From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Kieran Bingham <kbingham@kernel.org>,
Jan Kiszka <jan.kiszka@siemens.com>,
Andrew Jones <drjones@redhat.com>,
Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Johannes Berg <johannes.berg@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
"H. Peter Anvin" <hpa@zytor.com>, Jessica Yu <jeyu@kernel.org>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Yang Weijiang <weijiang.yang@intel.com>,
linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Shuah Khan <shuah@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v3 6/6] KVM: selftests: test KVM_GUESTDBG_BLOCKIRQ
Date: Tue, 02 Nov 2021 11:46:54 +0100 [thread overview]
Message-ID: <87k0hqkf6p.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <YYB2l9bzFhKzobZB@google.com>
Sean Christopherson <seanjc@google.com> writes:
> On Mon, Nov 01, 2021, Maxim Levitsky wrote:
>> On Mon, 2021-11-01 at 16:43 +0100, Vitaly Kuznetsov wrote:
>> > Paolo Bonzini <pbonzini@redhat.com> writes:
>> >
>> > > On 11/08/21 14:29, Maxim Levitsky wrote:
>> > > > Modify debug_regs test to create a pending interrupt
>> > > > and see that it is blocked when single stepping is done
>> > > > with KVM_GUESTDBG_BLOCKIRQ
>> > > >
>> > > > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>> > > > ---
>> > > > .../testing/selftests/kvm/x86_64/debug_regs.c | 24 ++++++++++++++++---
>> > > > 1 file changed, 21 insertions(+), 3 deletions(-)
>> > >
>> > > I haven't looked very much at this, but the test fails.
>> > >
>> >
>> > Same here,
>> >
>> > the test passes on AMD but fails consistently on Intel:
>> >
>> > # ./x86_64/debug_regs
>> > ==== Test Assertion Failure ====
>> > x86_64/debug_regs.c:179: run->exit_reason == KVM_EXIT_DEBUG && run->debug.arch.exception == DB_VECTOR && run->debug.arch.pc == target_rip && run->debug.arch.dr6 == target_dr6
>> > pid=13434 tid=13434 errno=0 - Success
>> > 1 0x00000000004027c6: main at debug_regs.c:179
>> > 2 0x00007f65344cf554: ?? ??:0
>> > 3 0x000000000040294a: _start at ??:?
>> > SINGLE_STEP[1]: exit 8 exception 1 rip 0x402a25 (should be 0x402a27) dr6 0xffff4ff0 (should be 0xffff4ff0)
>> >
>> > (I know I'm late to the party).
>>
>> Well that is strange. It passes on my intel laptop. Just tested
>> (kvm/queue + qemu master, compiled today) :-(
>>
>> It fails on iteration 1 (and there is iteration 0) which I think means that we
>> start with RIP on sti, and get #DB on start of xor instruction first (correctly),
>> and then we get #DB again on start of xor instruction again?
>>
>> Something very strange. My laptop has i7-7600U.
>
> I haven't verified on hardware, but my guess is that this code in vmx_vcpu_run()
>
> /* When single-stepping over STI and MOV SS, we must clear the
> * corresponding interruptibility bits in the guest state. Otherwise
> * vmentry fails as it then expects bit 14 (BS) in pending debug
> * exceptions being set, but that's not correct for the guest debugging
> * case. */
> if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
> vmx_set_interrupt_shadow(vcpu, 0);
>
> interacts badly with APICv=1. It will kill the STI shadow and cause the IRQ in
> vmcs.GUEST_RVI to be recognized when it (micro-)architecturally should not. My
> head is going in circles trying to sort out what would actually happen. Maybe
> comment out that and/or disable APICv to see if either one makes the test pass?
>
Interestingly,
loading 'kvm-intel' with 'enable_apicv=0' makes the test pass, however,
commenting out "vmx_set_interrupt_shadow()" as suggested gives a
different result (with enable_apicv=1):
# ./x86_64/debug_regs
==== Test Assertion Failure ====
x86_64/debug_regs.c:179: run->exit_reason == KVM_EXIT_DEBUG && run->debug.arch.exception == DB_VECTOR && run->debug.arch.pc == target_rip && run->debug.arch.dr6 == target_dr6
pid=16352 tid=16352 errno=0 - Success
1 0x0000000000402b33: main at debug_regs.c:179 (discriminator 10)
2 0x00007f36401bd554: ?? ??:0
3 0x00000000004023a9: _start at ??:?
SINGLE_STEP[1]: exit 9 exception -2147483615 rip 0x1 (should be 0x4024d9) dr6 0xffff4ff0 (should be 0xffff4ff0)
this is a fairly old "Intel(R) Xeon(R) CPU E5-2603 v3".
--
Vitaly
next prev parent reply other threads:[~2021-11-02 10:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 12:29 [PATCH v3 0/6] KVM: my debug patch queue Maxim Levitsky
2021-08-11 12:29 ` [PATCH v3 1/6] KVM: SVM: split svm_handle_invalid_exit Maxim Levitsky
2021-08-11 12:29 ` [PATCH v3 2/6] KVM: x86: add force_intercept_exceptions_mask Maxim Levitsky
2021-09-02 16:56 ` Sean Christopherson
2022-02-08 14:34 ` Maxim Levitsky
2022-03-08 23:37 ` Sean Christopherson
2022-03-09 12:31 ` Maxim Levitsky
2022-03-09 14:03 ` Paolo Bonzini
2022-03-09 15:40 ` Sean Christopherson
2021-08-11 12:29 ` [PATCH v3 3/6] KVM: SVM: implement force_intercept_exceptions_mask Maxim Levitsky
2021-08-11 14:26 ` Maxim Levitsky
2021-09-02 17:34 ` Sean Christopherson
2022-02-08 14:35 ` Maxim Levitsky
2021-08-11 12:29 ` [PATCH v3 4/6] scripts/gdb: rework lx-symbols gdb script Maxim Levitsky
2021-08-11 12:29 ` [PATCH v3 5/6] KVM: x86: implement KVM_GUESTDBG_BLOCKIRQ Maxim Levitsky
2021-08-11 12:29 ` [PATCH v3 6/6] KVM: selftests: test KVM_GUESTDBG_BLOCKIRQ Maxim Levitsky
2021-09-06 11:20 ` Paolo Bonzini
2021-09-06 21:03 ` Maxim Levitsky
2021-11-01 15:43 ` Vitaly Kuznetsov
2021-11-01 16:19 ` Maxim Levitsky
2021-11-01 23:21 ` Sean Christopherson
2021-11-02 10:46 ` Vitaly Kuznetsov [this message]
2021-11-02 15:53 ` Sean Christopherson
2021-11-02 16:18 ` Vitaly Kuznetsov
2021-11-02 18:45 ` Sean Christopherson
2021-11-03 9:04 ` Maxim Levitsky
2021-08-11 13:10 ` [PATCH v3 0/6] KVM: my debug patch queue Paolo Bonzini
2021-08-11 13:22 ` Maxim Levitsky
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87k0hqkf6p.fsf@vitty.brq.redhat.com \
--to=vkuznets@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=drjones@redhat.com \
--cc=hpa@zytor.com \
--cc=jan.kiszka@siemens.com \
--cc=jeyu@kernel.org \
--cc=jmattson@google.com \
--cc=johannes.berg@intel.com \
--cc=joro@8bytes.org \
--cc=kbingham@kernel.org \
--cc=kvm@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=mlevitsk@redhat.com \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=wanpengli@tencent.com \
--cc=weijiang.yang@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).