linux-kernel - Re: [PATCH v4 06/16] x86/virt/tdx: Improve PAMT refcounts allocation for sparse memory

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Message-ID: <73a0ed8b993478b0854747853508f2d9b3b975db.camel@intel.com>
Date: Mon, 1 Dec 2025 22:14:41 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kas@...nel.org" <kas@...nel.org>
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Subject: Re: [PATCH v4 06/16] x86/virt/tdx: Improve PAMT refcounts allocation
 for sparse memory

On Thu, 2025-11-27 at 15:57 +0000, Kiryl Shutsemau wrote:
> > Yes, I don't see what that comment is referring to. But we do need it,
> > because hypothetically the refcount mapping could have failed halfway. So we
> > will have pte_none()s for the ranges that didn't get populated. I'll use:
> > 
> > /* Refcount mapping could have failed part way, handle aborted mappings. */
> 
> It is possible that we can have holes in physical address space between
> 0 and max_pfn. You need the check even outside of "failed halfway"
> scenario.

Err. right. Was thinking of for_each_mem_pfn_range() on the populate side.
pamt_refcount_depopulate() is just called with the whole refcount virtual
address range. I'll add both reasons to the comment.