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From: Joerg Roedel <joro@8bytes.org>
To: Alexey Kardashevskiy <aik@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	kvm@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Sean Christopherson <seanjc@google.com>,
	Jiri Kosina <jkosina@suse.cz>, Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [Question PATCH kernel] x86/amd/sev/nmi+vc: Fix stack handling (why is this happening?)
Date: Fri, 27 Jan 2023 18:25:08 +0100	[thread overview]
Message-ID: <Y9QI9JwCVvRmtbr+@8bytes.org> (raw)
In-Reply-To: <b7880f0b-a592-cf2d-03b9-1ccfd83f8223@amd.com>

On Fri, Jan 27, 2023 at 10:56:26PM +1100, Alexey Kardashevskiy wrote:
> https://github.com/aik/linux/commit/d0d6bbb58fcd927ddd1f8e9d42ab121920c7eafc

Okay, I reproduced the problem here and the root cause turned out to be
that the compiler moved the DR7 read instruction before the 5-byte NOP
which becomes the call to sev_es_ist_enter() in SEV-ES guests. This is
guaranteed to cause #VC exception stack recursion if the NMI was
triggered on the #VC stack, and that leads to all kinds of undefined
behavior.

Regards,

	Joerg

  parent reply	other threads:[~2023-01-27 17:25 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-27  3:56 [Question PATCH kernel] x86/amd/sev/nmi+vc: Fix stack handling (why is this happening?) Alexey Kardashevskiy
2023-01-27  9:08 ` Peter Zijlstra
2023-01-27 10:37   ` Joerg Roedel
2023-01-27 11:56     ` Alexey Kardashevskiy
2023-01-27 12:59       ` Joerg Roedel
2023-01-27 17:25       ` Joerg Roedel [this message]
2023-01-28 11:24         ` Alexey Kardashevskiy
2023-01-28 13:52           ` Joerg Roedel
2023-01-30  9:17             ` Joerg Roedel
2023-01-30 17:30           ` H. Peter Anvin
2023-01-30 18:04             ` Borislav Petkov
2023-01-31  8:57             ` Joerg Roedel
2023-01-31 15:53               ` Sean Christopherson
2023-01-31 16:00                 ` Joerg Roedel
2023-01-31 16:47                   ` Sean Christopherson
2023-01-27 12:13   ` Alexey Kardashevskiy
2023-01-27 12:41     ` Peter Zijlstra
2023-01-31 10:37 ` [tip: x86/urgent] x86/debug: Fix stack recursion caused by wrongly ordered DR7 accesses tip-bot2 for Joerg Roedel
2023-01-31 11:57 ` tip-bot2 for Joerg Roedel

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