From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
"berto@igalia.com" <berto@igalia.com>,
"ehabkost@redhat.com" <ehabkost@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Denis Lunev <den@virtuozzo.com>,
"mtosatti@redhat.com" <mtosatti@redhat.com>,
"mdroth@linux.vnet.ibm.com" <mdroth@linux.vnet.ibm.com>,
"armbru@redhat.com" <armbru@redhat.com>,
"rth@twiddle.net" <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH 3/3] i386/kvm: initialize struct at full before ioctl call
Date: Wed, 31 Jul 2019 14:28:17 +0200 [thread overview]
Message-ID: <bdbee2e0-62a7-8906-8076-408922511146@de.ibm.com> (raw)
In-Reply-To: <08958a7e-1952-caf7-ab45-2fd503db418c@virtuozzo.com>
On 31.07.19 14:04, Andrey Shinkevich wrote:
> On 31/07/2019 10:24, Christian Borntraeger wrote:
>>
>>
>> On 30.07.19 21:20, Paolo Bonzini wrote:
>>> On 30/07/19 18:01, Andrey Shinkevich wrote:
>>>> Not the whole structure is initialized before passing it to the KVM.
>>>> Reduce the number of Valgrind reports.
>>>>
>>>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>>>
>>> Christian, is this the right fix? It's not expensive so it wouldn't be
>>> an issue, just checking if there's any better alternative.
>>
>> I think all of these variants are valid with pros and cons
>> 1. teach valgrind about this:
>> Add to coregrind/m_syswrap/syswrap-linux.c (and the relevant header files)
>> knowledge about which parts are actually touched.
>> 2. use designated initializers
>> 3. use memset
>> 3. use a valgrind callback VG_USERREQ__MAKE_MEM_DEFINED to tell that this memory is defined
>>
>
> Thank you all very much for taking part in the discussion.
> Also, one may use the Valgrind technology to suppress the unwanted
> reports by adding the Valgrind specific format file valgrind.supp to the
> QEMU project. The file content is extendable for future needs.
> All the cases we like to suppress will be recounted in that file.
> A case looks like the stack fragments. For instance, from QEMU block:
>
> {
> hw/block/hd-geometry.c
> Memcheck:Cond
> fun:guess_disk_lchs
> fun:hd_geometry_guess
> fun:blkconf_geometry
> ...
> fun:device_set_realized
> fun:property_set_bool
> fun:object_property_set
> fun:object_property_set_qobject
> fun:object_property_set_bool
> }
>
> The number of suppressed cases are reported by the Valgrind with every
> run: "ERROR SUMMARY: 5 errors from 3 contexts (suppressed: 0 from 0)"
>
> Andrey
Yes, indeed that would be another variant. How performance critical are
the fixed locations? That might have an impact on what is the best solution.
From a cleanliness approach doing 1 (adding the ioctl definition to valgrind)
is certainly the most beautiful way. I did that in the past, look for example at
https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=c2baee9b7bf043702c130de0771a4df439fcf403
or
https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=00a31dd3d1e7101b331c2c83fca6c666ba35d910
for examples.
>
>>>
>>> Paolo
>>>
>>>> ---
>>>> target/i386/kvm.c | 3 +++
>>>> 1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
>>>> index dbbb137..ed57e31 100644
>>>> --- a/target/i386/kvm.c
>>>> +++ b/target/i386/kvm.c
>>>> @@ -190,6 +190,7 @@ static int kvm_get_tsc(CPUState *cs)
>>>> return 0;
>>>> }
>>>>
>>>> + memset(&msr_data, 0, sizeof(msr_data));
>>>> msr_data.info.nmsrs = 1;
>>>> msr_data.entries[0].index = MSR_IA32_TSC;
>>>> env->tsc_valid = !runstate_is_running();
>>>> @@ -1706,6 +1707,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
>>>>
>>>> if (has_xsave) {
>>>> env->xsave_buf = qemu_memalign(4096, sizeof(struct kvm_xsave));
>>>> + memset(env->xsave_buf, 0, sizeof(struct kvm_xsave));
>>>> }
>>>>
>>>> max_nested_state_len = kvm_max_nested_state_length();
>>>> @@ -3477,6 +3479,7 @@ static int kvm_put_debugregs(X86CPU *cpu)
>>>> return 0;
>>>> }
>>>>
>>>> + memset(&dbgregs, 0, sizeof(dbgregs));
>>>> for (i = 0; i < 4; i++) {
>>>> dbgregs.db[i] = env->dr[i];
>>>> }
>>>> --
>>>> 1.8.3.1
>>>>
>>>
>>>
>>
>
next prev parent reply other threads:[~2019-07-31 12:29 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 16:01 [Qemu-devel] [PATCH 0/3] Reduce the number of Valgrind reports in unit tests Andrey Shinkevich
2019-07-30 16:01 ` [Qemu-devel] [PATCH 1/3] test-throttle: Fix uninitialized use of burst_length Andrey Shinkevich
2019-08-13 12:19 ` Alberto Garcia
2019-07-30 16:01 ` [Qemu-devel] [PATCH 2/3] tests: Fix uninitialized byte in test_visitor_in_fuzz Andrey Shinkevich
2019-07-30 16:01 ` [Qemu-devel] [PATCH 3/3] i386/kvm: initialize struct at full before ioctl call Andrey Shinkevich
2019-07-30 16:44 ` Philippe Mathieu-Daudé
2019-07-30 17:05 ` Christian Borntraeger
2019-07-30 17:14 ` Philippe Mathieu-Daudé
2019-07-30 17:47 ` Christian Borntraeger
2019-07-31 9:05 ` Christophe de Dinechin
2019-07-31 12:32 ` Paolo Bonzini
2019-07-31 14:10 ` Andrey Shinkevich
2019-07-30 19:22 ` Paolo Bonzini
2019-07-30 16:46 ` Peter Maydell
2019-07-30 17:09 ` Christian Borntraeger
2019-07-30 19:20 ` Paolo Bonzini
2019-07-31 7:24 ` Christian Borntraeger
2019-07-31 12:04 ` Andrey Shinkevich
2019-07-31 12:28 ` Christian Borntraeger [this message]
2019-07-31 12:43 ` Christian Borntraeger
2019-07-31 13:03 ` Paolo Bonzini
2019-07-31 14:11 ` Andrey Shinkevich
2019-08-13 12:02 ` [Qemu-devel] [PATCH 0/3] Reduce the number of Valgrind reports in unit tests Andrey Shinkevich
2019-08-13 12:05 ` Paolo Bonzini
2019-08-13 12:08 ` Andrey Shinkevich
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