linux-kernel - Re: [PATCH v3 09/27] KVM: VMX: Do not use MAX_POSSIBLE_PASSTHROUGH

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20241126180253.GAZ0YNTdXH1UGeqsu6@fat_crate.local>
Date: Tue, 26 Nov 2024 19:02:53 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Xin Li (Intel)" <xin@...or.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, seanjc@...gle.com, pbonzini@...hat.com,
	corbet@....net, tglx@...utronix.de, mingo@...hat.com,
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
	luto@...nel.org, peterz@...radead.org, andrew.cooper3@...rix.com
Subject: Re: [PATCH v3 09/27] KVM: VMX: Do not use
 MAX_POSSIBLE_PASSTHROUGH_MSRS in array definition

On Mon, Sep 30, 2024 at 10:00:52PM -0700, Xin Li (Intel) wrote:
> No need to use MAX_POSSIBLE_PASSTHROUGH_MSRS in the definition of array
> vmx_possible_passthrough_msrs, as the macro name indicates the _possible_
> maximum size of passthrough MSRs.
> 
> Use ARRAY_SIZE instead of MAX_POSSIBLE_PASSTHROUGH_MSRS when the size of
> the array is needed and add a BUILD_BUG_ON to make sure the actual array
> size does not exceed the possible maximum size of passthrough MSRs.

This commit message needs to talk about the why - not the what. Latter should
be visible from the diff itself.

What you're not talking about is the sneaked increase of
MAX_POSSIBLE_PASSTHROUGH_MSRS to 64. Something you *should* mention because
the array is full and blablabla...

> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index e0d76d2460ef..e7409f8f28b1 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -356,7 +356,7 @@ struct vcpu_vmx {
>  	struct lbr_desc lbr_desc;
>  
>  	/* Save desired MSR intercept (read: pass-through) state */
> -#define MAX_POSSIBLE_PASSTHROUGH_MSRS	16
> +#define MAX_POSSIBLE_PASSTHROUGH_MSRS	64
						^^^

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette