RE: [RFC PATCH V3 06/16] x86/hyperv: decrypt vmbus pages for sev-snp enlightened guest

[Michael Kelley (LINUX)]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Saturday, January 21, 2023 6:46 PM
> 

As I comment on v2 of this patch, the Subject prefix should be
"Drivers: hv: vmbus:"

> Vmbus post msg, synic event and message pages are shared

s/Vmbus/VMBus/

We're trying to be consistent about the capitalization of "VMBus"
in comments and other text. :-)

> with hypervisor and so decrypt these pages in the sev-snp guest.
> 
> Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
> ---
> Change since RFC V2:
>        * Fix error in the error code path and encrypt
>        	 pages correctly when decryption failure happens.
> ---
>  drivers/hv/hv.c | 33 ++++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 410e6c4e80d3..52edc54c8172 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -20,6 +20,7 @@
>  #include <linux/interrupt.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/mshyperv.h>
> +#include <linux/set_memory.h>
>  #include "hyperv_vmbus.h"
> 
>  /* The one and only */
> @@ -117,7 +118,7 @@ int hv_post_message(union hv_connection_id connection_id,
> 
>  int hv_synic_alloc(void)
>  {
> -	int cpu;
> +	int cpu, ret;
>  	struct hv_per_cpu_context *hv_cpu;
> 
>  	/*
> @@ -168,9 +169,39 @@ int hv_synic_alloc(void)
>  			pr_err("Unable to allocate post msg page\n");
>  			goto err;
>  		}
> +
> +		if (hv_isolation_type_en_snp()) {
> +			ret = set_memory_decrypted((unsigned long)
> +				hv_cpu->synic_message_page, 1);
> +			if (ret)
> +				goto err;
> +
> +			ret = set_memory_decrypted((unsigned long)
> +				hv_cpu->synic_event_page, 1);
> +			if (ret)
> +				goto err_decrypt_event_page;
> +
> +			ret = set_memory_decrypted((unsigned long)
> +				hv_cpu->post_msg_page, 1);
> +			if (ret)
> +				goto err_decrypt_msg_page;
> +
> +			memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
> +			memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
> +			memset(hv_cpu->post_msg_page, 0, PAGE_SIZE);
> +		}

Having decrypted the pages here in hv_synic_alloc(), shouldn't
there be corresponding re-encryption in hv_synic_free()?

>  	}
> 
>  	return 0;
> +
> +err_decrypt_msg_page:
> +	set_memory_encrypted((unsigned long)
> +		hv_cpu->synic_event_page, 1);
> +
> +err_decrypt_event_page:
> +	set_memory_encrypted((unsigned long)
> +		hv_cpu->synic_message_page, 1);
> +
>  err:
>  	/*
>  	 * Any memory allocations that succeeded will be freed when
> --
> 2.25.1