linux-kernel - Re: [PATCH 2/6] x86/sgx: Handle VA page allocation failure for EAUG on PF.

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Message-ID: <7be76cf8-28c4-edcf-aa67-703b5c18bef1@intel.com>
Date:   Tue, 30 Aug 2022 15:54:54 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>, <linux-sgx@...r.kernel.org>
CC:     Haitao Huang <haitao.huang@...ux.intel.com>,
        Vijay Dhanraj <vijay.dhanraj@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "Borislav Petkov" <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] x86/sgx: Handle VA page allocation failure for EAUG
 on PF.

Hi Jarkko and Haitao,

On 8/29/2022 8:12 PM, Jarkko Sakkinen wrote:
> From: Haitao Huang <haitao.huang@...ux.intel.com>
> 
> VM_FAULT_NOPAGE is expected behaviour for -EBUSY failure path, when
> augmenting a page, as this means that the reclaimer thread has been
> triggered, and the intention is just to round-trip in ring-3, and
> retry with a new page fault.

Thank you very much for finding and fixing this issue.

> 
> Fixes: 5a90d2c3f5ef ("x86/sgx: Support adding of pages to an initialized enclave")
> Signed-off-by: Haitao Huang <haitao.huang@...ux.intel.com>
> Tested-by: Vijay Dhanraj <vijay.dhanraj@...el.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
> v2:
> * Removed reviewed-by, no other changes.
> ---
>  arch/x86/kernel/cpu/sgx/encl.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index 24c1bb8eb196..de92c1c8b79d 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -344,8 +344,11 @@ static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
>  	}
>  
>  	va_page = sgx_encl_grow(encl, false);
> -	if (IS_ERR(va_page))
> +	if (IS_ERR(va_page)) {
> +		if (PTR_ERR(va_page) == -EBUSY)
> +			vmret =  VM_FAULT_NOPAGE;

Some unnecessary white space remained after the copy of this snippet. No
need to propagate that mistake.

>  		goto err_out_epc;
> +	}
>  
>  	if (va_page)
>  		list_add(&va_page->list, &encl->va_pages);


Apart from the white space nitpick this looks good.

Thank you very much.

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette