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From: Maxim Levitsky <mlevitsk@redhat.com>
To: Sean Christopherson <seanjc@google.com>, Joerg Roedel <joro@8bytes.org>
Cc: kvm@vger.kernel.org, Vitaly Kuznetsov <vkuznets@redhat.com>,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Wanpeng Li <wanpengli@tencent.com>,
	Kieran Bingham <kbingham@kernel.org>,
	Jessica Yu <jeyu@kernel.org>, Jan Kiszka <jan.kiszka@siemens.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, Jim Mattson <jmattson@google.com>,
	Borislav Petkov <bp@alien8.de>,
	Stefano Garzarella <sgarzare@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@suse.de>
Subject: Re: [PATCH 3/3] KVM: SVM: allow to intercept all exceptions for debug
Date: Thu, 18 Mar 2021 18:41:57 +0200	[thread overview]
Message-ID: <7169229dde171c8e10fb276ff8e1a869af99b39d.camel@redhat.com> (raw)
In-Reply-To: <YFOBTITk7EkGdzR2@google.com>

On Thu, 2021-03-18 at 16:35 +0000, Sean Christopherson wrote:
> On Thu, Mar 18, 2021, Joerg Roedel wrote:
> > On Thu, Mar 18, 2021 at 11:24:25AM +0200, Maxim Levitsky wrote:
> > > But again this is a debug feature, and it is intended to allow the user
> > > to shoot himself in the foot.
> > 
> > And one can't debug SEV-ES guests with it, so what is the point of
> > enabling it for them too?
You can create a special SEV-ES guest which does handle all exceptions via
#VC, or just observe it fail which can be useful for some whatever reason.
> 
> Agreed.  I can see myself enabling debug features by default, it would be nice
> to not having to go out of my way to disable them for SEV-ES/SNP guests.
This does sound like a valid reason to disable this for SEV-ES.

> 
> Skipping SEV-ES guests should not be difficult; KVM could probably even
> print a message stating that the debug hook is being ignored.  One thought would
> be to snapshot debug_intercept_exceptions at VM creation, and simply zero it out
> for incompatible guests.  That would also allow changing debug_intercept_exceptions
> without reloading KVM, which IMO would be very convenient.
> 
So all right I'll disable this for SEV-ES. 
The idea to change the debug_intercept_exceptions on the fly is also a good idea,
I will implement it in next version of the patches.

Thanks for the review,
Best regards,
	Maxim Levitsky


  reply	other threads:[~2021-03-18 16:43 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-15 22:10 [PATCH 0/3] KVM: my debug patch queue Maxim Levitsky
2021-03-15 22:10 ` [PATCH 1/3] scripts/gdb: rework lx-symbols gdb script Maxim Levitsky
2021-03-16 13:38   ` Jan Kiszka
2021-03-16 14:12     ` Maxim Levitsky
2021-03-15 22:10 ` [PATCH 2/3] KVM: x86: guest debug: don't inject interrupts while single stepping Maxim Levitsky
2021-03-15 23:37   ` Sean Christopherson
2021-03-16  9:16     ` Jan Kiszka
2021-03-16 10:59       ` Maxim Levitsky
2021-03-16 11:27         ` Jan Kiszka
2021-03-16 12:34           ` Maxim Levitsky
2021-03-16 13:46             ` Jan Kiszka
2021-03-16 14:34               ` Maxim Levitsky
2021-03-16 15:31                 ` Jan Kiszka
     [not found]                   ` <e2cd978e357155dbab21a523bb8981973bd10da7.camel@redhat.com>
2021-03-16 15:56                     ` Jan Kiszka
2021-03-16 16:50                     ` Sean Christopherson
2021-03-16 17:01                       ` Jan Kiszka
2021-03-16 17:26                         ` Sean Christopherson
2021-03-17  9:20                           ` Jan Kiszka
2021-03-16 18:02                         ` Maxim Levitsky
2021-03-18 16:02                           ` Jan Kiszka
2021-03-18 12:21             ` Jan Kiszka
2021-03-16 10:55     ` Maxim Levitsky
2021-03-15 22:10 ` [PATCH 3/3] KVM: SVM: allow to intercept all exceptions for debug Maxim Levitsky
2021-03-16  8:32   ` Joerg Roedel
2021-03-16 10:51     ` Maxim Levitsky
2021-03-18  9:19       ` Joerg Roedel
2021-03-18  9:24         ` Maxim Levitsky
2021-03-18 15:47           ` Joerg Roedel
2021-03-18 16:35             ` Sean Christopherson
2021-03-18 16:41               ` Maxim Levitsky [this message]
2021-03-18 17:22                 ` Sean Christopherson
2021-03-16  8:34   ` Borislav Petkov

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