linux-kernel - Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native

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Message-ID: <aCiNPuwTtrepFc3x@gmail.com>
Date: Sat, 17 May 2025 15:21:02 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Xin Li <xin@...or.com>
Cc: linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
	linux-acpi@...r.kernel.org, tglx@...utronix.de, bp@...en8.de,
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
	peterz@...radead.org, jgross@...e.com, boris.ostrovsky@...cle.com,
	rafael@...nel.org, lenb@...nel.org
Subject: Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to
 native_wrmsrq()


* Xin Li <xin@...or.com> wrote:

> 
> >>> On 5/15/2025 10:54 AM, Xin Li wrote:
> >>> On 5/15/2025 8:27 AM, Ingo Molnar wrote:
> >>>> 
> >>>> * Xin Li (Intel) <xin@...or.com> wrote:
> >>>> 
> >>>>> Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
> >>>>> conversions when a u64 MSR value is splitted into two u32.
> >>>>> 
> >>>> 
> >>>> BTW., at this point we should probably just replace
> >>>> sev_es_wr_ghcb_msr() calls with direct calls to:
> >>>> 
> >>>>     native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);
> >>>> 
> >>>> as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().
> >>>> 
> >>> 
> >>> I thought about it, however it looks to me that current code prefers not
> >>> to spread MSR_AMD64_SEV_ES_GHCB in 17 callsites.  And anyway it's a
> >>> __always_inline function.
> >>> 
> >>> But as you have asked, I will make the change unless someone objects.
> >> 
> >> Hi Ingo,
> >> 
> >> I took a further look and found that we can't simply replace
> >> sev_es_wr_ghcb_msr() with native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...).
> >> 
> >> There are two sev_es_wr_ghcb_msr() definitions.  One is defined in
> >> arch/x86/boot/compressed/sev.h and it references boot_wrmsr() defined in
> >> arch/x86/boot/msr.h to do MSR write.
> > 
> > Ah, indeed, it's also a startup code wrapper, which wrmsrq() doesn't
> > have at the moment. Fair enough.
> 
> So you want me to drop this patch then?

No, patch #3 is fine as-is in its -v1 form, I was wrong.

Thanks,

	Ingo