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Subject: Re: [PATCH RESEND v4 0/9] Enable Sub-page Write Protection Support
To:     Yang Weijiang <weijiang.yang@intel.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com
Cc:     mst@redhat.com, rkrcmar@redhat.com, jmattson@google.com,
        yu.c.zhang@intel.com, alazar@bitdefender.com
References: <20190814070403.6588-1-weijiang.yang@intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
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Date:   Wed, 14 Aug 2019 14:36:30 +0200
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On 14/08/19 09:03, Yang Weijiang wrote:
> EPT-Based Sub-Page write Protection(SPP)is a HW capability which allows
> Virtual Machine Monitor(VMM) to specify write-permission for guest
> physical memory at a sub-page(128 byte) granularity. When this
> capability is enabled, the CPU enforces write-access check for sub-pages
> within a 4KB page.
> 
> The feature is targeted to provide fine-grained memory protection for
> usages such as device virtualization, memory check-point and VM
> introspection etc.
> 
> SPP is active when the "sub-page write protection" (bit 23) is 1 in
> Secondary VM-Execution Controls. The feature is backed with a Sub-Page
> Permission Table(SPPT), SPPT is referenced via a 64-bit control field
> called Sub-Page Permission Table Pointer (SPPTP) which contains a
> 4K-aligned physical address.
> 
> Right now, only 4KB physical pages are supported for SPP. To enable SPP
> for certain physical page, we need to first make the physical page
> write-protected, then set bit 61 of the corresponding EPT leaf entry. 
> While HW walks EPT, if bit 61 is set, it traverses SPPT with the guset
> physical address to find out the sub-page permissions at the leaf entry.
> If the corresponding bit is set, write to sub-page is permitted,
> otherwise, SPP induced EPT violation is generated.

Still no testcases?

Paolo