From: Xiao Guangrong <guangrong.xiao@gmail.com>
To: Haozhong Zhang <haozhong.zhang@intel.com>,
kvm@vger.kernel.org, x86@kernel.org
Cc: linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
rkrcmar@redhat.com, Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
Dan Williams <dan.j.williams@intel.com>,
ivan.d.cuevas.escareno@intel.com, karthik.kumar@intel.com,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@suse.de>,
Mikulas Patocka <mpatocka@redhat.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH 0/3] KVM: MMU: fix kvm_is_mmio_pfn()
Date: Tue, 31 Oct 2017 16:12:29 +0800 [thread overview]
Message-ID: <6828fd44-f883-3f90-3e7c-1246300f4c41@gmail.com> (raw)
In-Reply-To: <20171027022524.22589-1-haozhong.zhang@intel.com>
On 10/27/2017 10:25 AM, Haozhong Zhang wrote:
> [I just copy the commit message from patch 3]
>
> By default, KVM treats a reserved page as for MMIO purpose, and maps
> it to guest with UC memory type. However, some reserved pages are not
> for MMIO, such as pages of DAX device (e.g., /dev/daxX.Y). Mapping
> them with UC memory type will harm the performance. In order to
> exclude those cases, we check the host cache mode in addition and only
> treat UC/UC- pages as MMIO.
>
I am afraid that is not only a performance issue but also a architecture
bug - it could trigger MCE as there is alias memory mapping (a page mapped
as both WB and UC).
It may hurt mdev device as well as the device memory may be both mapped
at host and VM.
prev parent reply other threads:[~2017-10-31 8:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-27 2:25 Haozhong Zhang
2017-10-27 2:25 ` [PATCH 1/3] x86/mm: expose track_pfn_insert() Haozhong Zhang
2017-10-27 2:25 ` [PATCH 2/3] KVM: add converters between pfn_t and kvm_pfn_t Haozhong Zhang
2017-10-27 2:25 ` [PATCH 3/3] KVM: MMU: consider host cache type in MMIO pfn check Haozhong Zhang
2017-10-27 8:40 ` Ingo Molnar
2017-10-31 7:35 ` Haozhong Zhang
2017-10-31 8:12 ` Xiao Guangrong [this message]
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