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Subject: Re: [PATCH v6 00/12] SVM cleanup and INVPCID feature support
To:     Borislav Petkov <bp@alien8.de>, Babu Moger <babu.moger@amd.com>,
        Hugh Dickins <hughd@google.com>
Cc:     Jim Mattson <jmattson@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        kvm list <kvm@vger.kernel.org>, Joerg Roedel <joro@8bytes.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Makarand Sonare <makarandsonare@google.com>,
        Sean Christopherson <seanjc@google.com>
References: <78cc2dc7-a2ee-35ac-dd47-8f3f8b62f261@redhat.com>
 <d7c6211b-05d3-ec3f-111a-f69f09201681@amd.com>
 <20210311200755.GE5829@zn.tnic> <20210311203206.GF5829@zn.tnic>
 <2ca37e61-08db-3e47-f2b9-8a7de60757e6@amd.com>
 <20210311214013.GH5829@zn.tnic>
 <d3e9e091-0fc8-1e11-ab99-9c8be086f1dc@amd.com>
 <4a72f780-3797-229e-a938-6dc5b14bec8d@amd.com>
 <20210311235215.GI5829@zn.tnic>
 <ed590709-65c8-ca2f-013f-d2c63d5ee0b7@amd.com>
 <20210324212139.GN5010@zn.tnic>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <feabccbb-8e0f-83b0-64a7-b5e1988c4559@redhat.com>
Date:   Wed, 24 Mar 2021 22:59:29 +0100
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On 24/03/21 22:21, Borislav Petkov wrote:
>  	if (kaiser_enabled)
>   		invpcid_flush_one(X86_CR3_PCID_ASID_USER, addr);
> +	else
> +		asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
> +
>   	invpcid_flush_one(X86_CR3_PCID_ASID_KERN, addr);
>   }

I think the kernel ASID flush can also be moved under the "if"?

> and the reason why it does, IMHO, is because on AMD, kaiser_enabled is
> false because AMD is not affected by Meltdown, which means, there's no
> user/kernel pagetables split.
> 
> And that also means, you have global TLB entries which means that if you
> look at that __native_flush_tlb_single() function, it needs to flush
> global TLB entries on CPUs with X86_FEATURE_INVPCID_SINGLE by doing an
> INVLPG in the kaiser_enabled=0 case. Errgo, the above hunk.

Makes sense.

Paolo