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Message-ID: <887a77acc9bf96f7c7bea519ab7ebdd27fb67985.camel@intel.com>
Date: Fri, 25 Nov 2022 00:13:48 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Zhao, Yan Y" <yan.y.zhao@...el.com>,
"Yamahata, Isaku" <isaku.yamahata@...el.com>
CC: "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Christopherson,, Sean" <seanjc@...gle.com>,
"Shahar, Sagi" <sagis@...gle.com>,
"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
"Aktas, Erdem" <erdemaktas@...gle.com>,
"dmatlack@...gle.com" <dmatlack@...gle.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"pbonzini@...hat.com" <pbonzini@...hat.com>
Subject: Re: [PATCH v10 035/108] KVM: x86/mmu: Track shadow MMIO value on a
per-VM basis
On Tue, 2022-11-22 at 10:10 +0800, Yan Zhao wrote:
> Also make enable_mmio_caching to be a per-VM value?
> As if the shadow_mmio_value is 0, mmio_caching needs to be disabled.
If I recall correctly, Sean said we can disable TDX guests if mmio_caching is
disabled (we also will need to change to allow enable_mmio_caching to still be
true when mmio_value is 0).
SEV_ES has similar logic:
void __init sev_hardware_setup(void)
{
...
/*
* SEV-ES requires MMIO caching as KVM doesn't have access to the guest
* instruction stream, i.e. can't emulate in response to a #NPF and
* instead relies on #NPF(RSVD) being reflected into the guest as #VC
* (the guest can then do a #VMGEXIT to request MMIO emulation).
*/
if (!enable_mmio_caching)
goto out;
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