On Thu, 10 Oct 2024 09:11:52 +0200
Nico Boehr <nrb@xxxxxxxxxxxxx> wrote:
> This adds a test for diag258 (page ref service/async page fault).
>
> There recently was a virtual-real address confusion bug, so we should
> test:
> - diag258 parameter Rx is a real adress
> - crossing the end of RAM with the parameter list yields an addressing
> exception
> - invalid diagcode in the parameter block yields an specification
> exception
> - diag258 correctly applies prefixing.
>
> Note that we're just testing error cases as of now.
>
> Signed-off-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> s390x/Makefile | 1 +
> s390x/diag258.c | 259 ++++++++++++++++++++++++++++++++++++++++++++
> s390x/unittests.cfg | 3 +
> 3 files changed, 263 insertions(+)
> create mode 100644 s390x/diag258.c
>
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 23342bd64f44..66d71351caab 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -44,6 +44,7 @@ tests += $(TEST_DIR)/exittime.elf
> tests += $(TEST_DIR)/ex.elf
> tests += $(TEST_DIR)/topology.elf
> tests += $(TEST_DIR)/sie-dat.elf
> +tests += $(TEST_DIR)/diag258.elf
>
> pv-tests += $(TEST_DIR)/pv-diags.elf
> pv-tests += $(TEST_DIR)/pv-icptcode.elf
> diff --git a/s390x/diag258.c b/s390x/diag258.c
> new file mode 100644
> index 000000000000..4746615bb944
> --- /dev/null
> +++ b/s390x/diag258.c
> @@ -0,0 +1,259 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Diag 258: Async Page Fault Handler
> + *
> + * Copyright (c) 2024 IBM Corp
> + *
> + * Authors:
> + * Nico Boehr <nrb@xxxxxxxxxxxxx>
> + */
> +
> +#include <libcflat.h>
> +#include <asm-generic/barrier.h>
> +#include <asm/asm-offsets.h>
> +#include <asm/interrupt.h>
> +#include <asm/mem.h>
> +#include <asm/pgtable.h>
> +#include <mmu.h>
> +#include <sclp.h>
> +#include <vmalloc.h>
> +
> +static uint8_t prefix_buf[LC_SIZE] __attribute__((aligned(LC_SIZE)));
> +
> +#define __PF_RES_FIELD 0x8000000000000000UL
> +
> +/* copied from Linux arch/s390/mm/pfault.c */
> +struct pfault_refbk {
> + u16 refdiagc;
> + u16 reffcode;
> + u16 refdwlen;
> + u16 refversn;
> + u64 refgaddr;
> + u64 refselmk;
> + u64 refcmpmk;
> + u64 reserved;
> +};
> +
> +uint64_t pfault_token = 0x0123fadec0fe3210UL;
> +
> +static struct pfault_refbk pfault_init_refbk __attribute__((aligned(8))) = {
> + .refdiagc = 0x258,
> + .reffcode = 0, /* TOKEN */
> + .refdwlen = sizeof(struct pfault_refbk) / sizeof(uint64_t),
> + .refversn = 2,
> + .refgaddr = (u64)&pfault_token,
> + .refselmk = 1UL << 48,
> + .refcmpmk = 1UL << 48,
> + .reserved = __PF_RES_FIELD
> +};
> +
> +static struct pfault_refbk pfault_cancel_refbk __attribute((aligned(8))) = {
> + .refdiagc = 0x258,
> + .reffcode = 1, /* CANCEL */
> + .refdwlen = sizeof(struct pfault_refbk) / sizeof(uint64_t),
> + .refversn = 2,
> + .refgaddr = 0,
> + .refselmk = 0,
> + .refcmpmk = 0,
> + .reserved = 0
> +};
> +
> +static inline int diag258(struct pfault_refbk *refbk)
> +{
> + int rc = -1;
> +
> + asm volatile(
> + " diag %[refbk],%[rc],0x258\n"
> + : [rc] "+d" (rc)
> + : [refbk] "a" (refbk), "m" (*(refbk))
> + : "cc");
> + return rc;
> +}
> +
> +static void test_priv(void)
> +{
> + report_prefix_push("privileged");
> + expect_pgm_int();
> + enter_pstate();
> + diag258(&pfault_init_refbk);
> + check_pgm_int_code(PGM_INT_CODE_PRIVILEGED_OPERATION);
> + report_prefix_pop();
> +}
> +
> +static void* page_map_outside_real_space(phys_addr_t page_real)
> +{
> + pgd_t *root = (pgd_t *)(stctg(1) & PAGE_MASK);
> + void* vaddr = alloc_vpage();
> +
> + install_page(root, page_real, vaddr);
> +
> + return vaddr;
> +}
> +
> +/*
> + * Verify that the refbk pointer is a real address and not a virtual
> + * address. This is tested by enabling DAT and establishing a mapping
> + * for the refbk that is outside of the bounds of our (guest-)physical
> + * address space.
