linux-kernel - Re: [PATCH Part1 RFC v4 20/36] x86/sev: Use SEV-SNP AP creation to start secondary CPUs

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Message-ID: <YRwWSizr/xoWXivV@zn.tnic>
Date:   Tue, 17 Aug 2021 22:04:26 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part1 RFC v4 20/36] x86/sev: Use SEV-SNP AP creation to
 start secondary CPUs

On Wed, Jul 07, 2021 at 01:14:50PM -0500, Brijesh Singh wrote:
> @@ -854,6 +858,207 @@ void snp_set_memory_private(unsigned long vaddr, unsigned int npages)
>  	pvalidate_pages(vaddr, npages, 1);
>  }
>  
> +static int vmsa_rmpadjust(void *va, bool vmsa)

I know, I know it gets a bool vmsa param but you can still call it
simply rmpadjust() because this is what it does - it is a wrapper around
the insn. Just like pvalidate() and so on.

...

> +static int wakeup_cpu_via_vmgexit(int apic_id, unsigned long start_ip)
> +{
> +	struct sev_es_save_area *cur_vmsa, *vmsa;
> +	struct ghcb_state state;
> +	unsigned long flags;
> +	struct ghcb *ghcb;
> +	int cpu, err, ret;
> +	u8 sipi_vector;
> +	u64 cr4;
> +
> +	if ((sev_hv_features & GHCB_HV_FT_SNP_AP_CREATION) != GHCB_HV_FT_SNP_AP_CREATION)
> +		return -EOPNOTSUPP;
> +
> +	/*
> +	 * Verify the desired start IP against the known trampoline start IP
> +	 * to catch any future new trampolines that may be introduced that
> +	 * would require a new protected guest entry point.
> +	 */
> +	if (WARN_ONCE(start_ip != real_mode_header->trampoline_start,
> +		      "unsupported SEV-SNP start_ip: %lx\n", start_ip))

"Unsupported... " - with a capital letter

> +		return -EINVAL;
> +
> +	/* Override start_ip with known protected guest start IP */
> +	start_ip = real_mode_header->sev_es_trampoline_start;
> +

...

-- 
Regards/Gruss,
    Boris.

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