netdev - Re: [PATCH v4 10/15] x86/xen/msr: Remove calling native_{read,write}_msr{,_safe}() in pmu_msr

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Message-ID: <aBSCk5phiMYO_B6T@gmail.com>
Date: Fri, 2 May 2025 10:30:11 +0200
From: Ingo Molnar <mingo@...nel.org>
To: "Xin Li (Intel)" <xin@...or.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
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Subject: Re: [PATCH v4 10/15] x86/xen/msr: Remove calling
 native_{read,write}_msr{,_safe}() in pmu_msr_{read,write}()


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

> hpa found that pmu_msr_write() is actually a completely pointless
> function [1]: all it does is shuffle some arguments, then calls
> pmu_msr_chk_emulated() and if it returns true AND the emulated flag
> is clear then does *exactly the same thing* that the calling code
> would have done if pmu_msr_write() itself had returned true.  And
> pmu_msr_read() does the equivalent stupidity.
> 
> Remove the calls to native_{read,write}_msr{,_safe}() within
> pmu_msr_{read,write}().  Instead reuse the existing calling code
> that decides whether to call native_{read,write}_msr{,_safe}() based
> on the return value from pmu_msr_{read,write}().  Consequently,
> eliminate the need to pass an error pointer to pmu_msr_{read,write}().
> 
> While at it, refactor pmu_msr_write() to take the MSR value as a u64
> argument, replacing the current dual u32 arguments, because the dual
> u32 arguments were only used to call native_write_msr{,_safe}(), which
> has now been removed.
> 
> [1]: https://lore.kernel.org/lkml/0ec48b84-d158-47c6-b14c-3563fd14bcc4@zytor.com/
> 
> Suggested-by: H. Peter Anvin (Intel) <hpa@...or.com>
> Sign-off-by: Xin Li (Intel) <xin@...or.com>

'Sign-off-by' is not a proper SOB tag, I've changed it to Signed-off-by.

Thanks,

	Ingo