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

Janosch Frank
2022-07-07T08:19:00Z

On 7/6/22 18:33, Claudio Imbrenda wrote:
> 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
>

Let me introduce you to "AGSI" add grand storage immediate.
But I get your point, inline assembly would make this much more explicit.

>> + 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;
>