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

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Message-ID: <poxeykijyqrz5hxrey46s6hh2qd6byirbevwuwec2gtbfq266c@npegk7sn3ot7>
Date: Sat, 29 Jun 2024 17:04:08 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Borislav Petkov <bp@...en8.de>, Dexuan Cui <decui@...rosoft.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 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-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/tdx: Fix crash on kexec

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