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From: Paolo Bonzini <pbonzini@redhat.com>
To: Chia-I Wu <olvaffe@gmail.com>, kvm@vger.kernel.org
Cc: wanpengli@tencent.com, joro@8bytes.org,
	dri-devel@lists.freedesktop.org, gurchetansingh@chromium.org,
	kraxel@redhat.com, vkuznets@redhat.com, jmattson@google.com
Subject: Re: [RFC PATCH 0/3] KVM: x86: honor guest memory type
Date: Thu, 13 Feb 2020 22:41:22 +0100	[thread overview]
Message-ID: <8fdb85ea-6441-9519-ae35-eaf91ffe8741@redhat.com> (raw)
In-Reply-To: <20200213213036.207625-1-olvaffe@gmail.com>

On 13/02/20 22:30, Chia-I Wu wrote:
> Hi,
> 
> Host GPU drivers like to give userspace WC mapping.  When the userspace makes
> the mapping available to a guest, it also tells the guest to create a WC
> mapping.  However, even when the guest kernel picks the correct memory type,
> it gets ignored because of VMX_EPT_IPAT_BIT on Intel.
> 
> This series adds a new flag to KVM_SET_USER_MEMORY_REGION, which tells the
> host kernel to honor the guest memory type for the memslot.  An alternative
> fix is for KVM to unconditionally honor the guest memory type (unless it is
> MMIO, to avoid MCEs on Intel).  I believe the alternative fix is how things
> are on ARM, and probably also how things are on AMD.
> 
> I am new to KVM and HW virtualization technologies.  This series is meant as
> an RFC.
> 

When we tried to do this in the past, we got machine checks everywhere
unfortunately due to the same address being mapped with different memory
types.  Unfortunately I cannot find the entry anymore in bugzilla, but
this was not fixed as far as I know.

Paolo

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WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Chia-I Wu <olvaffe@gmail.com>, kvm@vger.kernel.org
Cc: vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
	joro@8bytes.org, gurchetansingh@chromium.org, kraxel@redhat.com,
	dri-devel@lists.freedesktop.org
Subject: Re: [RFC PATCH 0/3] KVM: x86: honor guest memory type
Date: Thu, 13 Feb 2020 22:41:22 +0100	[thread overview]
Message-ID: <8fdb85ea-6441-9519-ae35-eaf91ffe8741@redhat.com> (raw)
In-Reply-To: <20200213213036.207625-1-olvaffe@gmail.com>

On 13/02/20 22:30, Chia-I Wu wrote:
> Hi,
> 
> Host GPU drivers like to give userspace WC mapping.  When the userspace makes
> the mapping available to a guest, it also tells the guest to create a WC
> mapping.  However, even when the guest kernel picks the correct memory type,
> it gets ignored because of VMX_EPT_IPAT_BIT on Intel.
> 
> This series adds a new flag to KVM_SET_USER_MEMORY_REGION, which tells the
> host kernel to honor the guest memory type for the memslot.  An alternative
> fix is for KVM to unconditionally honor the guest memory type (unless it is
> MMIO, to avoid MCEs on Intel).  I believe the alternative fix is how things
> are on ARM, and probably also how things are on AMD.
> 
> I am new to KVM and HW virtualization technologies.  This series is meant as
> an RFC.
> 

When we tried to do this in the past, we got machine checks everywhere
unfortunately due to the same address being mapped with different memory
types.  Unfortunately I cannot find the entry anymore in bugzilla, but
this was not fixed as far as I know.

Paolo


  parent reply	other threads:[~2020-02-13 21:41 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13 21:30 [RFC PATCH 0/3] KVM: x86: honor guest memory type Chia-I Wu
2020-02-13 21:30 ` Chia-I Wu
2020-02-13 21:30 ` [RFC PATCH 1/3] KVM: vmx: rewrite the comment in vmx_get_mt_mask Chia-I Wu
2020-02-13 21:30   ` Chia-I Wu
2020-02-14  9:36   ` Paolo Bonzini
2020-02-14  9:36     ` Paolo Bonzini
2020-02-13 21:30 ` [RFC PATCH 2/3] RFC: KVM: add KVM_MEM_DMA Chia-I Wu
2020-02-13 21:30   ` Chia-I Wu
2020-02-13 21:30 ` [RFC PATCH 3/3] RFC: KVM: x86: support KVM_CAP_DMA_MEM Chia-I Wu
2020-02-13 21:30   ` Chia-I Wu
2020-02-13 21:41 ` Paolo Bonzini [this message]
2020-02-13 21:41   ` [RFC PATCH 0/3] KVM: x86: honor guest memory type Paolo Bonzini
2020-02-13 22:18   ` Chia-I Wu
2020-02-13 22:18     ` Chia-I Wu
2020-02-14 10:26     ` Paolo Bonzini
2020-02-14 10:26       ` Paolo Bonzini
2020-02-14 19:52       ` Sean Christopherson
2020-02-14 19:52         ` Sean Christopherson
2020-02-14 21:47         ` Chia-I Wu
2020-02-14 21:47           ` Chia-I Wu
2020-02-14 21:56           ` Jim Mattson
2020-02-14 21:56             ` Jim Mattson
2020-02-14 22:03             ` Sean Christopherson
2020-02-14 22:03               ` Sean Christopherson
2020-02-18 16:28               ` Paolo Bonzini
2020-02-18 16:28                 ` Paolo Bonzini
2020-02-18 22:58                 ` Sean Christopherson
2020-02-18 22:58                   ` Sean Christopherson
2020-02-19  9:52                 ` Tian, Kevin
2020-02-19  9:52                   ` Tian, Kevin
2020-02-19 19:36                   ` Chia-I Wu
2020-02-19 19:36                     ` Chia-I Wu
2020-02-20  2:04                     ` Tian, Kevin
2020-02-20  2:04                       ` Tian, Kevin
2020-02-20  2:38                       ` Tian, Kevin
2020-02-20  2:38                         ` Tian, Kevin
2020-02-20 22:23                         ` Chia-I Wu
2020-02-20 22:23                           ` Chia-I Wu
2020-02-21  0:23                           ` Tian, Kevin
2020-02-21  0:23                             ` Tian, Kevin
2020-02-21  4:45                             ` Chia-I Wu
2020-02-21  4:51                               ` Chia-I Wu
2020-02-21  4:51                                 ` Chia-I Wu
2020-02-21  5:39                                 ` Tian, Kevin
2020-02-21  5:39                                   ` Tian, Kevin
2020-02-21 15:59                                   ` Sean Christopherson
2020-02-21 15:59                                     ` Sean Christopherson
2020-02-21 18:21                                     ` Chia-I Wu
2020-02-21 18:21                                       ` Chia-I Wu
2020-02-25  1:29                                       ` Tian, Kevin
2020-02-25  1:29                                         ` Tian, Kevin
2020-02-14 21:15       ` Chia-I Wu
2020-02-14 21:15         ` Chia-I Wu
2020-02-19 10:00         ` Tian, Kevin
2020-02-19 10:00           ` Tian, Kevin
2020-02-19 19:18           ` Chia-I Wu
2020-02-19 19:18             ` Chia-I Wu
2020-02-20  2:13             ` Tian, Kevin
2020-02-20  2:13               ` Tian, Kevin
2020-02-20 23:02               ` Chia-I Wu
2020-02-20 23:02                 ` Chia-I Wu
2020-02-24 10:57               ` Gerd Hoffmann
2020-02-24 10:57                 ` Gerd Hoffmann

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