linux-kernel - Re: [PATCH 1/2] irqchip/gic-v3-its: Share ITS tables with a non-trusted hypervisor

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Message-ID: <ZtsvhESaBDdyEs7B@arm.com>
Date: Fri, 6 Sep 2024 17:36:20 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Steven Price <steven.price@....com>
Cc: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Will Deacon <will@...nel.org>,
	Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH 1/2] irqchip/gic-v3-its: Share ITS tables with a
 non-trusted hypervisor

On Thu, Sep 05, 2024 at 10:17:37AM +0100, Steven Price wrote:
> +static struct page *its_alloc_pages_node(int node, gfp_t gfp,
> +					 unsigned int order)
> +{
> +	struct page *page;
> +	int ret = 0;
> +
> +	page = alloc_pages_node(node, gfp, order);
> +
> +	if (!page)
> +		return NULL;
> +
> +	ret = set_memory_decrypted((unsigned long)page_address(page),
> +				   1 << order);
> +	if (WARN_ON(ret))
> +		return NULL;

I think we discussed this but forgot the details. If
set_memory_decrypted() failed, I guess it's not safe to free the page
back as we don't know the state it is in. It might be worth adding a
comment if you respin for other reasons.

> +static void *itt_alloc_pool(int node, int size)
> +{
> +	unsigned long addr;
> +	struct page *page;
> +
> +	if (size >= PAGE_SIZE) {
> +		page = its_alloc_pages_node(node,
> +					    GFP_KERNEL | __GFP_ZERO,
> +					    get_order(size));
> +
> +		return page_address(page);
> +	}

Since its_alloc_pages_node() can return NULL, we should check for this
as page_address() would not be valid.

Otherwise the patch looks fine:

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