[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [RISC-V] Switch to H-mode
On Mon, 2023-01-23 at 22:32 +0000, Alistair Francis wrote: > On Mon, 2023-01-23 at 18:56 +0200, Oleksii wrote: > > Hi Alistair and community, > > > > I am working on RISC-V support upstream for Xen based on your and > > Bobby > > patches. > > > > Adding the RISC-V support I realized that Xen is ran in S-mode. > > Output > > of OpenSBI: > > ... > > Domain0 Next Mode : S-mode > > ... > > So the first my question is shouldn't it be in H-mode? > > There is no H-mode in RISC-V. > > When the Hypervisor extension exists the standard S-mode > automatically > becomes HS-mode. The two names can be used interchangeably (although > the spec calls it HS-mode). > > In this way Linux (with or without KVM support) and Xen all boot in > the > same mode and can choose to use virtulisation if desired. > > > > > If I am right than it looks like we have to do a patch to OpenSBI > > to > > add support of H-mode as it is not supported now: > > [1] > > https://github.com/riscv-software-src/opensbi/blob/master/lib/sbi/sbi_domain.c#L380 > > [2] > > https://github.com/riscv-software-src/opensbi/blob/master/include/sbi/riscv_encoding.h#L110 > > Please correct me if I am wrong. > > > > The other option I see is to switch to H-mode in U-boot as I > > understand > > the classical boot flow is: > > OpenSBI -> U-boot -> Xen -> Domain{0,...} > > If it is at all possible since U-boot will be in S mode after > > OpenSBI. > > S-mode is where you want to be. That's what Xen should start in. > Thanks for clarification. ~ Oleksii > Alistair > > > > > Thanks in advance. > > > > ~ Oleksii >
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