Re: [kvm-unit-tests PATCH v4 7/7] s390x: edat test

From: Janosch Frank <frankja@linux.ibm.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>, kvm@vger.kernel.org
Cc: linux-s390@vger.kernel.org, david@redhat.com, thuth@redhat.com,
	cohuck@redhat.com
Subject: Re: [kvm-unit-tests PATCH v4 7/7] s390x: edat test
Date: Mon, 31 May 2021 16:29:40 +0200	[thread overview]
Message-ID: <e3b80ad2-f092-ead8-9b81-d48f3f29a353@linux.ibm.com> (raw)
In-Reply-To: <20210526134245.138906-8-imbrenda@linux.ibm.com>

On 5/26/21 3:42 PM, Claudio Imbrenda wrote:
> Simple EDAT test.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Some nits below.
Acked-by Janosch Frank <frankja@linux.ibm.com>

> ---
>  s390x/Makefile      |   1 +
>  s390x/edat.c        | 274 ++++++++++++++++++++++++++++++++++++++++++++
>  s390x/unittests.cfg |   3 +
>  3 files changed, 278 insertions(+)
>  create mode 100644 s390x/edat.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index b92de9c5..26bb1684 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -21,6 +21,7 @@ tests += $(TEST_DIR)/css.elf
>  tests += $(TEST_DIR)/uv-guest.elf
>  tests += $(TEST_DIR)/sie.elf
>  tests += $(TEST_DIR)/mvpg.elf
> +tests += $(TEST_DIR)/edat.elf
>  
>  tests_binary = $(patsubst %.elf,%.bin,$(tests))
>  ifneq ($(HOST_KEY_DOCUMENT),)
> diff --git a/s390x/edat.c b/s390x/edat.c
> new file mode 100644
> index 00000000..0d56ed78
> --- /dev/null
> +++ b/s390x/edat.c
> @@ -0,0 +1,274 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * EDAT test.
> + *
> + * Copyright (c) 2021 IBM Corp
> + *
> + * Authors:
> + *	Claudio Imbrenda <imbrenda@linux.ibm.com>
> + */
> +#include <libcflat.h>
> +#include <vmalloc.h>
> +#include <asm/facility.h>
> +#include <asm/interrupt.h>
> +#include <mmu.h>
> +#include <asm/pgtable.h>
> +#include <asm-generic/barrier.h>
> +
> +#define PGD_PAGE_SHIFT (REGION1_SHIFT - PAGE_SHIFT)
> +
> +#define LC_SIZE	(2 * PAGE_SIZE)
> +#define VIRT(x)	((void *)((unsigned long)(x) + (unsigned long)mem))
> +
> +static uint8_t prefix_buf[LC_SIZE] __attribute__((aligned(LC_SIZE)));
> +static unsigned int tmp[1024] __attribute__((aligned(PAGE_SIZE)));
> +static void *root, *mem, *m;
> +static struct lowcore *lc;
> +volatile unsigned int *p;
> +
> +/*
> + * Check if a non-access-list protection exception happened for the given
> + * address, in the primary address space.
> + */
> +static bool check_pgm_prot(void *ptr)
> +{
> +	union teid teid;
> +
> +	if (lc->pgm_int_code != PGM_INT_CODE_PROTECTION)
> +		return false;
> +
> +	teid.val = lc->trans_exc_id;
> +
> +	/*
> +	 * depending on the presence of the ESOP feature, the rest of the
> +	 * field might or might not be meaningful when the m field is 0.
> +	 */
> +	if (!teid.m)
> +		return true;
> +	return (!teid.acc_list_prot && !teid.asce_id &&
> +		(teid.addr == ((unsigned long)ptr >> PAGE_SHIFT)));
> +}
> +
> +static void test_dat(void)
> +{
> +	report_prefix_push("edat off");
> +	/* disable EDAT */
> +	ctl_clear_bit(0, CTL0_EDAT);
> +
> +	/* Check some basics */
> +	p[0] = 42;
> +	report(p[0] == 42, "pte, r/w");
> +	p[0] = 0;
> +
> +	/* Write protect the page and try to write, expect a fault */
> +	protect_page(m, PAGE_ENTRY_P);
> +	expect_pgm_int();
> +	p[0] = 42;
> +	unprotect_page(m, PAGE_ENTRY_P);
> +	report(!p[0] && check_pgm_prot(m), "pte, ro");
> +
> +	/*
> +	 * The FC bit (for large pages) should be ignored because EDAT is
> +	 * off. We set a value and then we try to read it back again after
> +	 * setting the FC bit. This way we can check if large pages were
> +	 * erroneously enabled despite EDAT being off.
> +	 */
> +	p[0] = 42;
> +	protect_dat_entry(m, SEGMENT_ENTRY_FC, 4);
> +	report(p[0] == 42, "pmd, fc=1, r/w");
> +	unprotect_dat_entry(m, SEGMENT_ENTRY_FC, 4);
> +	p[0] = 0;

Could we pack that into a function and re-use it for the checks below?

