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Date:   Tue, 31 Jan 2023 09:57:24 +0100
From:   Joerg Roedel <joro@8bytes.org>
To:     "H. Peter Anvin" <hpa@zytor.com>
Cc:     Alexey Kardashevskiy <aik@amd.com>,
        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>,
        Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [Question PATCH kernel] x86/amd/sev/nmi+vc: Fix stack handling
 (why is this happening?)
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On Mon, Jan 30, 2023 at 09:30:38AM -0800, H. Peter Anvin wrote:
> It's somewhat odd to me that reading %dr7 is volatile, but %dr6 is
> not... %dr6 is the status register!

The reason is that on SEV-ES only accesses to DR7 will cause #VC
exceptions, DR0-DR6 are not intercepted.

Regards,

	Joerg