On June 16, 2022 4:52 AM, Dionna Glaze wrote: > > > > > > > With the help of fw_cfg, we can know the size of > > > QemuFwCfgItemKernelSize/ > > > QemuFwCfgItemInitrdSize/QemuFwCfgItemKernelSetupSize. > > > > That'll only work with direct kernel boot, when some boot loader is in > > your boot workflow this will not work. > > Indeed, the TDX startup library does things very differently from how we'd > handle this for SEV-SNP. There are already 2 ranges of memory prevalidated > in SEC that have to be specially skipped over in PEI. > I tried the lazy accept changes from edk2-staging with SEV-SNP changes to > prevalidate only the PEI installed memory > https://github.com/AMDESE/ovmf/pull/4 and I just could not manage to get > the guest to boot. It'd crash in the QemuTryBootKernel part of BDS. > > Tom Lendacky's suggestion for SEV-SNP is to pre-accept all memory under > 4GB to make all that complexity go away. Only this approach worked in my > own testing. With the MMIO hole it's just validating 3GB of memory. Accepting all memory under 4GB will make the things much simpler. In this way I think the accept-on-demand maybe not needed. A question: is there some performance impact when accepting all memory under 4GB?
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