On Fri, Dec 13, 2024 at 5:03 PM Max Hsu <max.hsu@xxxxxxxxxx> wrote: > > RISC-V privileged spec will be added with Svukte extension [1] > > Svukte introduce senvcfg.UKTE and hstatus.HUKTE bitfield. > which makes user-mode access to supervisor memory raise page faults > in constant time, mitigating attacks that attempt to discover the > supervisor software's address-space layout. > > In the Linux kernel, since the hstatus.HU bit is not enabled, > the following patches only enable the use of senvcfg.UKTE. > > For Guest environments, because a Guest OS (not limited to Linux) > may hold mappings from GVA to GPA, the Guest OS should decide > whether to enable the protection provided by the Svukte extension. > > Since the Guest OS may utilize the Svukte extension simply by setting > the senvcfg.UKTE without any trap to host. In the view of VMM, the > Svukte extension should be always presented. Therefore adding an > extra entry in kvm_riscv_vcpu_isa_disable_allowed(). > > If the Guest environment wants to change senvcfg.UKTE, KVM already > provides the senvcfg CSR swap support via > kvm_riscv_vcpu_swap_in_(host|guest)_state. > Thus, there is no concern about the Guest OS affecting the Host OS. > > The following patches add > - dt-binding of Svukte ISA string > - CSR bit definition, ISA detection, senvcfg.UKTE enablement in kernel > - KVM ISA support for Svukte extension > > Changes in v4: > - rebase on riscv/for-next > - add kvm_riscv_vcpu_isa_disable_allowed() entry addressed by Anup > and Andrew from v2/v3 patches. > - update the cover letter for the detailed reason > - update the commit message on dt-binding for the Svukte ISA string > - Link to v3: https://lore.kernel.org/all/20241120-dev-maxh-svukte-v3-v3-0-1e533d41ae15@xxxxxxxxxx/ > > Changes in v3: > - rebase on riscv/for-next > - fixed typo in the dt-binding for the Svukte ISA string > - updated the commit message for KVM support for the Svukte extension > - Link to v2: https://lore.kernel.org/all/20240927-dev-maxh-svukte-rebase-2-v2-0-9afe57c33aee@xxxxxxxxxx/ > > Changes in v2: > - rebase on riscv/for-next (riscv-for-linus-6.12-mw1) > - modify the description of dt-binding on Svukte ISA string > - Link to v1: https://lore.kernel.org/all/20240920-dev-maxh-svukte-rebase-v1-0-7864a88a62bd@xxxxxxxxxx/ > > Link: https://github.com/riscv/riscv-isa-manual/pull/1564 [1] > > Signed-off-by: Max Hsu <max.hsu@xxxxxxxxxx> > > --- > Max Hsu (3): > dt-bindings: riscv: Add Svukte entry > riscv: Add Svukte extension support > riscv: KVM: Add Svukte extension support for Guest/VM Overall, this series looks good to me. Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx> As-per Linux RISC-V patch acceptance policy, we will have to wait until the spec is frozen. Regards, Anup > > Documentation/devicetree/bindings/riscv/extensions.yaml | 9 +++++++++ > arch/riscv/include/asm/csr.h | 2 ++ > arch/riscv/include/asm/hwcap.h | 1 + > arch/riscv/include/uapi/asm/kvm.h | 1 + > arch/riscv/kernel/cpufeature.c | 5 +++++ > arch/riscv/kvm/vcpu_onereg.c | 2 ++ > 6 files changed, 20 insertions(+) > --- > base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4 > change-id: 20241213-dev-maxh-svukte-v4-34101ec945e9 > > Best regards, > -- > Max Hsu <max.hsu@xxxxxxxxxx> >
