linux-kernel - Re: [PATCHv2 1/3] x86/tdx: Fix early #VE handling

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Message-ID: <YofJYpBLeyNsuw5W@google.com>
Date:   Fri, 20 May 2022 17:01:22 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, linux-kernel@...r.kernel.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        thomas.lendacky@....com, x86@...nel.org
Subject: Re: [PATCHv2 1/3] x86/tdx: Fix early #VE handling

On Fri, May 20, 2022, Kirill A. Shutemov wrote:
> Move RIP in tdx_early_handle_ve() after handling the exception. Failure
> to do that leads to infinite loop of exceptions.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Fixes: 32e72854fa5f ("x86/tdx: Port I/O: Add early boot support")
> ---
>  arch/x86/coco/tdx/tdx.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 03deb4d6920d..faae53f8d559 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -447,13 +447,17 @@ static bool handle_io(struct pt_regs *regs, u32 exit_qual)
>  __init bool tdx_early_handle_ve(struct pt_regs *regs)
>  {
>  	struct ve_info ve;
> +	bool ret;
>  
>  	tdx_get_ve_info(&ve);
>  
>  	if (ve.exit_reason != EXIT_REASON_IO_INSTRUCTION)
>  		return false;
>  
> -	return handle_io(regs, ve.exit_qual);
> +	ret = handle_io(regs, ve.exit_qual);
> +	if (ret)

Ugh, the boolean returns instead of 0/-errno are fugly.  At first glance I thought
this was wrong, i.e. advancing RIP on failure.

Assuming moving away from booleans isn't happening anytime soon maybe s/ret/success
or s/ret/handled to make it more obvious that it's a happy path?