From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:52174 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753568AbeDYKkh (ORCPT ); Wed, 25 Apr 2018 06:40:37 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vitaly Kuznetsov , Thomas Gleixner , David Zhang , Stephen Hemminger , Haiyang Zhang , "Michael Kelley (EOSG)" , Andy Lutomirski , devel@linuxdriverproject.org, "K. Y. Srinivasan" , Aditya Bhandari , Sasha Levin Subject: [PATCH 4.14 087/183] x86/hyperv: Stop suppressing X86_FEATURE_PCID Date: Wed, 25 Apr 2018 12:35:07 +0200 Message-Id: <20180425103245.991958948@linuxfoundation.org> In-Reply-To: <20180425103242.532713678@linuxfoundation.org> References: <20180425103242.532713678@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vitaly Kuznetsov [ Upstream commit 617ab45c9a8900e64a78b43696c02598b8cad68b ] When hypercall-based TLB flush was enabled for Hyper-V guests PCID feature was deliberately suppressed as a precaution: back then PCID was never exposed to Hyper-V guests and it wasn't clear what will happen if some day it becomes available. The day came and PCID/INVPCID features are already exposed on certain Hyper-V hosts. >>>From TLFS (as of 5.0b) it is unclear how TLB flush hypercalls combine with PCID. In particular the usage of PCID is per-cpu based: the same mm gets different CR3 values on different CPUs. If the hypercall does exact matching this will fail. However, this is not the case. David Zhang explains: "In practice, the AddressSpace argument is ignored on any VM that supports PCIDs. Architecturally, the AddressSpace argument must match the CR3 with PCID bits stripped out (i.e., the low 12 bits of AddressSpace should be 0 in long mode). The flush hypercalls flush all PCIDs for the specified AddressSpace." With this, PCID can be enabled. Signed-off-by: Vitaly Kuznetsov Signed-off-by: Thomas Gleixner Cc: David Zhang Cc: Stephen Hemminger Cc: Haiyang Zhang Cc: "Michael Kelley (EOSG)" Cc: Andy Lutomirski Cc: devel@linuxdriverproject.org Cc: "K. Y. Srinivasan" Cc: Aditya Bhandari Link: https://lkml.kernel.org/r/20180124103629.29980-1-vkuznets@redhat.com Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/hyperv/mmu.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/arch/x86/hyperv/mmu.c +++ b/arch/x86/hyperv/mmu.c @@ -137,7 +137,12 @@ static void hyperv_flush_tlb_others(cons } if (info->mm) { + /* + * AddressSpace argument must match the CR3 with PCID bits + * stripped out. + */ flush->address_space = virt_to_phys(info->mm->pgd); + flush->address_space &= CR3_ADDR_MASK; flush->flags = 0; } else { flush->address_space = 0; @@ -219,7 +224,12 @@ static void hyperv_flush_tlb_others_ex(c } if (info->mm) { + /* + * AddressSpace argument must match the CR3 with PCID bits + * stripped out. + */ flush->address_space = virt_to_phys(info->mm->pgd); + flush->address_space &= CR3_ADDR_MASK; flush->flags = 0; } else { flush->address_space = 0; @@ -278,8 +288,6 @@ void hyperv_setup_mmu_ops(void) if (!(ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED)) return; - setup_clear_cpu_cap(X86_FEATURE_PCID); - if (!(ms_hyperv.hints & HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED)) { pr_info("Using hypercall for remote TLB flush\n"); pv_mmu_ops.flush_tlb_others = hyperv_flush_tlb_others;