linux-kernel - Re: [PATCH] x86/mm/ptdump: display page encryption state

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Date:   Tue, 19 Apr 2022 11:57:47 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Mike Rapoport <rppt@...nel.org>, Borislav Petkov <bp@...en8.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm/ptdump: display page encryption state

On 4/19/22 07:35, Mike Rapoport wrote:
> When memory encryption is enabled, for instance in SEV guest, it is useful
> to see what memory ranges are mapped as encrypted in the kernel page tables
> and what ranges are left plain.
> 
> Add printing of 'ENC' for the encrypted ranges to the page table dumps.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
>  arch/x86/mm/dump_pagetables.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
> index e1b599ecbbc2..187dd17b8780 100644
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -201,6 +201,10 @@ static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg
>  			pt_dump_cont_printf(m, dmsg, "PCD ");
>  		else
>  			pt_dump_cont_printf(m, dmsg, "    ");
> +		if (pr & _PAGE_ENC)
> +			pt_dump_cont_printf(m, dmsg, "ENC ");
> +		else
> +			pt_dump_cont_printf(m, dmsg, "    ");

_PAGE_ENC is AMD-specific.  Could we do this with a new generic "cc_"
function, maybe cc_is_enc()?

Something like this would (I think) work for both SEV and TDX:

bool cc_is_enc(u64 prot)
{
	return cc_mkdec(prot) != prot;
}