> +
> +	/*
> +	 * Segment protection should work even with EDAT off, try to write
> +	 * anyway and expect a fault
> +	 */
> +	protect_dat_entry(m, SEGMENT_ENTRY_P, 4);

These page table level magic constants give me a headache.
PGTABLE_LEVEL_PMD ?

> +	expect_pgm_int();
> +	p[0] = 42;
> +	report(!p[0] && check_pgm_prot(m), "pmd, ro");
> +	unprotect_dat_entry(m, SEGMENT_ENTRY_P, 4);
> +
> +	/* The FC bit should be ignored because EDAT is off, like above */
> +	p[0] = 42;
> +	protect_dat_entry(m, REGION3_ENTRY_FC, 3);
> +	report(p[0] == 42, "pud, fc=1, r/w");
> +	unprotect_dat_entry(m, REGION3_ENTRY_FC, 3);
> +	p[0] = 0;
> +
> +	/*
> +	 * Region1/2/3 protection should not work, because EDAT is off.
> +	 * Protect the various region1/2/3 entries and write, expect the
> +	 * write to be successful.
> +	 */
> +	protect_dat_entry(m, REGION_ENTRY_P, 3);
> +	p[0] = 42;
> +	report(p[0] == 42, "pud, ro");
> +	unprotect_dat_entry(m, REGION_ENTRY_P, 3);
> +	p[0] = 0;
> +
> +	protect_dat_entry(m, REGION_ENTRY_P, 2);
> +	p[0] = 42;
> +	report(p[0] == 42, "p4d, ro");
> +	unprotect_dat_entry(m, REGION_ENTRY_P, 2);
> +	p[0] = 0;
> +
> +	protect_dat_entry(m, REGION_ENTRY_P, 1);
> +	p[0] = 42;
> +	report(p[0] == 42, "pgd, ro");
> +	unprotect_dat_entry(m, REGION_ENTRY_P, 1);
> +	p[0] = 0;
> +
> +	report_prefix_pop();
> +}
> +
> +static void test_edat1(void)
> +{
> +	report_prefix_push("edat1");
> +	/* Enable EDAT */
> +	ctl_set_bit(0, CTL0_EDAT);
> +	p[0] = 0;
> +
> +	/*
> +	 * Segment protection should work normally, try to write and expect
> +	 * a fault.
> +	 */
> +	expect_pgm_int();
> +	protect_dat_entry(m, SEGMENT_ENTRY_P, 4);
> +	p[0] = 42;
> +	report(!p[0] && check_pgm_prot(m), "pmd, ro");
> +	unprotect_dat_entry(m, SEGMENT_ENTRY_P, 4);
> +
> +	/*
> +	 * Region1/2/3 protection should work now, because EDAT is on. Try
> +	 * to write anyway and expect a fault.
> +	 */
> +	expect_pgm_int();
> +	protect_dat_entry(m, REGION_ENTRY_P, 3);
> +	p[0] = 42;
> +	report(!p[0] && check_pgm_prot(m), "pud, ro");
> +	unprotect_dat_entry(m, REGION_ENTRY_P, 3);
> +
> +	expect_pgm_int();
> +	protect_dat_entry(m, REGION_ENTRY_P, 2);
> +	p[0] = 42;
> +	report(!p[0] && check_pgm_prot(m), "p4d, ro");
> +	unprotect_dat_entry(m, REGION_ENTRY_P, 2);
> +
> +	expect_pgm_int();
> +	protect_dat_entry(m, REGION_ENTRY_P, 1);
> +	p[0] = 42;
> +	report(!p[0] && check_pgm_prot(m), "pgd, ro");
> +	unprotect_dat_entry(m, REGION_ENTRY_P, 1);
> +
> +	/* Large pages should work */
> +	p[0] = 42;
> +	install_large_page(root, 0, mem);
> +	report(p[0] == 42, "pmd, large");
> +
> +	/*
> +	 * Prefixing should not work with large pages. Since the lower
> +	 * addresses are mapped with small pages, which are subject to
> +	 * prefixing, and the pages mapped with large pages are not subject
> +	 * to prefixing, this is the resulting scenario:
> +	 *
> +	 * virtual 0 = real 0 -> absolute prefix_buf
> +	 * virtual prefix_buf = real prefix_buf -> absolute 0
