linux-kernel - Re: [PATCH RFC v9 12/51] x86/fault: Report RMP page faults for kernel addresses

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Date:   Mon, 12 Jun 2023 09:30:35 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Michael Roth <michael.roth@....com>, kvm@...r.kernel.org
Cc:     linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
        peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
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        nikunj.dadhania@....com, liam.merwick@...cle.com,
        zhi.a.wang@...el.com
Subject: Re: [PATCH RFC v9 12/51] x86/fault: Report RMP page faults for kernel
 addresses

On 6/11/23 21:25, Michael Roth wrote:
>  	dump_pagetable(address);
> +
> +	if (error_code & X86_PF_RMP) {
> +		unsigned int level;
> +		pgd_t *pgd;
> +		pte_t *pte;
> +
> +		pgd = __va(read_cr3_pa());
> +		pgd += pgd_index(address);
> +		pte = lookup_address_in_pgd(pgd, address, &level);
> +
> +		sev_dump_rmpentry(pte_pfn(*pte));
> +	}
>  }

It would be nice to trim this hunk down.  Can you make it:

	if (error_code & X86_PF_RMP)
		sev_dump_rmpentry(address);

and hide the rest of the logic in the helper?

Oh, and lookup_address_in_pgd() can return NULL.  It's not great to page
fault in the page fault handler.  Could you fix that up too, please?