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From: Sean Christopherson <seanjc@google.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	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>,
	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?)
Date: Tue, 31 Jan 2023 15:53:39 +0000	[thread overview]
Message-ID: <Y9k5g5jYA/rjIwUj@google.com> (raw)
In-Reply-To: <Y9jX9AKYP8H34wGI@8bytes.org>

On Tue, Jan 31, 2023, Joerg Roedel wrote:
> 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.

I don't think that is technically true.  A _well-behaved_ hypervisor will not
intercept DR0-DR6 accesses for SEV-ES guests, but AFAICT nothing in the SEV-ES
architecture enforces that behavior.

  reply	other threads:[~2023-01-31 15:53 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
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 [this message]
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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