Re: [kvm-unit-tests PATCH v3 6/6] s390x: add a test for SIE without MSO/MSL

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

On 6/1/23 09:02, 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@linux.ibm.com>
> ---
>   s390x/Makefile             |   2 +
>   s390x/sie-dat.c            | 120 +++++++++++++++++++++++++++++++++++++
>   s390x/snippets/c/sie-dat.c |  58 ++++++++++++++++++
>   s390x/unittests.cfg        |   3 +
>   4 files changed, 183 insertions(+)
>   create mode 100644 s390x/sie-dat.c
>   create mode 100644 s390x/snippets/c/sie-dat.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index a80db538810e..4921669ee4c3 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -40,6 +40,7 @@ tests += $(TEST_DIR)/panic-loop-pgm.elf
>   tests += $(TEST_DIR)/migration-sck.elf
>   tests += $(TEST_DIR)/exittime.elf
>   tests += $(TEST_DIR)/ex.elf
> +tests += $(TEST_DIR)/sie-dat.elf
>   
>   pv-tests += $(TEST_DIR)/pv-diags.elf
>   
> @@ -120,6 +121,7 @@ snippet_lib = $(snippet_asmlib) lib/auxinfo.o
>   # perquisites (=guests) for the snippet hosts.
>   # $(TEST_DIR)/<snippet-host>.elf: snippets = $(SNIPPET_DIR)/<c/asm>/<snippet>.gbin
>   $(TEST_DIR)/mvpg-sie.elf: snippets = $(SNIPPET_DIR)/c/mvpg-snippet.gbin
> +$(TEST_DIR)/sie-dat.elf: snippets = $(SNIPPET_DIR)/c/sie-dat.gbin
>   $(TEST_DIR)/spec_ex-sie.elf: snippets = $(SNIPPET_DIR)/c/spec_ex.gbin
>   
>   $(TEST_DIR)/pv-diags.elf: pv-snippets += $(SNIPPET_DIR)/asm/snippet-pv-diag-yield.gbin
> diff --git a/s390x/sie-dat.c b/s390x/sie-dat.c
> new file mode 100644
> index 000000000000..c490a2aa825c
> --- /dev/null
> +++ b/s390x/sie-dat.c
> @@ -0,0 +1,120 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Tests SIE with paging.
> + *
> + * Copyright 2023 IBM Corp.
> + *
> + * Authors:
> + *    Nico Boehr <nrb@linux.ibm.com>
> + */
> +#include <libcflat.h>
> +#include <vmalloc.h>
> +#include <asm/asm-offsets.h>

I only did a cursory glance and wasn't able to see a use for this include.

> +#include <asm-generic/barrier.h>
> +#include <asm/pgtable.h>
> +#include <mmu.h>
> +#include <asm/page.h>
> +#include <asm/facility.h>

The sclp.h include should be enough, no?
You're not using test_facility() as far as I can see.

> +#include <asm/interrupt.h>
> +#include <asm/mem.h>
> +#include <alloc_page.h>
> +#include <sclp.h> > +#include <sie.h>
> +#include <snippet.h>
> +
> +static struct vm vm;
> +static pgd_t *guest_root;
> +
> +/* keep in sync with TEST_PAGE_COUNT in s390x/snippets/c/sie-dat.c */
> +#define GUEST_TEST_PAGE_COUNT 10
> +
> +/* keep in sync with TOTAL_PAGE_COUNT in s390x/snippets/c/sie-dat.c */
> +#define GUEST_TOTAL_PAGE_COUNT 256
> +
> +static void test_sie_dat(void)
> +{
> +	uint8_t r1;
> +	bool contents_match;
> +	uint64_t test_page_gpa, test_page_hpa;
> +	uint8_t *test_page_hva;
> +
> +	/* guest will tell us the guest physical address of the test buffer */
> +	sie(&vm);
> +
> +	r1 = (vm.sblk->ipa & 0xf0) >> 4;
> +	test_page_gpa = vm.save_area.guest.grs[r1];
> +	test_page_hpa = virt_to_pte_phys(guest_root, (void*)test_page_gpa);
> +	test_page_hva = __va(test_page_hpa);
> +	report(vm.sblk->icptcode == ICPT_INST &&
> +	       (vm.sblk->ipa & 0xFF00) == 0x8300 && vm.sblk->ipb == 0x9c0000,
> +	       "test buffer gpa=0x%lx hva=%p", test_page_gpa, test_page_hva);

You could rebase on my pv_icptdata.h patch.
Also the report string and boolean don't really relate to each other.

Not every exit needs to be a report.
Some should rather be asserts() or report_info()s.

> +
> +	/* guest will now write to the test buffer and we verify the contents */
> +	sie(&vm);
> +	report(vm.sblk->icptcode == ICPT_INST &&
> +	       vm.sblk->ipa == 0x8300 && vm.sblk->ipb == 0x440000,
> +	       "guest wrote to test buffer");

Yup pv_icptdata.h

> +
> +	contents_match = true;
> +	for (unsigned int i = 0; i < GUEST_TEST_PAGE_COUNT; i++) {
> +		uint8_t expected_val = 42 + i;

Just because you can doesn't mean that you have to.
At least leave a \n when declaring new variables...

> +		if (test_page_hva[i * PAGE_SIZE] != expected_val) {
> +			report_fail("page %u mismatch actual_val=%x expected_val=%x",
> +				    i, test_page_hva[i], expected_val);
> +			contents_match = false;
> +		}
> +	}
> +	report(contents_match, "test buffer contents match");
> +
> +	/* the guest will now write to an unmapped address and we check that this causes a segment translation exception */
> +	report_prefix_push("guest write to unmapped");
> +	expect_pgm_int();
> +	sie(&vm);
> +	check_pgm_int_code(PGM_INT_CODE_SEGMENT_TRANSLATION);
> +	report_prefix_pop();
> +}
> +

[...]

> +}
> diff --git a/s390x/snippets/c/sie-dat.c b/s390x/snippets/c/sie-dat.c
> new file mode 100644
> index 000000000000..e156d0c36c4c
> --- /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@linux.ibm.com>
> + */
> +#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");
> +}
> +
> +static inline void force_exit_value(uint64_t val)
> +{
> +	asm volatile(
> +		"diag	%[val],0,0x9c\n"
> +		: : [val] "d"(val)
> +	);
> +}

It feels like these need to go into a snippet lib.

> +
> +__attribute__((section(".text"))) int main(void)

The attribute shouldn't be needed anymore.

> +{
> +	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++)

Why is i a size_t type?

> +		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);
> +	*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 b61faf0737c3..24cd27202a08 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -218,3 +218,6 @@ extra_params = -append '--parallel'
>   
>   [execute]
>   file = ex.elf
> +
> +[sie-dat]
> +file = sie-dat.elf