linux-kernel - Re: [PATCH] KVM: x86/mmu: Embed direct bits into gpa for KVM_PRE_FAULT

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <02ee52259c7c6b342d9c6ddf303fbf27004bf4ef.camel@intel.com>
Date: Thu, 12 Jun 2025 18:40:07 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>
CC: "Huang, Kai" <kai.huang@...el.com>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Chatre,
 Reinette" <reinette.chatre@...el.com>, "Hunter, Adrian"
	<adrian.hunter@...el.com>, "tony.lindgren@...ux.intel.com"
	<tony.lindgren@...ux.intel.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86/mmu: Embed direct bits into gpa for
 KVM_PRE_FAULT_MEMORY

On Thu, 2025-06-12 at 20:20 +0800, Yan Zhao wrote:
> What about passing is is_private instead?  
> 
> static inline bool kvm_is_mirror_fault(struct kvm *kvm, bool is_private)
> {
>  	return kvm_has_mirrored_tdp(kvm) && is_private;
> }
> 
> tdp_mmu_get_root_for_fault() and kvm_tdp_mmu_gpa_is_mapped() can pass in
> faul->is_private or is_private directly, leaving the parsing of error_code &
> PFERR_PRIVATE_ACCESS only in kvm_mmu_do_page_fault().

General question about the existing code...

Why do we have the error code bits separated out into bools in struct
kvm_page_fault? It transitions between:
1. Native exit info (exit qualification, AMD error code, etc)
2. Synthetic error codes
3. struct kvm_page_fault bools *and* synthetic error code.

Why don't we go right to struct kvm_page_fault bools? Or just leave the
synthetic error code in struct kvm_page_fault and refer to it? Having both in
struct kvm_page_fault seems wrong, at least.