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Tue, 5 Oct 2021 13:32:34 +0000 (GMT) Subject: Re: [kvm-unit-tests PATCH v2 1/5] s390x: Add specification exception test To: Janosch Frank , Janis Schoetterl-Glausch , Thomas Huth Cc: Cornelia Huck , Claudio Imbrenda , David Hildenbrand , kvm@vger.kernel.org, linux-s390@vger.kernel.org References: <20211005090921.1816373-1-scgl@linux.ibm.com> <20211005090921.1816373-2-scgl@linux.ibm.com> From: Janis Schoetterl-Glausch Message-ID: Date: Tue, 5 Oct 2021 15:32:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: FiBFxoGXoIfe0xjeiv60t4ycY5k52xDt X-Proofpoint-ORIG-GUID: 1lROETXjlQVafs5obzSccf7na5iRLlPY X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-10-05_02,2021-10-04_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 bulkscore=0 mlxscore=0 malwarescore=0 priorityscore=1501 impostorscore=0 clxscore=1015 suspectscore=0 adultscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2110050080 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 10/5/21 1:56 PM, Janosch Frank wrote: > On 10/5/21 11:09, Janis Schoetterl-Glausch wrote: >> Generate specification exceptions and check that they occur. >> With the iterations argument one can check if specification >> exception interpretation occurs, e.g. by using a high value and >> checking that the debugfs counters are substantially lower. >> The argument is also useful for estimating the performance benefit >> of interpretation. >> >> Signed-off-by: Janis Schoetterl-Glausch >> --- >>   s390x/Makefile      |   1 + >>   s390x/spec_ex.c     | 182 ++++++++++++++++++++++++++++++++++++++++++++ >>   s390x/unittests.cfg |   3 + >>   3 files changed, 186 insertions(+) >>   create mode 100644 s390x/spec_ex.c >> >> diff --git a/s390x/Makefile b/s390x/Makefile >> index ef8041a..57d7c9e 100644 >> --- a/s390x/Makefile >> +++ b/s390x/Makefile >> @@ -24,6 +24,7 @@ tests += $(TEST_DIR)/mvpg.elf >>   tests += $(TEST_DIR)/uv-host.elf >>   tests += $(TEST_DIR)/edat.elf >>   tests += $(TEST_DIR)/mvpg-sie.elf >> +tests += $(TEST_DIR)/spec_ex.elf >>     tests_binary = $(patsubst %.elf,%.bin,$(tests)) >>   ifneq ($(HOST_KEY_DOCUMENT),) >> diff --git a/s390x/spec_ex.c b/s390x/spec_ex.c >> new file mode 100644 >> index 0000000..dd0ee53 >> --- /dev/null >> +++ b/s390x/spec_ex.c >> @@ -0,0 +1,182 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * © Copyright IBM Corp. 2021 >> + * >> + * Specification exception test. >> + * Tests that specification exceptions occur when expected. >> + */ >> +#include >> +#include >> +#include >> +#include >> + >> +static struct lowcore *lc = (struct lowcore *) 0; >> + >> +static bool expect_invalid_psw; >> +static struct psw expected_psw; >> +static struct psw fixup_psw; >> + >> +/* The standard program exception handler cannot deal with invalid old PSWs, >> + * especially not invalid instruction addresses, as in that case one cannot >> + * find the instruction following the faulting one from the old PSW. >> + * The PSW to return to is set by load_psw. >> + */ >> +static void fixup_invalid_psw(void) >> +{ >> +    if (expect_invalid_psw) { >> +        report(expected_psw.mask == lc->pgm_old_psw.mask >> +               && expected_psw.addr == lc->pgm_old_psw.addr, >> +               "Invalid program new PSW as expected"); >> +        expect_invalid_psw = false; >> +    } >> +    lc->pgm_old_psw = fixup_psw; >> +} >> + >> +static void load_psw(struct psw psw) >> +{ >> +    uint64_t r0 = 0, r1 = 0; >> + >> +    asm volatile ( >> +        "    epsw    %0,%1\n" >> +        "    st    %0,%[mask]\n" >> +        "    st    %1,4+%[mask]\n" > > You're grabbing the mask for the fixup psw, right? Yes > Why don't you use the extract_psw_mask() function for that? No reason, sounds like a good idea to use the function. > > Also I'd recommend not mixing named operands and numeric operands, especially when the variables are then called r0 and r1. I suppose I didn't name them because they're just scratch registers. But using extract_psw_mask() will get rid of them anyway > >> +        "    larl    %0,nop%=\n" >> +        "    stg    %0,%[addr]\n" > > This stores the address of the nop to the fixup psw addr. > So far so good, but why is it only called "addr"? > >> +        "    lpswe    %[psw]\n" >> +        "nop%=:    nop\n" >> +        : "+&r"(r0), "+&a"(r1), [mask] "=&R"(fixup_psw.mask), >> +          [addr] "=&R"(fixup_psw.addr) >> +        : [psw] "Q"(psw) >> +        : "cc", "memory" >> +    ); > > You made this a bit complicated and didn't document it. > /* >  * Setup fixup_psw before loading an invalid PSW so that *fixup_invalid_psw() can bring us back onto the right track. >  */ > >> +} >> + >> +static void psw_bit_12_is_1(void) >> +{ >> +    expected_psw.mask = 0x0008000000000000; >> +    expected_psw.addr = 0x00000000deadbeee; >> +    expect_invalid_psw = true; >> +    load_psw(expected_psw); >> +} >> + [...]