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

[Michael Kelley (LINUX)]

From: Tianyu Lan <ltykernel@xxxxxxxxx> 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@xxxxxxxxxxxxx>
> ---
>  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@xxxxxxxxxxxxx>