linux-kernel - Re: [RFC PATCH v2 12/58] KVM: arm64: Add __pkvm_{use, unuse}

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Message-ID: <Z2QCGFN5V41Vux6Z@google.com>
Date: Thu, 19 Dec 2024 11:23:04 +0000
From: Quentin Perret <qperret@...gle.com>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: iommu@...ts.linux.dev, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	catalin.marinas@....com, will@...nel.org, maz@...nel.org,
	oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, robdclark@...il.com, joro@...tes.org,
	robin.murphy@....com, jean-philippe@...aro.org, jgg@...pe.ca,
	nicolinc@...dia.com, vdonnefort@...gle.com, tabba@...gle.com,
	danielmentz@...gle.com, tzukui@...gle.com
Subject: Re: [RFC PATCH v2 12/58] KVM: arm64: Add __pkvm_{use, unuse}_dma()

On Thursday 12 Dec 2024 at 18:03:36 (+0000), Mostafa Saleh wrote:
> +int __pkvm_host_unuse_dma(phys_addr_t phys_addr, size_t size)
> +{
> +	int i;
> +	size_t nr_pages = size >> PAGE_SHIFT;
> +
> +	if (WARN_ON(!PAGE_ALIGNED(phys_addr | size)))
> +		return -EINVAL;
> +
> +	host_lock_component();
> +	if (!range_is_memory(phys_addr, phys_addr + size))
> +		goto out_ret;

Nit: I think you can do this out of the critical section -- the memblock
list is guaranteed stable by construction.

> +	/*
> +	 * We end up here after the caller successfully unmapped the page from
> +	 * the IOMMU table. Which means that a ref is held, the page is shared
> +	 * in the host s2, there can be no failure.
> +	 */
> +	for (i = 0; i < nr_pages; i++)
> +		__pkvm_host_unuse_dma_page(phys_addr + i * PAGE_SIZE);
> +
> +out_ret:
> +	host_unlock_component();
> +	return 0;
> +}
> +
>  int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu,
>  			    enum kvm_pgtable_prot prot)
>  {
> -- 
> 2.47.0.338.g60cca15819-goog
>