linux-kernel - RE: [PATCH] x86/tdx: Fix crash on kexec

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Date: Sat, 29 Jun 2024 19:27:57 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Borislav Petkov
	<bp@...en8.de>
CC: Dave Hansen <dave.hansen@...ux.intel.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "x86@...nel.org"
	<x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Michael Kelley
	<mikelley@...rosoft.com>, Kuppuswamy Sathyanarayanan
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, Kai Huang
	<kai.huang@...el.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] x86/tdx: Fix crash on kexec

> From: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Sent: Saturday, June 29, 2024 7:04 AM
> 
> On Sat, Jun 29, 2024 at 03:59:33PM +0200, Borislav Petkov wrote:
> > On Sat, Jun 29, 2024 at 04:06:20PM +0300, Kirill A. Shutemov wrote:
> > > The function tdx_enc_status_changed() was modified to handle vmalloc()
> > > mappings. It now utilizes slow_virt_to_phys() to determine the physical
> > > address of the page by walking page tables and looking for the physical
> > > address in the page table entry.
> > >
> > > However, this adjustment conflicted with the enabling of kexec. The
> > > function tdx_kexec_finish() clears the page table entry before calling
> > > tdx_enc_status_changed(), causing a BUG_ON() error in
> > > slow_virt_to_phys().
> > >
> > > To address this issue, tdx_enc_status_change() should use __pa() to
> > > obtain physical addresses whenever possible. The virt_addr_valid() check
> > > will handle such cases, while any other scenarios, including vmalloc()
> > > mappings, will resort to slow_virt_to_phys().
> > >
> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > > Fixes: e1b8ac3aae58 ("x86/tdx: Support vmalloc() for
> tdx_enc_status_changed()")
> >
> > I'm going to zap this one from x86/urgent and give you guys ample time to
> >  test
> > thus stuff better and longer.
> >
> > Also, what is this e1b8ac3aae58 fixing and why is it urgent?
> 
> Daxuan, how urgent is this fix for you?
> 
> --
>   Kiryl Shutsemau / Kirill A. Shutemov

Hi Kirill, Boris,
IMO e1b8ac3aae58  is not urgent and can go through the normal merge window.
It would be great to add e1b8ac3aae58 to the branch x86/tdx.

Thanks,
Dexuan