Messages in this thread | | | Subject | Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | From | Brijesh Singh <> | Date | Mon, 15 Nov 2021 12:58:54 -0600 |
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On 11/15/21 12:44 PM, Sean Christopherson wrote: > On Mon, Nov 15, 2021, Brijesh Singh wrote: >> >> On 11/12/21 2:37 PM, Sean Christopherson wrote: >>> This is the direction KVM TDX support is headed, though it's obviously still a WIP. >>> >> >> Just curious, in this approach, how do you propose handling the host >> kexec/kdump? If a kexec/kdump occurs while the VM is still active, the new >> kernel will encounter the #PF (RMP violation) because some pages are still >> marked 'private' in the RMP table. > > There are two basic options: a) eagerly purge the RMP or b) lazily fixup the RMP > on #PF. Either approach can be made to work. I'm not opposed to fixing up the RMP > on #PF in the kexec/kdump case, I'm opposed to blindly updating the RMP on _all_ > RMP #PFs, i.e. the kernel should modify the RMP if and only if it knows that doing > so is correct. E.g. a naive lazy-fixup solution would be to track which pages have > been sanitized and adjust the RMP on #PF to a page that hasn't yet been sanitized. >
Yap, I think option #a will require the current kernel to iterate through the entire memory and make it shared before booting the kexec kernel. It may bring another ask to track the guest private/shared on the host to minimize the iterations.
thanks
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