linux-kernel - Re: [PATCH v2 1/5] selftests/sgx: Retry the ioctl()'s returned with EAGAIN

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Date:   Thu, 8 Sep 2022 15:43:06 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>, <linux-sgx@...r.kernel.org>
CC:     Haitao Huang <haitao.huang@...ux.intel.com>,
        Vijay Dhanraj <vijay.dhanraj@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Shuah Khan" <shuah@...nel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] selftests/sgx: Retry the ioctl()'s returned with
 EAGAIN

Hi Jarkko and Haitao,

On 9/4/2022 7:04 PM, Jarkko Sakkinen wrote:
> From: Haitao Huang <haitao.huang@...ux.intel.com>
> 
> For EMODT and EREMOVE ioctl()'s with a large range, kernel
> may not finish in one shot and return EAGAIN error code
> and count of bytes of EPC pages on that operations are
> finished successfully.
> 
> Change the unclobbered_vdso_oversubscribed_remove test
> to rerun the ioctl()'s in a loop, updating offset and length
> using the byte count returned in each iteration.
> 
> Fixes: 6507cce561b4 ("selftests/sgx: Page removal stress test")

Should this patch be moved to the "critical fixes for v6.0" series?

> Signed-off-by: Haitao Huang <haitao.huang@...ux.intel.com>
> Tested-by: Jarkko Sakkinen <jarkko@...nel.org>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
> v3:
> * Added a fixes tag. The bug is in v6.0 patches.
> * Added my tested-by (the bug reproduced in my NUC often).
> v2:
> * Changed branching in EAGAIN condition so that else branch
>   is not required.
> * Addressed Reinette's feedback:
> ---
>  tools/testing/selftests/sgx/main.c | 42 ++++++++++++++++++++++++------
>  1 file changed, 34 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c
> index 9820b3809c69..59cca806eda1 100644
> --- a/tools/testing/selftests/sgx/main.c
> +++ b/tools/testing/selftests/sgx/main.c
> @@ -390,6 +390,7 @@ TEST_F_TIMEOUT(enclave, unclobbered_vdso_oversubscribed_remove, 900)
>  	struct encl_segment *heap;
>  	unsigned long total_mem;
>  	int ret, errno_save;
> +	unsigned long count;
>  	unsigned long addr;
>  	unsigned long i;
>  
> @@ -453,16 +454,30 @@ TEST_F_TIMEOUT(enclave, unclobbered_vdso_oversubscribed_remove, 900)
>  	modt_ioc.offset = heap->offset;
>  	modt_ioc.length = heap->size;
>  	modt_ioc.page_type = SGX_PAGE_TYPE_TRIM;
> -
> +	count = 0;
>  	TH_LOG("Changing type of %zd bytes to trimmed may take a while ...",
>  	       heap->size);
> -	ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &modt_ioc);
> -	errno_save = ret == -1 ? errno : 0;
> +	do {
> +		ret = ioctl(self->encl.fd, SGX_IOC_ENCLAVE_MODIFY_TYPES, &modt_ioc);
> +
> +		errno_save = ret == -1 ? errno : 0;
> +		if (errno_save != EAGAIN)
> +			break;
> +
> +		EXPECT_EQ(modt_ioc.result, 0);

If this check triggers then there is something seriously wrong and in that case
it may also be that this loop may be unable to terminate or the error condition would
keep appearing until the loop terminates (which may be many iterations). Considering
the severity and risk I do think that ASSERT_EQ() would be more appropriate,
similar to how ASSERT_EQ() is used in patch 5/5.

Apart from that I think that this looks good.

Thank you very much for adding this.

Reinette