On Sun, Jan 29, 2023 at 04:37:24AM +0000, Michael Kelley (LINUX) wrote: > From: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx> Sent: Monday, January 23, 2023 8:51 AM > > > > Hyper-V can expose the SEV-SNP feature to guests, and manages the > > system-wide RMP (Reverse Map) table. The SNP implementation in the > > kernel needs access to the rmptable for tracking pages and deciding > > when/how to issue rmpupdate/psmash. When running as a Hyper-V guest > > with SNP support, an rmptable is allocated by the kernel during boot for > > this purpose. Keep the table in sync with issued rmpupdate/psmash > > instructions. > > > > The logic for how to update the rmptable comes from "AMD64 Architecture > > Programmer’s Manual, Volume 3" which describes the psmash and rmpupdate > > instructions. To ensure correctness of the SNP host code, the most > > important fields are "assigned" and "page size". > > > > Signed-off-by: Jeremi Piotrowski <jpiotrowski@xxxxxxxxxxxxxxxxxxx> > > --- > > arch/x86/kernel/sev.c | 59 +++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 59 insertions(+) > > > > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c > > index 95404c7e5150..edec1ccb80b1 100644 > > --- a/arch/x86/kernel/sev.c > > +++ b/arch/x86/kernel/sev.c > > @@ -26,6 +26,7 @@ > > #include <linux/iommu.h> > > #include <linux/amd-iommu.h> > > > > +#include <asm/mshyperv.h> > > The code in sev.c should be generic and appropriate for use with any > hypervisor. As such, I think we want to avoid sev.c having a dependency > on Hyper-V specific code, such as the <asm/mshyperv.h> include file > and the ms_hyperv.nested_features variable as used below. > > Instead, create a boolean static variable in the sev.c module along with > a wrapper function to set it. The logic that tests hv_no_rmp_table() > should test this static variable instead, which would default to "false". > Hypervisor-specific initialization code can call the wrapper function > to set the variable to "true" based on whatever logic is appropriate for > the hypervisor. This approach reverses the dependency and hopefully > is usable by other hypervisors that want to offer nested SNP support. > ok, this makes sense. I've added a call to the wrapper to the init_mem_mapping callback added before so that it is enabled together with allocating the rmptable.
