RE: [EXTERNAL] Re: [PATCH] x86/tdx: Generate SIGBUS on userspace MMIO

[Chris Oo]

We use this to handle MMIO issued by userspace that the kernel does not handle in a #VE, for devices assigned to a TDX VM. 

Chris

-----Original Message-----
From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> 
Sent: Thursday, May 23, 2024 3:15 AM
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>; x86@xxxxxxxxxx; H. Peter Anvin <hpa@xxxxxxxxx>; linux-coco@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Chris Oo <cho@xxxxxxxxxxxxx>; Dexuan Cui <decui@xxxxxxxxxxxxx>; John Starks <John.Starks@xxxxxxxxxxxxx>
Subject: [EXTERNAL] Re: [PATCH] x86/tdx: Generate SIGBUS on userspace MMIO

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