linux-kernel - Re: [PATCH] x86/tlb: Flush global mappings when KAISER is disabled

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Date:   Thu, 25 Mar 2021 11:52:34 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, Hugh Dickins <hughd@...gle.com>
Cc:     Babu Moger <babu.moger@....com>, Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        kvm list <kvm@...r.kernel.org>, Joerg Roedel <joro@...tes.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Makarand Sonare <makarandsonare@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH] x86/tlb: Flush global mappings when KAISER is disabled

On 25/03/21 11:29, Borislav Petkov wrote:
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index f5ca15622dc9..2bfa4deb8cae 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -245,12 +245,15 @@ static inline void __native_flush_tlb_single(unsigned long addr)
>   	 * ASID.  But, userspace flushes are probably much more
>   	 * important performance-wise.
>   	 *
> -	 * Make sure to do only a single invpcid when KAISER is
> -	 * disabled and we have only a single ASID.
> +	 * In the KAISER disabled case, do an INVLPG to make sure
> +	 * the mapping is flushed in case it is a global one.
>   	 */
> -	if (kaiser_enabled)
> +	if (kaiser_enabled) {
>   		invpcid_flush_one(X86_CR3_PCID_ASID_USER, addr);
> -	invpcid_flush_one(X86_CR3_PCID_ASID_KERN, addr);
> +		invpcid_flush_one(X86_CR3_PCID_ASID_KERN, addr);
> +	} else {
> +		asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
> +	}
>   }
>   
>   static inline void __flush_tlb_all(void)
> 

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>