linux-kernel - RE: [PATCH V2 3/9] x86/hyperv: Mark Hyper-V vp assist page unencrypted in SEV-SNP enlightened guest

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Message-ID: <BYAPR21MB1688D1207B957D63839EF398D72EA@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Tue, 4 Jul 2023 14:18:45 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Tianyu Lan <ltykernel@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "arnd@...db.de" <arnd@...db.de>
CC:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: RE: [PATCH V2 3/9] x86/hyperv: Mark Hyper-V vp assist page
 unencrypted in SEV-SNP enlightened guest

From: Tianyu Lan <ltykernel@...il.com> Sent: Monday, June 26, 2023 8:23 PM
> 
> hv vp assist page needs to be shared between SEV-SNP guest and Hyper-V.
> So mark the page unencrypted in the SEV-SNP guest.
> 
> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> ---
>  arch/x86/hyperv/hv_init.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 1ba367a9686e..b004370d3b01 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -18,6 +18,7 @@
>  #include <asm/hyperv-tlfs.h>
>  #include <asm/mshyperv.h>
>  #include <asm/idtentry.h>
> +#include <asm/set_memory.h>
>  #include <linux/kexec.h>
>  #include <linux/version.h>
>  #include <linux/vmalloc.h>
> @@ -106,8 +107,21 @@ static int hv_cpu_init(unsigned int cpu)
>  		 * in hv_cpu_die(), otherwise a CPU may not be stopped in the
>  		 * case of CPU offlining and the VM will hang.
>  		 */
> -		if (!*hvp)
> +		if (!*hvp) {
>  			*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
> +
> +			/*
> +			 * Hyper-V should never specify a VM that is a Confidential
> +			 * VM and also running in the root partition. Root partition
> +			 * is blocked to run in Confidential VM. So only decrypt assist
> +			 * page in non-root partition here.
> +			 */
> +			if (*hvp && hv_isolation_type_en_snp()) {
> +				WARN_ON_ONCE(set_memory_decrypted((unsigned
> long)(*hvp), 1));
> +				memset(*hvp, 0, PAGE_SIZE);
> +			}
> +		}
> +
>  		if (*hvp)
>  			msr.pfn = vmalloc_to_pfn(*hvp);
> 
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>