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 11:40:45 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "peterz@...radead.org" <peterz@...radead.org>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v7 10/20] x86/virt/tdx: Use all system memory when
 initializing TDX module as TDX memory

On Tue, 2022-11-22 at 11:10 +0100, Peter Zijlstra wrote:
> 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.

Oops.  Thanks for catching.

Also thanks for review!  Today is too late for me and I'll catch up with others
tomorrow.

> 
> > +		}
> > +
> > +		/*
> > +		 * 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;
> > +}
>