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From: Joerg Roedel <jroedel@suse.de>
To: Sean Christopherson <seanjc@google.com>
Cc: Joerg Roedel <joro@8bytes.org>,
	x86@kernel.org, Eric Biederman <ebiederm@xmission.com>,
	kexec@lists.infradead.org, hpa@zytor.com,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Slaby <jslaby@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	David Rientjes <rientjes@google.com>,
	Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mike Stunes <mstunes@vmware.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 11/12] x86/sev: Handle CLFLUSH MMIO events
Date: Sat, 31 Jul 2021 09:17:37 +0200	[thread overview]
Message-ID: <YQT5Ec5M6maZdFoO@suse.de> (raw)
In-Reply-To: <YQSAVo0CXUKHXdLF@google.com>

Hi Sean,

On Fri, Jul 30, 2021 at 10:42:30PM +0000, Sean Christopherson wrote:
> On Wed, Jul 21, 2021, Joerg Roedel wrote:
> This wording can be misread as "the hypervisor is responsible for _all_ cache
> management".  Maybe just:
> 
> 		/*
> 		 * Ignore CLFLUSHes - the hyperivsor is responsible for cache
> 		 * management of emulated MMIO.
> 		 */

Right, will update the comment, thanks.

> Side topic, out of curisoity, what's mapping/accessing emulated MMIO as non-UC?

The CLFLUSHes happen when the kexec'ed kernel maps the VGA framebuffer
as unencrypted. Initially it is mapped encrypted and before re-mapping
the kernel flushes the range from the caches.

I have not investigated why this doesn't happen on the first boot,
though.

Regards,

	Joerg

WARNING: multiple messages have this Message-ID
From: Joerg Roedel <jroedel@suse.de>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	virtualization@lists.linux-foundation.org,
	Arvind Sankar <nivedita@alum.mit.edu>,
	hpa@zytor.com, Jiri Slaby <jslaby@suse.cz>,
	Joerg Roedel <joro@8bytes.org>,
	x86@kernel.org, David Rientjes <rientjes@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Martin Radev <martin.b.radev@gmail.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Kees Cook <keescook@chromium.org>, Cfir Cohen <cfir@google.com>,
	linux-coco@lists.linux.dev, Andy Lutomirski <luto@kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Juergen Gross <jgross@suse.com>, Mike Stunes <mstunes@vmware.com>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	Eric Biederman <ebiederm@xmission.com>,
	Erdem Aktas <erdemaktas@google.com>
Subject: Re: [PATCH 11/12] x86/sev: Handle CLFLUSH MMIO events
Date: Sat, 31 Jul 2021 09:17:37 +0200	[thread overview]
Message-ID: <YQT5Ec5M6maZdFoO@suse.de> (raw)
In-Reply-To: <YQSAVo0CXUKHXdLF@google.com>

Hi Sean,

On Fri, Jul 30, 2021 at 10:42:30PM +0000, Sean Christopherson wrote:
> On Wed, Jul 21, 2021, Joerg Roedel wrote:
> This wording can be misread as "the hypervisor is responsible for _all_ cache
> management".  Maybe just:
> 
> 		/*
> 		 * Ignore CLFLUSHes - the hyperivsor is responsible for cache
> 		 * management of emulated MMIO.
> 		 */

Right, will update the comment, thanks.

> Side topic, out of curisoity, what's mapping/accessing emulated MMIO as non-UC?

The CLFLUSHes happen when the kexec'ed kernel maps the VGA framebuffer
as unencrypted. Initially it is mapped encrypted and before re-mapping
the kernel flushes the range from the caches.

I have not investigated why this doesn't happen on the first boot,
though.

Regards,

	Joerg
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

  reply	other threads:[~2021-07-31  7:17 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21 14:20 [PATCH 00/12] x86/sev: KEXEC/KDUMP support for SEV-ES guests Joerg Roedel
2021-07-21 14:20 ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 01/12] kexec: Allow architecture code to opt-out at runtime Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 02/12] x86/kexec/64: Forbid kexec when running as an SEV-ES guest Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 03/12] x86/sev: Save and print negotiated GHCB protocol version Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 04/12] x86/sev: Do not hardcode " Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 21:17   ` Tom Lendacky
2021-07-21 21:17     ` Tom Lendacky via Virtualization
2021-07-31  7:18     ` Joerg Roedel
2021-07-31  7:18       ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 05/12] x86/sev: Use GHCB protocol version 2 if supported Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 06/12] x86/sev: Cache AP Jump Table Address Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 07/12] x86/sev: Setup code to park APs in the AP Jump Table Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 08/12] x86/sev: Park APs on AP Jump Table with GHCB protocol version 2 Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 09/12] x86/sev: Use AP Jump Table blob to stop CPU Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 10/12] x86/sev: Add MMIO handling support to boot/compressed/ code Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 11/12] x86/sev: Handle CLFLUSH MMIO events Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel
2021-07-30 22:42   ` Sean Christopherson
2021-07-31  7:17     ` Joerg Roedel [this message]
2021-07-31  7:17       ` Joerg Roedel
2021-07-21 14:20 ` [PATCH 12/12] x86/sev: Support kexec under SEV-ES with AP Jump Table blob Joerg Roedel
2021-07-21 14:20   ` Joerg Roedel

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