linux-kernel - Re: [PATCH 62/70] x86/kvm: Add KVM specific VMMCALL handling under SEV-ES

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Date:   Fri, 20 Mar 2020 14:23:58 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com
cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 62/70] x86/kvm: Add KVM specific VMMCALL handling under
 SEV-ES

On Thu, 19 Mar 2020, Joerg Roedel wrote:

> From: Tom Lendacky <thomas.lendacky@....com>
> 
> Implement the callbacks to copy the processor state required by KVM to
> the GHCB.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> [ jroedel@...e.de: - Split out of a larger patch
>                    - Adapt to different callback functions ]
> Co-developed-by: Joerg Roedel <jroedel@...e.de>
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  arch/x86/kernel/kvm.c | 35 +++++++++++++++++++++++++++++------
>  1 file changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 6efe0410fb72..0e3fc798d719 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -34,6 +34,8 @@
>  #include <asm/hypervisor.h>
>  #include <asm/tlb.h>
>  #include <asm/cpuidle_haltpoll.h>
> +#include <asm/ptrace.h>
> +#include <asm/svm.h>
>  
>  static int kvmapf = 1;
>  
> @@ -729,13 +731,34 @@ static void __init kvm_init_platform(void)
>  	x86_platform.apic_post_init = kvm_apic_init;
>  }
>  
> +#if defined(CONFIG_AMD_MEM_ENCRYPT)
> +static void kvm_sev_es_hcall_prepare(struct ghcb *ghcb, struct pt_regs *regs)
> +{
> +	/* RAX and CPL are already in the GHCB */
> +	ghcb_set_rbx(ghcb, regs->bx);
> +	ghcb_set_rcx(ghcb, regs->cx);
> +	ghcb_set_rdx(ghcb, regs->dx);
> +	ghcb_set_rsi(ghcb, regs->si);

Is it possible to check the hypercall from RAX and only copy the needed 
regs or is there a requirement that they must all be copied 
unconditionally?

> +}
> +
> +static bool kvm_sev_es_hcall_finish(struct ghcb *ghcb, struct pt_regs *regs)
> +{
> +	/* No checking of the return state needed */
> +	return true;
> +}
> +#endif
> +
>  const __initconst struct hypervisor_x86 x86_hyper_kvm = {
> -	.name			= "KVM",
> -	.detect			= kvm_detect,
> -	.type			= X86_HYPER_KVM,
> -	.init.guest_late_init	= kvm_guest_init,
> -	.init.x2apic_available	= kvm_para_available,
> -	.init.init_platform	= kvm_init_platform,
> +	.name				= "KVM",
> +	.detect				= kvm_detect,
> +	.type				= X86_HYPER_KVM,
> +	.init.guest_late_init		= kvm_guest_init,
> +	.init.x2apic_available		= kvm_para_available,
> +	.init.init_platform		= kvm_init_platform,
> +#if defined(CONFIG_AMD_MEM_ENCRYPT)
> +	.runtime.sev_es_hcall_prepare	= kvm_sev_es_hcall_prepare,
> +	.runtime.sev_es_hcall_finish	= kvm_sev_es_hcall_finish,
> +#endif
>  };
>  
>  static __init int activate_jump_labels(void)
> -- 
> 2.17.1
> 
>