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

[Janosch Frank <frankja@linux.ibm.com>]

On 7/7/22 10:11, Steffen Eiden wrote:
> Hi Janosch,
> 
> On 7/6/22 08:40, Janosch Frank 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;
>> +		if (clear_pgm_int() != PGM_INT_CODE_SECURE_STOR_ACCESS)
>> +			return false;
>> +		access_ptr += PAGE_SIZE / sizeof(access_ptr);
>> +		len -= PAGE_SIZE;
> If someone uses this function with 'len' not being a multiple of
> PAGE_SIZE this test does not for what is was intended by testing more
> memory than expected.
> 
> I suggest adding an explicit assert at the beginning of the function
> that ensures 'len' is a multiple of PAGE_SIZE.

Sure

> 
>> +	}
>> +
>> +	return true;
>> +}
>> +
> 
> [snip]
> 
> Steffen