linux-kernel - Re: [PATCH v7 10/20] x86/virt/tdx: Use all system memory when initializing TDX module as TDX memory

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Date:   Tue, 22 Nov 2022 11:10:48 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, seanjc@...gle.com, pbonzini@...hat.com,
        dave.hansen@...el.com, dan.j.williams@...el.com,
        rafael.j.wysocki@...el.com, kirill.shutemov@...ux.intel.com,
        ying.huang@...el.com, reinette.chatre@...el.com,
        len.brown@...el.com, tony.luck@...el.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, chao.gao@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, bagasdotme@...il.com,
        sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v7 10/20] x86/virt/tdx: Use all system memory when
 initializing TDX module as TDX memory

On Mon, Nov 21, 2022 at 01:26:32PM +1300, Kai Huang wrote:

> +static int build_tdx_memory(void)
> +{
> +	unsigned long start_pfn, end_pfn;
> +	int i, nid, ret;
> +
> +	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
> +		/*
> +		 * The first 1MB may not be reported as TDX convertible
> +		 * memory.  Manually exclude them as TDX memory.
> +		 *
> +		 * This is fine as the first 1MB is already reserved in
> +		 * reserve_real_mode() and won't end up to ZONE_DMA as
> +		 * free page anyway.
> +		 */
> +		start_pfn = max(start_pfn, (unsigned long)SZ_1M >> PAGE_SHIFT);
> +		if (start_pfn >= end_pfn)
> +			continue;
> +
> +		/* Verify memory is truly TDX convertible memory */
> +		if (!pfn_range_covered_by_cmr(start_pfn, end_pfn)) {
> +			pr_info("Memory region [0x%lx, 0x%lx) is not TDX convertible memorry.\n",
> +					start_pfn << PAGE_SHIFT,
> +					end_pfn << PAGE_SHIFT);
> +			return -EINVAL;

Given how tdx_cc_memory_compatible() below relies on tdx_memlist being
empty; this error patch is wrong and should goto err.

> +		}
> +
> +		/*
> +		 * Add the memory regions as TDX memory.  The regions in
> +		 * memblock has already guaranteed they are in address
> +		 * ascending order and don't overlap.
> +		 */
> +		ret = add_tdx_memblock(start_pfn, end_pfn, nid);
> +		if (ret)
> +			goto err;
> +	}
> +
> +	return 0;
> +err:
> +	free_tdx_memory();
> +	return ret;
> +}

> +bool tdx_cc_memory_compatible(unsigned long start_pfn, unsigned long end_pfn)
> +{
> +	struct tdx_memblock *tmb;
> +
> +	/* Empty list means TDX isn't enabled successfully */
> +	if (list_empty(&tdx_memlist))
> +		return true;
> +
> +	list_for_each_entry(tmb, &tdx_memlist, list) {
> +		/*
> +		 * The new range is TDX memory if it is fully covered
> +		 * by any TDX memory block.
> +		 */
> +		if (start_pfn >= tmb->start_pfn && end_pfn <= tmb->end_pfn)
> +			return true;
> +	}
> +	return false;
> +}