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X-CSE-ConnectionGUID: 2nCK+34xR0WghbQ4hWn5qg== X-CSE-MsgGUID: WWRPlPubR/e+2gBJiIk/zg== X-IronPort-AV: E=McAfee;i="6800,10657,11586"; a="67049063" X-IronPort-AV: E=Sophos;i="6.19,250,1754982000"; d="scan'208";a="67049063" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Oct 2025 08:03:46 -0700 X-CSE-ConnectionGUID: m4kbs3LhRwaias4kXu0j8g== X-CSE-MsgGUID: n2jvHvr4RNme4UzLO79rvg== X-ExtLoop1: 1 Received: from tfalcon-desk.amr.corp.intel.com (HELO [10.125.108.251]) ([10.125.108.251]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Oct 2025 08:03:45 -0700 Message-ID: Date: Thu, 23 Oct 2025 08:03:44 -0700 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 05/21] x86/cea: Export API for per-CPU exception stacks for KVM To: "Xin Li (Intel)" , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org Cc: pbonzini@redhat.com, seanjc@google.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, chao.gao@intel.com, hch@infradead.org References: <20251014010950.1568389-1-xin@zytor.com> <20251014010950.1568389-6-xin@zytor.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit A couple of nits: The subject here isn't super helpful. This is doing a *LOT* more than just exporting something. In a perfect world, you'd probably even do the refactoring first and export in a separate patch. On 10/13/25 18:09, Xin Li (Intel) wrote: > Convert the __this_cpu_ist_{top,bottom}_va() macros into proper functions, > and export __this_cpu_ist_top_va() to allow KVM to retrieve the top of the > per-CPU exception stack. The key thing this does is create a data structure and move away from open-coded size calculations to using the compiler for it. The macro=>function conversion is barely worth mentioning, IMNHO. > FRED introduced new fields in the host-state area of the VMCS for stack > levels 1->3 (HOST_IA32_FRED_RSP[123]), each respectively corresponding to > per-CPU exception stacks for #DB, NMI and #DF. KVM must populate these > fields each time a vCPU is loaded onto a CPU. > > To simplify access to the exception stacks in struct cea_exception_stacks, > a union is used to create an array alias, enabling array-style indexing of > the stack entries. Super nit here, but please use imperative voice for stuff like this. "To simplify access to" => "Simplify access to" and/or "a union is used" => "use a union" > diff --git a/arch/x86/include/asm/cpu_entry_area.h b/arch/x86/include/asm/cpu_entry_area.h > index d0f884c28178..58cd71144e5e 100644 > --- a/arch/x86/include/asm/cpu_entry_area.h > +++ b/arch/x86/include/asm/cpu_entry_area.h > @@ -16,6 +16,19 @@ > #define VC_EXCEPTION_STKSZ 0 > #endif > > +/* > + * The exception stack ordering in [cea_]exception_stacks > + */ > +enum exception_stack_ordering { > + ESTACK_DF, > + ESTACK_NMI, > + ESTACK_DB, > + ESTACK_MCE, > + ESTACK_VC, > + ESTACK_VC2, > + N_EXCEPTION_STACKS > +}; This creates some new duplicated logic. There's already a list in the same order in ESTACKS_MEMBERS() of all the stacks. Ideally, everyone would move over to the enum and wouldn't need to use the ESTACKS_MEMBERS() route. What's preventing that?