linux-kernel - Re: [PATCH V8 5/9] x86/sev-es: Expose sev_es_ghcb_hv_call() to call ghcb hv call out of sev code

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Message-ID: <YXGTwppQ8syUyJ72@zn.tnic>
Date:   Thu, 21 Oct 2021 18:22:26 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        davem@...emloft.net, kuba@...nel.org, gregkh@...uxfoundation.org,
        arnd@...db.de, brijesh.singh@....com, jroedel@...e.de,
        Tianyu.Lan@...rosoft.com, thomas.lendacky@....com,
        rientjes@...gle.com, pgonda@...gle.com, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, rppt@...nel.org,
        saravanand@...com, aneesh.kumar@...ux.ibm.com, hannes@...xchg.org,
        tj@...nel.org, michael.h.kelley@...rosoft.com,
        linux-arch@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        vkuznets@...hat.com, konrad.wilk@...cle.com, hch@....de,
        robin.murphy@....com, joro@...tes.org, parri.andrea@...il.com,
        dave.hansen@...el.com
Subject: Re: [PATCH V8 5/9] x86/sev-es: Expose sev_es_ghcb_hv_call() to call
 ghcb hv call out of sev code

On Thu, Oct 21, 2021 at 11:41:05AM -0400, Tianyu Lan wrote:
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index ea9abd69237e..368ed36971e3 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -124,10 +124,9 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt
>  	return ES_VMM_ERROR;
>  }
>  
> -static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
> -					  struct es_em_ctxt *ctxt,
> -					  u64 exit_code, u64 exit_info_1,
> -					  u64 exit_info_2)
> +enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, bool set_ghcb_msr,
> +				   struct es_em_ctxt *ctxt, u64 exit_code,
> +				   u64 exit_info_1, u64 exit_info_2)
>  {
>  	/* Fill in protocol and format specifiers */
>  	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
> @@ -137,7 +136,15 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
>  	ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
>  	ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
>  
> -	sev_es_wr_ghcb_msr(__pa(ghcb));
> +	/*
> +	 * Hyper-V unenlightened guests use a paravisor for communicating and
> +	 * GHCB pages are being allocated and set up by that paravisor. Linux
> +	 * should not change ghcb page pa in such case and so add set_ghcb_msr

"... not change the GHCB page's physical address."

Remove the "so add... " rest.

Otherwise, LGTM.

Do you want me to take it through the tip tree?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette