Messages in this thread | | | Date | Wed, 27 Mar 2024 21:49:14 +0800 | Subject | Re: [PATCH v19 058/130] KVM: x86/mmu: Add a private pointer to struct kvm_mmu_page | From | Binbin Wu <> |
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On 3/15/2024 9:09 AM, Isaku Yamahata wrote: > Here is the updated one. Renamed dummy -> mirroed. > > When KVM resolves the KVM page fault, it walks the page tables. To reuse > the existing KVM MMU code and mitigate the heavy cost of directly walking > the private page table, allocate one more page to copy the mirrored page
Here "copy" is a bit confusing for me. The mirrored page table is maintained by KVM, not copied from anywhere.
> table for the KVM MMU code to directly walk. Resolve the KVM page fault > with the existing code, and do additional operations necessary for the > private page table. To distinguish such cases, the existing KVM page table > is called a shared page table (i.e., not associated with a private page > table), and the page table with a private page table is called a mirrored > page table. The relationship is depicted below. > > > KVM page fault | > | | > V | > -------------+---------- | > | | | > V V | > shared GPA private GPA | > | | | > V V | > shared PT root mirrored PT root | private PT root > | | | | > V V | V > shared PT mirrored PT ----propagate----> private PT > | | | | > | \-----------------+------\ | > | | | | > V | V V > shared guest page | private guest page > | > non-encrypted memory | encrypted memory > | > PT: Page table > Shared PT: visible to KVM, and the CPU uses it for shared mappings. > Private PT: the CPU uses it, but it is invisible to KVM. TDX module > updates this table to map private guest pages. > Mirrored PT: It is visible to KVM, but the CPU doesn't use it. KVM uses it > to propagate PT change to the actual private PT. >
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