linux-kernel - Re: [RFC V1 5/5] x86: CVMs: Ensure that memory conversions happen at 2M alignment

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Date: Wed, 31 Jan 2024 08:33:07 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Vishal Annapurve <vannapurve@...gle.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Cc: pbonzini@...hat.com, rientjes@...gle.com, bgardon@...gle.com,
 seanjc@...gle.com, erdemaktas@...gle.com, ackerleytng@...gle.com,
 jxgao@...gle.com, sagis@...gle.com, oupton@...gle.com, peterx@...hat.com,
 vkuznets@...hat.com, dmatlack@...gle.com, pgonda@...gle.com,
 michael.roth@....com, kirill@...temov.name, thomas.lendacky@....com,
 dave.hansen@...ux.intel.com, linux-coco@...ts.linux.dev,
 chao.p.peng@...ux.intel.com, isaku.yamahata@...il.com,
 andrew.jones@...ux.dev, corbet@....net, hch@....de,
 m.szyprowski@...sung.com, bp@...e.de, rostedt@...dmis.org,
 iommu@...ts.linux.dev
Subject: Re: [RFC V1 5/5] x86: CVMs: Ensure that memory conversions happen at
 2M alignment

On 1/11/24 21:52, Vishal Annapurve wrote:
> @@ -2133,8 +2133,10 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
>  	int ret;
>  
>  	/* Should not be working on unaligned addresses */
> -	if (WARN_ONCE(addr & ~PAGE_MASK, "misaligned address: %#lx\n", addr))
> -		addr &= PAGE_MASK;
> +	if (WARN_ONCE(addr & ~HPAGE_MASK, "misaligned address: %#lx\n", addr)
> +		|| WARN_ONCE((numpages << PAGE_SHIFT) & ~HPAGE_MASK,
> +			"misaligned numpages: %#lx\n", numpages))
> +		return -EINVAL;

This series is talking about swiotlb and DMA, then this applies a
restriction to what I *thought* was a much more generic function:
__set_memory_enc_pgtable().  What prevents this function from getting
used on 4k mappings?