linux-kernel - Re: [PATCH RFC v8 19/56] x86/fault: Return pfn from dump_pagetable() for SEV-specific fault handling.

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Date:   Tue, 28 Feb 2023 18:53:50 +0800
From:   Wu Zongyong <wuzongyong@...ux.alibaba.com>
To:     Michael Roth <michael.roth@....com>
Cc:     kvm@...r.kernel.org, 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,
        rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
        bp@...en8.de, vbabka@...e.cz, kirill@...temov.name,
        ak@...ux.intel.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        dgilbert@...hat.com, jarkko@...nel.org, ashish.kalra@....com,
        nikunj.dadhania@....com, wutu.xq2@...ux.alibaba.com
Subject: Re: [PATCH RFC v8 19/56] x86/fault: Return pfn from dump_pagetable()
 for SEV-specific fault handling.

On Mon, Feb 20, 2023 at 12:38:10PM -0600, Michael Roth wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> Return pfn from dump_pagetable() to do SEV-specific
> fault handling. Used for handling SNP RMP page fault.
> 
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> Signed-off-by: Michael Roth <michael.roth@....com>
> ---
>  arch/x86/mm/fault.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index afd4cde17001..f2b16dcfbd9a 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -311,7 +311,7 @@ static bool low_pfn(unsigned long pfn)
>  	return pfn < max_low_pfn;
>  }
>  
> -static void dump_pagetable(unsigned long address)
> +static unsigned long dump_pagetable(unsigned long address)
>  {
>  	pgd_t *base = __va(read_cr3_pa());
>  	pgd_t *pgd = &base[pgd_index(address)];
> @@ -345,8 +345,10 @@ static void dump_pagetable(unsigned long address)
>  
>  	pte = pte_offset_kernel(pmd, address);
>  	pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
> +	return 0;
>  out:
>  	pr_cont("\n");
> +	return 0;
>  }
>  
>  #else /* CONFIG_X86_64: */
> @@ -367,10 +369,11 @@ static int bad_address(void *p)
>  	return get_kernel_nofault(dummy, (unsigned long *)p);
>  }
>  
> -static void dump_pagetable(unsigned long address)
> +static unsigned long dump_pagetable(unsigned long address)
>  {
>  	pgd_t *base = __va(read_cr3_pa());
>  	pgd_t *pgd = base + pgd_index(address);
> +	unsigned long pfn;

pfn should be initialized otherwise this function may return an
uninitialized value.

>  	p4d_t *p4d;
>  	pud_t *pud;
>  	pmd_t *pmd;
> @@ -388,6 +391,7 @@ static void dump_pagetable(unsigned long address)
>  	if (bad_address(p4d))
>  		goto bad;
>  
> +	pfn = p4d_pfn(*p4d);
>  	pr_cont("P4D %lx ", p4d_val(*p4d));
>  	if (!p4d_present(*p4d) || p4d_large(*p4d))
>  		goto out;
> @@ -396,6 +400,7 @@ static void dump_pagetable(unsigned long address)
>  	if (bad_address(pud))
>  		goto bad;
>  
> +	pfn = pud_pfn(*pud);
>  	pr_cont("PUD %lx ", pud_val(*pud));
>  	if (!pud_present(*pud) || pud_large(*pud))
>  		goto out;
> @@ -404,6 +409,7 @@ static void dump_pagetable(unsigned long address)
>  	if (bad_address(pmd))
>  		goto bad;
>  
> +	pfn = pmd_pfn(*pmd);
>  	pr_cont("PMD %lx ", pmd_val(*pmd));
>  	if (!pmd_present(*pmd) || pmd_large(*pmd))
>  		goto out;
> @@ -412,13 +418,14 @@ static void dump_pagetable(unsigned long address)
>  	if (bad_address(pte))
>  		goto bad;
>  
> +	pfn = pte_pfn(*pte);
>  	pr_cont("PTE %lx", pte_val(*pte));
>  out:
>  	pr_cont("\n");
> -
> -	return;
> +	return pfn;
>  bad:
>  	pr_info("BAD\n");
> +	return -1;
>  }
>  
>  #endif /* CONFIG_X86_64 */
> -- 
> 2.25.1
> 
> 
> 
>