Re: [PATCH RFC v2 3/3] riscv: KVM: Add Svukte extension support for Guest/VM

Hi Anup,

Thank you for the suggestion.

I’m not entirely sure if I fully understand it, but I believe the
hypervisor should be able to disable the Svukte extension.

Inside the switch-case of kvm_riscv_vcpu_isa_disable_allowed(),
the default case breaks and returns true.

So that means when the KVM_RISCV_ISA_EXT_SVUKTE passed into
kvm_riscv_vcpu_isa_disable_allowed() it will return true.

If I've misunderstood, please let me know.

Best regards,
Max Hsu

On Fri, Oct 25, 2024 at 3:17 AM Anup Patel [off-list ref] wrote:

On Fri, Sep 27, 2024 at 7:12 PM Max Hsu [off-list ref] wrote:

quoted

Add KVM ISA extension ONE_REG interface to allow VMM tools to
detect and enable Svukte extension for Guest/VM.

Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Max Hsu <redacted>
---
 arch/riscv/include/uapi/asm/kvm.h | 1 +
 arch/riscv/kvm/vcpu_onereg.c      | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index e97db3296456e19f79ca02e4c4f70ae1b4abb48b..41b466b7ffaec421e8389d3f5b178580091a2c98 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h

@@ -175,6 +175,7 @@ enum KVM_RISCV_ISA_EXT_ID {
        KVM_RISCV_ISA_EXT_ZCF,
        KVM_RISCV_ISA_EXT_ZCMOP,
        KVM_RISCV_ISA_EXT_ZAWRS,
+       KVM_RISCV_ISA_EXT_SVUKTE,
        KVM_RISCV_ISA_EXT_MAX,
 };

diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index b319c4c13c54ce22d2a7552f4c9f256a0c50780e..67237d6e53882a9fcd2cf265aa1704f25cc4a701 100644
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c

@@ -41,6 +41,7 @@ static const unsigned long kvm_isa_ext_arr[] = {
        KVM_ISA_EXT_ARR(SVINVAL),
        KVM_ISA_EXT_ARR(SVNAPOT),
        KVM_ISA_EXT_ARR(SVPBMT),
+       KVM_ISA_EXT_ARR(SVUKTE),
        KVM_ISA_EXT_ARR(ZACAS),
        KVM_ISA_EXT_ARR(ZAWRS),
        KVM_ISA_EXT_ARR(ZBA),

The KVM_RISCV_ISA_EXT_SVUKTE should be added to the
switch-case in kvm_riscv_vcpu_isa_disable_allowed() because
hypervisor seems to have no way to disable Svukte for the Guest
when it's available on the Host.

Regards,
Anup