linux-kernel - Re: [PATCH v6 07/16] KVM: MMU: Introduce level info in PFERR code

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Message-ID: <20231121100241.GE1109547@ls.amr.corp.intel.com>
Date:   Tue, 21 Nov 2023 02:02:41 -0800
From:   Isaku Yamahata <isaku.yamahata@...ux.intel.com>
To:     Binbin Wu <binbin.wu@...ux.intel.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        hang.yuan@...el.com, tina.zhang@...el.com,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v6 07/16] KVM: MMU: Introduce level info in PFERR code

On Mon, Nov 20, 2023 at 06:54:07PM +0800,
Binbin Wu <binbin.wu@...ux.intel.com> wrote:

> 
> 
> On 11/7/2023 11:00 PM, isaku.yamahata@...el.com wrote:
> > From: Xiaoyao Li <xiaoyao.li@...el.com>
> > 
> > For TDX, EPT violation can happen when TDG.MEM.PAGE.ACCEPT.
> > And TDG.MEM.PAGE.ACCEPT contains the desired accept page level of TD guest.
> > 
> > 1. KVM can map it with 4KB page while TD guest wants to accept 2MB page.
> > 
> >    TD geust will get TDX_PAGE_SIZE_MISMATCH and it should try to accept
> s/geust/guest
> 
> >    4KB size.
> > 
> > 2. KVM can map it with 2MB page while TD guest wants to accept 4KB page.
> > 
> >    KVM needs to honor it because
> >    a) there is no way to tell guest KVM maps it as 2MB size. And
> >    b) guest accepts it in 4KB size since guest knows some other 4KB page
> >       in the same 2MB range will be used as shared page.
> > 
> > For case 2, it need to pass desired page level to MMU's
> > page_fault_handler. Use bit 29:31 of kvm PF error code for this purpose.
> 
> The level info is needed not only for case 2, KVM also needs the info so
> that
> it can map a 2MB page when TD guest wants to accept a 2MB page.

"MMU's page_fault_handler" = KVM MMU page fault handler, isn't it?
I'll replace it with KVM MMU page fault handler for clarity.
-- 
Isaku Yamahata <isaku.yamahata@...ux.intel.com>