Re: [kvm-unit-tests PATCH v3] s390x: uv-host: Add access checks for donated memory

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon, 25 Jul 2022 13:08:59 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:

> Let's check if the UV really protected all the memory we donated.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  s390x/uv-host.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/s390x/uv-host.c b/s390x/uv-host.c
> index dfcebe10..ba6c9008 100644
> --- a/s390x/uv-host.c
> +++ b/s390x/uv-host.c
> @@ -45,6 +45,32 @@ static void cpu_loop(void)
>  	for (;;) {}
>  }
>  
> +/*
> + * Checks if a memory area is protected as secure memory.
> + * Will return true if all pages are protected, false otherwise.
> + */
> +static bool access_check_3d(uint64_t *access_ptr, uint64_t len)
> +{
> +	assert(!(len & ~PAGE_MASK));
> +	assert(!((uint64_t)access_ptr & ~PAGE_MASK));
> +
> +	while (len) {
> +		expect_pgm_int();
> +		READ_ONCE(*access_ptr);
> +		if (clear_pgm_int() != PGM_INT_CODE_SECURE_STOR_ACCESS)
> +			return false;
> +		expect_pgm_int();
> +		WRITE_ONCE(*access_ptr, 42);
> +		if (clear_pgm_int() != PGM_INT_CODE_SECURE_STOR_ACCESS)
> +			return false;
> +
> +		access_ptr += PAGE_SIZE / sizeof(access_ptr);

this looks ugly, although in principle the correct way to handle a
pointer. In this specific case it's techically wrong though (you
actually want sizeof(*access_ptr) )

what about making access_ptr a char*?

then you can do just

	access_ptr += PAGE_SIZE;

and you can keep the READ_ONCE and WRITE_ONCE as they are

> +		len -= PAGE_SIZE;
> +	}
> +
> +	return true;
> +}
> +
>  static struct cmd_list cmds[] = {
>  	{ "init", UVC_CMD_INIT_UV, sizeof(struct uv_cb_init), BIT_UVC_CMD_INIT_UV },
>  	{ "create conf", UVC_CMD_CREATE_SEC_CONF, sizeof(struct uv_cb_cgc), BIT_UVC_CMD_CREATE_SEC_CONF },
> @@ -332,6 +358,10 @@ static void test_cpu_create(void)
>  	report(rc == 0 && uvcb_csc.header.rc == UVC_RC_EXECUTED &&
>  	       uvcb_csc.cpu_handle, "success");
>  
> +	rc = access_check_3d((uint64_t *)uvcb_csc.stor_origin,
> +			     uvcb_qui.cpu_stor_len);
> +	report(rc, "Storage protection");
> +
>  	tmp = uvcb_csc.stor_origin;
>  	uvcb_csc.stor_origin = (unsigned long)memalign(PAGE_SIZE, uvcb_qui.cpu_stor_len);
>  	rc = uv_call(0, (uint64_t)&uvcb_csc);
> @@ -430,6 +460,13 @@ static void test_config_create(void)
>  	rc = uv_call(0, (uint64_t)&uvcb_cgc);
>  	report(rc == 0 && uvcb_cgc.header.rc == UVC_RC_EXECUTED, "successful");
>  
> +	rc = access_check_3d((uint64_t *)uvcb_cgc.conf_var_stor_origin, vsize);
> +	report(rc, "Base storage protection");
> +
> +	rc = access_check_3d((uint64_t *)uvcb_cgc.conf_base_stor_origin,
> +			     uvcb_qui.conf_base_phys_stor_len);
> +	report(rc, "Variable storage protection");
> +
>  	uvcb_cgc.header.rc = 0;
>  	uvcb_cgc.header.rrc = 0;
>  	tmp = uvcb_cgc.guest_handle;