Re: [kvm-unit-tests PATCH v2 1/8] s390x: uv-host: Add access checks for donated memory

Claudio Imbrenda
2022-07-06T16:33:58Z

On Wed, 6 Jul 2022 06:40:17 +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 | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/s390x/uv-host.c b/s390x/uv-host.c
> index a1a6d120..983cb4a1 100644
> --- a/s390x/uv-host.c
> +++ b/s390x/uv-host.c
> @@ -43,6 +43,24 @@ 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)
> +{
> + while (len) {
> + expect_pgm_int();
> + *access_ptr += 42;

I'm surprised this works, you will get an (expected) exception when
reading from the pointer, and then you should get another one (at this
point unexpected) when writing

> + if (clear_pgm_int() != PGM_INT_CODE_SECURE_STOR_ACCESS)
> + return false;
> + access_ptr += PAGE_SIZE / sizeof(access_ptr);
> + 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 },
> @@ -194,6 +212,10 @@ 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);
> @@ -292,6 +314,13 @@ 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;