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Message-ID: <5dc0263aa963534bb049b61adbfb18dec3f65f00.camel@intel.com>
Date: Wed, 14 Dec 2022 11:43:14 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Yamahata, Isaku" <isaku.yamahata@...el.com>
CC: "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
"pbonzini@...hat.com" <pbonzini@...hat.com>,
"Shahar, Sagi" <sagis@...gle.com>,
"Aktas, Erdem" <erdemaktas@...gle.com>,
"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
"dmatlack@...gle.com" <dmatlack@...gle.com>,
"Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v10 105/108] KVM: TDX: Add methods to ignore accesses to
CPU state
On Sat, 2022-10-29 at 23:23 -0700, isaku.yamahata@...el.com wrote:
> +static u8 vt_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> +{
> + if (is_td_vcpu(vcpu)) {
> + if (is_mmio)
> + return MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT;
> + returnĀ MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT;
> + }
> +
> + return vmx_get_mt_mask(vcpu, gfn, is_mmio);
> +}
So you are returning WB for _ALL_ guest memory, including shared. Wouldn't this
break MTRR handling for shared memory? For instance, IIUC we can still support
assigning a device to a TDX guest while the VT-d doesn't support coherent
memory, in which case guest's MTRR/PAT are honored. I think this should also
apply to TDX guest's shared memory?
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