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Message-ID: <3e9a26c3-8eee-88f5-f8e2-8a2dd2c028ea@intel.com>
Date: Fri, 7 May 2021 14:52:21 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...nel.org>,
Dan Williams <dan.j.williams@...el.com>,
Tony Luck <tony.luck@...el.com>
Cc: Andi Kleen <ak@...ux.intel.com>,
Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
Raj Ashok <ashok.raj@...el.com>,
Sean Christopherson <seanjc@...gle.com>,
linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 15/32] x86/tdx: Handle in-kernel MMIO
On 4/26/21 11:01 AM, Kuppuswamy Sathyanarayanan wrote:
> Handle #VE due to MMIO operations. MMIO triggers #VE with EPT_VIOLATION
> exit reason.
This needs a bit of a history lesson. "In traditional VMs, MMIO tends
to be implemented by giving a guest access to an mapping which will
cause a VMEXIT on access. That's not possible in a TDX guest..."
> For now we only handle subset of instruction that kernel uses for MMIO
> oerations. User-space access triggers SIGBUS.
I still don't think that TDX guests should be doing things that they
*KNOW* will cause #VE, including MMIO. I really want to hear a more
discrete story about why this is the *best* way to do this for Linux
instead of just a hack from the Windows binary driver ecosystem that
seemed expedient.
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