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

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Message-ID: <l3wzjxkokrcuu7mguuojr5vnzfwjpjfxgg3d6pw5zmmgsgpdfv@wz6gvpglqkiz>
Date: Fri, 19 Sep 2025 10:55:36 +0100
From: Kiryl Shutsemau <kas@...nel.org>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc: bp@...en8.de, chao.gao@...el.com, dave.hansen@...ux.intel.com, 
	isaku.yamahata@...el.com, kai.huang@...el.com, kvm@...r.kernel.org, 
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org, mingo@...hat.com, 
	pbonzini@...hat.com, seanjc@...gle.com, tglx@...utronix.de, x86@...nel.org, 
	yan.y.zhao@...el.com, vannapurve@...gle.com
Subject: Re: [PATCH v3 12/16] x86/virt/tdx: Add helpers to allow for
 pre-allocating pages

On Thu, Sep 18, 2025 at 04:22:20PM -0700, Rick Edgecombe wrote:
> In the KVM fault path pagei, tables and private pages need to be

Typo.

> 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?


-- 
  Kiryl Shutsemau / Kirill A. Shutemov