> +	 * VIRT(0) -> absolute 0
> +	 * VIRT(prefix_buf) -> absolute prefix_buf
> +	 *
> +	 * The testcase checks if the memory at virtual 0 has the same
> +	 * content as the memory at VIRT(prefix_buf) and the memory at
> +	 * VIRT(0) has the same content as the memory at virtual prefix_buf.
> +	 * If prefixing is erroneously applied for large pages, the testcase
> +	 * will therefore fail.
> +	 */
> +	report(!memcmp(0, VIRT(prefix_buf), LC_SIZE) &&
> +		!memcmp(prefix_buf, VIRT(0), LC_SIZE),
> +		"pmd, large, prefixing");
> +
> +	report_prefix_pop();
> +}
> +
> +static void test_edat2(void)
> +{
> +	report_prefix_push("edat2");
> +	p[0] = 42;
> +
> +	/* Huge pages should work */
> +	install_huge_page(root, 0, mem);
> +	report(p[0] == 42, "pud, huge");
> +
> +	/* Prefixing should not work with huge pages, just like large pages */
> +	report(!memcmp(0, VIRT(prefix_buf), LC_SIZE) &&
> +		!memcmp(prefix_buf, VIRT(0), LC_SIZE),
> +		"pmd, large, prefixing");
> +
> +	report_prefix_pop();
> +}
> +
> +static unsigned int setup(void)
> +{
> +	bool has_edat1 = test_facility(8);
> +	bool has_edat2 = test_facility(78);
> +	unsigned long pa, va;
> +
> +	if (has_edat2 && !has_edat1)
> +		report_abort("EDAT2 available, but EDAT1 not available");
> +
> +	/* Setup DAT 1:1 mapping and memory management */
> +	setup_vm();
> +	root = (void *)(stctg(1) & PAGE_MASK);
> +
> +	/*
> +	 * Get a pgd worth of virtual memory, so we can test things later
> +	 * without interfering with the test code or the interrupt handler
> +	 */
> +	mem = alloc_vpages_aligned(BIT_ULL(PGD_PAGE_SHIFT), PGD_PAGE_SHIFT);
> +	assert(mem);
> +	va = (unsigned long)mem;
> +
> +	/* Map the first 1GB of real memory */
> +	for (pa = 0; pa < SZ_1G; pa += PAGE_SIZE, va += PAGE_SIZE)
> +		install_page(root, pa, (void *)va);
> +
> +	/*
> +	 * Move the lowcore to a known non-zero location. This is needed
> +	 * later to check whether prefixing is working with large pages.
> +	 */
> +	assert((unsigned long)&prefix_buf < SZ_2G);
> +	memcpy(prefix_buf, 0, LC_SIZE);
> +	set_prefix((uint32_t)(uintptr_t)prefix_buf);
> +	/* Clear the old copy */
> +	memset(prefix_buf, 0, LC_SIZE);
> +
> +	/* m will point to tmp through the new virtual mapping */
> +	m = VIRT(&tmp);
> +	/* p is the same as m but volatile */
> +	p = (volatile unsigned int *)m;
> +
> +	return has_edat1 + has_edat2;
> +}
> +
> +int main(void)
> +{
> +	unsigned int edat;
> +
> +	report_prefix_push("edat");
> +	edat = setup();
> +
> +	test_dat();
> +
> +	if (edat)
> +		test_edat1();
> +	else
> +		report_skip("EDAT not available");
> +
> +	if (edat >= 2)
> +		test_edat2();
> +	else
> +		report_skip("EDAT2 not available");
> +
> +	report_prefix_pop();
> +	return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 9f81a608..a0ec8864 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -103,3 +103,6 @@ file = sie.elf
>  [mvpg]
>  file = mvpg.elf
>  timeout = 10
> +
> +[edat]
> +file = edat.elf
> 