGE_SIZE);
>          handle_hva_to_gpa(kvm, hva, end, &kvm_set_spte_handler, &pfn);
>          return 0;
>   }
> 
> 
> --
> Without deviation from the norm, progress is not possible.
> 
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