> + */
> +static void test_refbk_real(void)
> +{
> + struct pfault_refbk *refbk;
> + void *refbk_page;
> + pgd_t *root;
> +
> + report_prefix_push("refbk is real");
> +
> + /* Set up virtual memory and allocate a physical page for storing the refbk */
> + setup_vm();
> + refbk_page = alloc_page();
> +
> + /* Map refblk page outside of physical memory identity mapping */
> + root = (pgd_t *)(stctg(1) & PAGE_MASK);
> + refbk = page_map_outside_real_space(virt_to_pte_phys(root, refbk_page));
> +
> + /* Assert the mapping really is outside identity mapping */
> + report_info("refbk is at 0x%lx", (u64)refbk);
> + report_info("ram size is 0x%lx", get_ram_size());
> + assert((u64)refbk > get_ram_size());
> +
> + /* Copy the init refbk to the page */
> + memcpy(refbk, &pfault_init_refbk, sizeof(struct pfault_refbk));
> +
> + /* Protect the virtual mapping to avoid diag258 actually doing something */
> + protect_page(refbk, PAGE_ENTRY_I);
> +
> + expect_pgm_int();
> + diag258(refbk);
> + check_pgm_int_code(PGM_INT_CODE_ADDRESSING);
> + report_prefix_pop();
> +
> + free_page(refbk_page);
> + disable_dat();
> + irq_set_dat_mode(false, 0);
> +}
> +
> +/*
> + * Verify diag258 correctly applies prefixing.
> + */
> +static void test_refbk_prefixing(void)
> +{
> + const size_t lowcore_offset_for_refbk = offsetof(struct lowcore, pad_0x03a0);
> + struct pfault_refbk *refbk_in_prefix, *refbk_in_reverse_prefix;
> + uint32_t old_prefix;
> + uint64_t ry;
> +
> + report_prefix_push("refbk prefixing");
> +
> + report_info("refbk at lowcore offset 0x%lx", lowcore_offset_for_refbk);
> +
> + assert((unsigned long)&prefix_buf < SZ_2G);
> +
> + memcpy(prefix_buf, 0, LC_SIZE);
> +
> + /*
> + * After the call to set_prefix() below, this will refer to absolute
> + * address lowcore_offset_for_refbk (reverse prefixing).
> + */
> + refbk_in_reverse_prefix = (struct pfault_refbk *)(&prefix_buf[0] + lowcore_offset_for_refbk);
> +
> + /*
> + * After the call to set_prefix() below, this will refer to absolute
> + * address &prefix_buf[0] + lowcore_offset_for_refbk (forward prefixing).
> + */
> + refbk_in_prefix = (struct pfault_refbk *)OPAQUE_PTR(lowcore_offset_for_refbk);
> +
> + old_prefix = get_prefix();
> + set_prefix((uint32_t)(uintptr_t)prefix_buf);
> +
> + /*
> + * If diag258 would not be applying prefixing on access to
> + * refbk_in_reverse_prefix correctly, it would access absolute address
> + * refbk_in_reverse_prefix (which to us is accessible at real address
> + * refbk_in_prefix).
> + * Make sure it really fails by putting invalid function code
> + * at refbk_in_prefix.
> + */
> + refbk_in_prefix->refdiagc = 0xc0fe;
> +
> + /*
> + * Put a valid refbk at refbk_in_reverse_prefix.
> + */
> + memcpy(refbk_in_reverse_prefix, &pfault_init_refbk, sizeof(pfault_init_refbk));
> +
> + ry = diag258(refbk_in_reverse_prefix);
> + report(!ry, "real address refbk accessed");
> +
> + /*
> + * Activating should have worked. Cancel the activation and expect
> + * return 0. If activation would not have worked, this should return with
> + * 4 (pfault handshaking not active).
> + */
> + ry = diag258(&pfault_cancel_refbk);
> + report(!ry, "handshaking canceled");
> +
> + set_prefix(old_prefix);
> +
> + report_prefix_pop();
> +}
> +
> +/*
> + * Verify that a refbk exceeding physical memory is not accepted, even
> + * when crossing a frame boundary.
> + */
> +static void test_refbk_crossing(void)
> +{
> + const size_t bytes_in_last_page = 8;
> + struct pfault_refbk *refbk = (struct pfault_refbk *)(get_ram_size() - bytes_in_last_page);
> +
> + report_prefix_push("refbk crossing");
> +
> + report_info("refbk is at 0x%lx", (u64)refbk);
> + report_info("ram size is 0x%lx", get_ram_size());
> + assert(sizeof(struct pfault_refbk) > bytes_in_last_page);
> +
> + /* Copy bytes_in_last_page bytes of the init refbk to the page */
> + memcpy(refbk, &pfault_init_refbk, bytes_in_last_page);
> +
> + expect_pgm_int();
> + diag258(refbk);
> + check_pgm_int_code(PGM_INT_CODE_ADDRESSING);
> + report_prefix_pop();
> +}
> +
> +/*
> + * Verify that a refbk with an invalid refdiagc is not accepted.
> + */
> +static void test_refbk_invalid_diagcode(void)
> +{
> + struct pfault_refbk refbk __attribute__((aligned(8))) = pfault_init_refbk;
> +
> + report_prefix_push("invalid refdiagc");
> + refbk.refdiagc = 0xc0fe;
> +
> + expect_pgm_int();
> + diag258(&refbk);
> + check_pgm_int_code(PGM_INT_CODE_SPECIFICATION);
> + report_prefix_pop();
> +}
> +
> +int main(void)
> +{
> + report_prefix_push("diag258");
> +
> + expect_pgm_int();
> + diag258((struct pfault_refbk *)0xfffffffffffffff0);
> + if (clear_pgm_int() == PGM_INT_CODE_SPECIFICATION) {
> + report_skip("diag258 not supported");
> + } else {
> + test_priv();
> + /* Other tests rely on invalid diagcodes doing nothing */
> + test_refbk_invalid_diagcode();
> + test_refbk_real();
> + test_refbk_prefixing();
> + test_refbk_crossing();
> + }
> +
> + report_prefix_pop();
> + return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 3a9decc932f2..8131ba105d3f 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -392,3 +392,6 @@ file = sie-dat.elf
>
> [pv-attest]
> file = pv-attest.elf
> +
> +[diag258]
> +file = diag258.elf
