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From: Chris Oo <cho@microsoft.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Kuppuswamy
 Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
CC: Dave Hansen <dave.hansen@linux.intel.com>, Thomas Gleixner
	<tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
	<bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>, "H. Peter Anvin"
	<hpa@zytor.com>, "linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Dexuan Cui
	<decui@microsoft.com>, John Starks <John.Starks@microsoft.com>
Subject: RE: [EXTERNAL] Re: [PATCH] x86/tdx: Generate SIGBUS on userspace MMIO
Thread-Topic: [EXTERNAL] Re: [PATCH] x86/tdx: Generate SIGBUS on userspace
 MMIO
Thread-Index: AQHaq4POpB86nlvWk0KLe74GGBU5r7GknPgAgABzPFA=
Date: Thu, 23 May 2024 17:08:40 +0000
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We use this to handle MMIO issued by userspace that the kernel does not han=
dle in a #VE, for devices assigned to a TDX VM.=20

Chris

-----Original Message-----
From: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>=20
Sent: Thursday, May 23, 2024 3:15 AM
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>; Thomas Gleixner <tglx@linutr=
onix.de>; Ingo Molnar <mingo@redhat.com>; Borislav Petkov <bp@alien8.de>; x=
86@kernel.org; H. Peter Anvin <hpa@zytor.com>; linux-coco@lists.linux.dev; =
linux-kernel@vger.kernel.org; Chris Oo <cho@microsoft.com>; Dexuan Cui <dec=
ui@microsoft.com>; John Starks <John.Starks@microsoft.com>
Subject: [EXTERNAL] Re: [PATCH] x86/tdx: Generate SIGBUS on userspace MMIO

On Tue, May 21, 2024 at 06:35:49AM -0700, Kuppuswamy Sathyanarayanan wrote:
>=20
> On 5/21/24 12:35 AM, Kirill A. Shutemov wrote:
> > Currently attempt to do MMIO from userspace in TDX guest leads to=20
> > warning about unexpect #VE and SIGSEGV being delivered to the process.
> >
> > Enlightened userspace might choose to deal with MMIO on their own if=20
> > kernel doesn't emulate it.
>=20
> Any specific use cases ? Like who is using it?

Microsoft folks wanted it. Chris, Dexuan, John, any comments?

But it is generally right thing to do. SIGBUS is right signal to deliver.

--
  Kiryl Shutsemau / Kirill A. Shutemov