linux-kernel - Re: [PATCH V3 1/2] x86/tdx: Route safe halt execution via tdx_safe

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Message-ID: <CAGtprH_4Z15UdPDDCYg=pnroS41fX7c7VzK_ziPMsk=UgQYfgw@mail.gmail.com>
Date: Tue, 11 Feb 2025 16:22:59 -0800
From: Vishal Annapurve <vannapurve@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, x86@...nel.org, 
	linux-kernel@...r.kernel.org, pbonzini@...hat.com, seanjc@...gle.com, 
	erdemaktas@...gle.com, ackerleytng@...gle.com, jxgao@...gle.com, 
	sagis@...gle.com, oupton@...gle.com, pgonda@...gle.com, kirill@...temov.name, 
	dave.hansen@...ux.intel.com, linux-coco@...ts.linux.dev, 
	chao.p.peng@...ux.intel.com, isaku.yamahata@...il.com, stable@...r.kernel.org
Subject: Re: [PATCH V3 1/2] x86/tdx: Route safe halt execution via tdx_safe_halt()

On Tue, Feb 11, 2025 at 3:46 PM Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 2/11/25 00:32, Kirill A. Shutemov wrote:
> >> If CONFIG_PARAVIRT_XXL is disabled, "sti;hlt" sequences can still get
> >> executed from TDX VMs via paths like:
> >>         acpi_safe_halt() =>
> >>         raw_safe_halt()  =>
> >>         arch_safe_halt() =>
> >>      native_safe_halt()
> >> There is a long term plan to fix these paths by carving out
> >> irq.safe_halt() outside paravirt framework.
> > I don't think it is acceptable to keep !PARAVIRT_XXL (read no-Xen) config
> > broken.
>
> Oh, I thought it took PARAVIRT_XXL=y to even trigger this issue. Was I
> just confused?

Original issue with unsafe "sti;hlt" execution for TDX VMs doesn't
need PARAVIRT_XXL to be enabled in theory. Any caller just needs to
reach native*halt() to trigger the issue.