linux-kernel - Re: [RFC PATCH V6 03/14] x86/sev: Add AMD sev-snp enlightened guest support on hyperv

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Date:   Tue, 16 May 2023 11:40:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, seanjc@...gle.com, pbonzini@...hat.com,
        jgross@...e.com, tiala@...rosoft.com, kirill@...temov.name,
        jiangshan.ljs@...group.com, ashish.kalra@....com,
        srutherford@...gle.com, akpm@...ux-foundation.org,
        anshuman.khandual@....com, pawan.kumar.gupta@...ux.intel.com,
        adrian.hunter@...el.com, daniel.sneddon@...ux.intel.com,
        alexander.shishkin@...ux.intel.com, sandipan.das@....com,
        ray.huang@....com, brijesh.singh@....com, michael.roth@....com,
        thomas.lendacky@....com, venu.busireddy@...cle.com,
        sterritt@...gle.com, tony.luck@...el.com, samitolvanen@...gle.com,
        fenghua.yu@...el.com, pangupta@....com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH V6 03/14] x86/sev: Add AMD sev-snp enlightened guest
 support on hyperv

On Mon, May 15, 2023 at 12:59:05PM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <tiala@...rosoft.com>
> 
> Enable #HV exception to handle interrupt requests from hypervisor.
> 
> Co-developed-by: Lendacky Thomas <thomas.lendacky@....com>
> Co-developed-by: Kalra Ashish <ashish.kalra@....com>
> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> ---
> Change since RFC V5:
>        * Merge patch "x86/sev: Fix interrupt exit code paths from
>         #HV exception" with this commit.
> 
> Change since RFC V3:
>        * Check NMI event when irq is disabled.
>        * Remove redundant variable
> ---
>  arch/x86/include/asm/idtentry.h    |  12 +-
>  arch/x86/include/asm/mem_encrypt.h |   2 +
>  arch/x86/include/uapi/asm/svm.h    |   4 +
>  arch/x86/kernel/sev.c              | 349 ++++++++++++++++++++++++-----
>  arch/x86/kernel/traps.c            |   2 +
>  5 files changed, 310 insertions(+), 59 deletions(-)
> 
> diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
> index b0f3501b2767..867073ccf1d1 100644
> --- a/arch/x86/include/asm/idtentry.h
> +++ b/arch/x86/include/asm/idtentry.h
> @@ -13,6 +13,12 @@
>  
>  #include <asm/irq_stack.h>
>  
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> +noinstr void irqentry_exit_hv_cond(struct pt_regs *regs, irqentry_state_t state);
> +#else
> +#define irqentry_exit_hv_cond(regs, state)	irqentry_exit(regs, state)
> +#endif
> +
>  /**
>   * DECLARE_IDTENTRY - Declare functions for simple IDT entry points
>   *		      No error code pushed by hardware
> @@ -201,7 +207,7 @@ __visible noinstr void func(struct pt_regs *regs,			\
>  	kvm_set_cpu_l1tf_flush_l1d();					\
>  	run_irq_on_irqstack_cond(__##func, regs, vector);		\
>  	instrumentation_end();						\
> -	irqentry_exit(regs, state);					\
> +	irqentry_exit_hv_cond(regs, state);				\
>  }									\
>  									\
>  static noinline void __##func(struct pt_regs *regs, u32 vector)
> @@ -241,7 +247,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
>  	kvm_set_cpu_l1tf_flush_l1d();					\
>  	run_sysvec_on_irqstack_cond(__##func, regs);			\
>  	instrumentation_end();						\
> -	irqentry_exit(regs, state);					\
> +	irqentry_exit_hv_cond(regs, state);				\
>  }									\
>  									\
>  static noinline void __##func(struct pt_regs *regs)
> @@ -270,7 +276,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
>  	__##func (regs);						\
>  	__irq_exit_raw();						\
>  	instrumentation_end();						\
> -	irqentry_exit(regs, state);					\
> +	irqentry_exit_hv_cond(regs, state);				\
>  }									\
>  									\
>  static __always_inline void __##func(struct pt_regs *regs)

WTF is this supposed to do and why is this the right way to achieve the
desired result?

Your changelog gives me 0 clues -- guess how much I then care about your
patches?