linux-kernel - Re: [PATCH v8 06/11] x86/traps: Add #VE support for TDX guest

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Message-ID: <YV8pE+QYcS/fUe98@zn.tnic>
Date:   Thu, 7 Oct 2021 19:06:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 06/11] x86/traps: Add #VE support for TDX guest

On Mon, Oct 04, 2021 at 07:52:00PM -0700, Kuppuswamy Sathyanarayanan wrote:
> diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
> index d5fc2904facf..f7885c777a09 100644
> --- a/arch/x86/kernel/tdx.c
> +++ b/arch/x86/kernel/tdx.c
> @@ -6,6 +6,9 @@
>  
>  #include <asm/tdx.h>
>  
> +/* TDX Module call Leaf IDs */
> +#define TDGETVEINFO			3
> +
>  /*
>   * Allocate it in the data region to avoid zeroing it during
>   * BSS initialization. It is mainly used in cc_platform_has()
> @@ -50,6 +53,36 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14,
>  	return out->r10;
>  }
>  
> +unsigned long tdx_get_ve_info(struct ve_info *ve)
> +{
> +	struct tdx_module_output out = {0};
> +	u64 ret;
> +
> +	/*
> +	 * NMIs and machine checks are suppressed. Before this point any
> +	 * #VE is fatal. After this point (TDGETVEINFO call), NMIs and
> +	 * additional #VEs are permitted (but it is expected not to
> +	 * happen unless kernel panics).
> +	 */
> +	ret = __tdx_module_call(TDGETVEINFO, 0, 0, 0, 0, &out);

Same question as before - why do you need to clear this @out thing above
when __tdx_module_call() will overwrite it?

What you should do instead is check that @ve pointer which you get
passed in - it might be NULL.

> +	ve->exit_reason = out.rcx;
> +	ve->exit_qual   = out.rdx;
> +	ve->gla         = out.r8;
> +	ve->gpa         = out.r9;
> +	ve->instr_len   = out.r10 & UINT_MAX;
> +	ve->instr_info  = out.r10 >> 32;
> +
> +	return ret;
> 
-- 
Regards/Gruss,
    Boris.

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