On Mon, 2023-03-27 at 10:21 +0200, Nico Boehr wrote:
> Since we now have the ability to run guests without MSO/MSL, add a test
> to make sure this doesn't break.
>
> Signed-off-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
> ---
> s390x/Makefile | 2 +
> s390x/sie-dat.c | 121 +++++++++++++++++++++++++++++++++++++
> s390x/snippets/c/sie-dat.c | 58 ++++++++++++++++++
> s390x/unittests.cfg | 3 +
> 4 files changed, 184 insertions(+)
> create mode 100644 s390x/sie-dat.c
> create mode 100644 s390x/snippets/c/sie-dat.c
>
Test looks good to me. Some comments below.
[...]
> diff --git a/s390x/sie-dat.c b/s390x/sie-dat.c
> new file mode 100644
> index 000000000000..37e46386181c
> --- /dev/null
> +++ b/s390x/sie-dat.c
> @@ -0,0 +1,121 @@
>
[...]
> +
> +/* keep in sync with TOTAL_PAGE_COUNT in s390x/snippets/c/sie-dat.c */
> +#define GUEST_TOTAL_PAGE_COUNT 256
This (1M) is the maximum snippet size (see snippet_setup_guest), is this intentional?
In that case the comment is inaccurate, since you'd want to sync it with the maximum snippet size.
You also know the actual snippet size SNIPPET_LEN(c, sie_dat) so I don't see why you'd need a define
at all.
> +
> +static void test_sie_dat(void)
> +{
>
[...]
> +
> + /* the guest will now write to an unmapped address and we check that this causes a segment translation */
I'd prefer "causes a segment translation exception"
[...]
> diff --git a/s390x/snippets/c/sie-dat.c b/s390x/snippets/c/sie-dat.c
> new file mode 100644
> index 000000000000..c9f7af0f3a56
> --- /dev/null
> +++ b/s390x/snippets/c/sie-dat.c
> @@ -0,0 +1,58 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Snippet used by the sie-dat.c test to verify paging without MSO/MSL
> + *
> + * Copyright (c) 2023 IBM Corp
> + *
> + * Authors:
> + * Nico Boehr <nrb@xxxxxxxxxxxxx>
> + */
> +#include <stddef.h>
> +#include <inttypes.h>
> +#include <string.h>
> +#include <asm-generic/page.h>
> +
> +/* keep in sync with GUEST_TEST_PAGE_COUNT in s390x/sie-dat.c */
> +#define TEST_PAGE_COUNT 10
> +static uint8_t test_page[TEST_PAGE_COUNT * PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
> +
> +/* keep in sync with GUEST_TOTAL_PAGE_COUNT in s390x/sie-dat.c */
> +#define TOTAL_PAGE_COUNT 256
> +
> +static inline void force_exit(void)
> +{
> + asm volatile(" diag 0,0,0x44\n");
Pretty sure the compiler will generate a leading tab, so this will be doubly indented.
> +}
> +
> +static inline void force_exit_value(uint64_t val)
> +{
> + asm volatile(
> + " diag %[val],0,0x9c\n"
> + : : [val] "d"(val)
> + );
> +}
> +
> +__attribute__((section(".text"))) int main(void)
Why is the attribute necessary? I know all the snippets have it, but I don't see
why it's necessary.
@Janosch ?
> +{
> + uint8_t *invalid_ptr;
> +
> + memset(test_page, 0, sizeof(test_page));
> + /* tell the host the page's physical address (we're running DAT off) */
> + force_exit_value((uint64_t)test_page);
> +
> + /* write some value to the page so the host can verify it */
> + for (size_t i = 0; i < TEST_PAGE_COUNT; i++)
> + test_page[i * PAGE_SIZE] = 42 + i;
> +
> + /* indicate we've written all pages */
> + force_exit();
> +
> + /* the first unmapped address */
> + invalid_ptr = (uint8_t *)(TOTAL_PAGE_COUNT * PAGE_SIZE);
Why not just use an address high enough you know it will not be mapped?
-1 should do just fine.
> + *invalid_ptr = 42;
> +
> + /* indicate we've written the non-allowed page (should never get here) */
> + force_exit();
> +
> + return 0;
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index d97eb5e943c8..aab0e670f2d4 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -215,3 +215,6 @@ file = migration-skey.elf
> smp = 2
> groups = migration
> extra_params = -append '--parallel'
> +
> +[sie-dat]
> +file = sie-dat.elf
