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From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Michael Tokarev <mjt@tls.msk.ru>,
	Sven Schnelle <svens@linux.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [PATCH v3 9/9] KVM: Move instrumentation-safe annotations for enter/exit to x86 code
Date: Wed, 21 Apr 2021 10:09:11 +0200
Message-ID: <0c74158d-279a-5afa-0778-822c77ac8dc2@de.ibm.com> (raw)
In-Reply-To: <20210415222106.1643837-10-seanjc@google.com>



On 16.04.21 00:21, Sean Christopherson wrote:
> Drop the instrumentation_{begin,end}() annonations from the common KVM
> guest enter/exit helpers, and massage the x86 code as needed to preserve
> the necessary annotations.  x86 is the only architecture whose transition
> flow is tagged as noinstr, and more specifically, it is the only
> architecture for which instrumentation_{begin,end}() can be non-empty.
> 
> No other architecture supports CONFIG_STACK_VALIDATION=y, and s390 is the
> only other architecture that support CONFIG_DEBUG_ENTRY=y.  For
> instrumentation annontations to be meaningful, both aformentioned configs
> must be enabled.
> 
> Letting x86 deal with the annotations avoids unnecessary nops by
> squashing back-to-back instrumention-safe sequences.

We have considered implementing objtool for s390. Not sure where we
stand and if we will do this or not. Sven/Heiko?

So maybe drop this patch until every other arch agrees that there are
no plans to implement this.

  reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15 22:20 [PATCH v3 0/9] KVM: Fix tick-based accounting for x86 guests Sean Christopherson
2021-04-15 22:20 ` [PATCH v3 1/9] context_tracking: Move guest exit context tracking to separate helpers Sean Christopherson
2021-04-20 18:48   ` Christian Borntraeger
2021-04-21 10:57   ` Frederic Weisbecker
2021-04-15 22:20 ` [PATCH v3 2/9] context_tracking: Move guest exit vtime accounting " Sean Christopherson
2021-04-20 18:48   ` Christian Borntraeger
2021-04-15 22:21 ` [PATCH v3 3/9] KVM: x86: Defer tick-based accounting 'til after IRQ handling Sean Christopherson
2021-04-20 23:14   ` Frederic Weisbecker
2021-04-20 23:26     ` Sean Christopherson
2021-04-21 10:11       ` Frederic Weisbecker
2021-04-21 12:19       ` Frederic Weisbecker
2021-04-28 22:38         ` Sean Christopherson
2021-04-21 10:07   ` Frederic Weisbecker
2021-04-15 22:21 ` [PATCH v3 4/9] sched/vtime: Move vtime accounting external declarations above inlines Sean Christopherson
2021-04-21  7:02   ` Christian Borntraeger
2021-04-15 22:21 ` [PATCH v3 5/9] sched/vtime: Move guest enter/exit vtime accounting to vtime.h Sean Christopherson
2021-04-15 22:21 ` [PATCH v3 6/9] context_tracking: Consolidate guest enter/exit wrappers Sean Christopherson
2021-04-15 22:21 ` [PATCH v3 7/9] context_tracking: KVM: Move guest enter/exit wrappers to KVM's domain Sean Christopherson
2021-04-21  7:10   ` Christian Borntraeger
2021-04-15 22:21 ` [PATCH v3 8/9] KVM: x86: Consolidate guest enter/exit logic to common helpers Sean Christopherson
2021-04-15 22:21 ` [PATCH v3 9/9] KVM: Move instrumentation-safe annotations for enter/exit to x86 code Sean Christopherson
2021-04-21  8:09   ` Christian Borntraeger [this message]
2021-04-22 14:38     ` Sven Schnelle
2021-04-23  9:32       ` Vasily Gorbik
2021-04-20 23:33 ` [PATCH v3 0/9] KVM: Fix tick-based accounting for x86 guests Frederic Weisbecker

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