linux-kernel - Re: [PATCH 02/26] x86/tdx: Extend the cc_platform

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Date:   Wed, 15 Dec 2021 15:37:32 -0800
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, knsathya@...nel.org, pbonzini@...hat.com,
        sdeep@...are.com, seanjc@...gle.com, tony.luck@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/26] x86/tdx: Extend the cc_platform_has() API to
 support TDX guests

On Thu, Dec 16, 2021 at 02:35:17AM +0300, Kirill A. Shutemov wrote:
> On Wed, Dec 15, 2021 at 03:19:04PM -0800, Josh Poimboeuf wrote:
> > On Tue, Dec 14, 2021 at 06:02:40PM +0300, Kirill A. Shutemov wrote:
> > > --- a/arch/x86/kernel/Makefile
> > > +++ b/arch/x86/kernel/Makefile
> > > @@ -22,6 +22,7 @@ CFLAGS_REMOVE_early_printk.o = -pg
> > >  CFLAGS_REMOVE_head64.o = -pg
> > >  CFLAGS_REMOVE_sev.o = -pg
> > >  CFLAGS_REMOVE_cc_platform.o = -pg
> > > +CFLAGS_REMOVE_tdx.o = -pg
> > >  endif
> > >  
> > >  KASAN_SANITIZE_head$(BITS).o				:= n
> > > @@ -31,6 +32,7 @@ KASAN_SANITIZE_stacktrace.o				:= n
> > >  KASAN_SANITIZE_paravirt.o				:= n
> > >  KASAN_SANITIZE_sev.o					:= n
> > >  KASAN_SANITIZE_cc_platform.o				:= n
> > > +KASAN_SANITIZE_tdx.o					:= n
> > >  
> > >  # With some compiler versions the generated code results in boot hangs, caused
> > >  # by several compilation units. To be safe, disable all instrumentation.
> > > @@ -50,6 +52,7 @@ KCOV_INSTRUMENT		:= n
> > >  
> > >  CFLAGS_head$(BITS).o	+= -fno-stack-protector
> > >  CFLAGS_cc_platform.o	+= -fno-stack-protector
> > > +CFLAGS_tdx.o		+= -fno-stack-protector
> > >  
> > >  CFLAGS_irq.o := -I $(srctree)/$(src)/../include/asm/trace
> > 
> > Don't these Makefile changes belong in patch 1, which adds tdx.c?
> 
> Removing of the instrumentation is required because is_tdx_guest() is
> called from cc_platform_has().
> 
> Commit message tries to communicate this:
> 
> 	Since is_tdx_guest() function (through cc_platform_has() API) is used in
> 	the early boot code, disable the instrumentation flags and function
> 	tracer. This is similar to AMD SEV and cc_platform.c.

Ah, that's what I get for skimming the patch description.

-- 
Josh