linux-kernel - Re: [PATCH v3 12/16] x86/virt/tdx: Add helpers to allow for pre-allocating pages

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Message-ID: <5ed71682f0ed725c69d4900cfb1ee15cd6f791b3.camel@intel.com>
Date: Wed, 1 Oct 2025 19:48:51 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kas@...nel.org" <kas@...nel.org>
CC: "Gao, Chao" <chao.gao@...el.com>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"Huang, Kai" <kai.huang@...el.com>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"bp@...en8.de" <bp@...en8.de>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "mingo@...hat.com" <mingo@...hat.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v3 12/16] x86/virt/tdx: Add helpers to allow for
 pre-allocating pages

On Fri, 2025-09-19 at 10:55 +0100, Kiryl Shutsemau wrote:
> > installed under a spin lock. This means that the operations around
> > installing PAMT pages for them will not be able to allocate pages.
> > 
> 
> > +static inline struct page *get_tdx_prealloc_page(struct tdx_prealloc
> > *prealloc)
> > +{
> > +	struct page *page;
> > +
> > +	page = list_first_entry_or_null(&prealloc->page_list, struct page,
> > lru);
> > +	if (page) {
> > +		list_del(&page->lru);
> > +		prealloc->cnt--;
> > +	}
> > +
> 
> For prealloc->cnt == 0, kvm_mmu_memory_cache_alloc() does allocation
> with GFP_ATOMIC after WARN().
> 
> Do we want the same here?

Uhh, hmm. I'd hope to keep it as simple as possible, but I suppose that this is
a regression from the current upstream level of safety. I'll add it.