linux-kernel - Re: [PATCH v5 09/10] RISC-V: KVM: Allow Smnpm and Ssnpm extensions for guests

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Message-ID: <CAAhSdy3FTjVUDBJtbsFwj6+DWjrQh3nWwvsm_1edDUO9SkXB2A@mail.gmail.com>
Date: Sun, 20 Oct 2024 21:56:58 +0530
From: Anup Patel <anup@...infault.org>
To: Samuel Holland <samuel.holland@...ive.com>
Cc: Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org, 
	Catalin Marinas <catalin.marinas@....com>, Atish Patra <atishp@...shpatra.org>, 
	linux-kselftest@...r.kernel.org, Rob Herring <robh+dt@...nel.org>, 
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, Shuah Khan <shuah@...nel.org>, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jonathan Corbet <corbet@....net>, kvm-riscv@...ts.infradead.org, 
	Conor Dooley <conor@...nel.org>, kasan-dev@...glegroups.com, linux-doc@...r.kernel.org, 
	Evgenii Stepanov <eugenis@...gle.com>, Charlie Jenkins <charlie@...osinc.com>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [PATCH v5 09/10] RISC-V: KVM: Allow Smnpm and Ssnpm extensions
 for guests

On Thu, Oct 17, 2024 at 1:58 AM Samuel Holland
<samuel.holland@...ive.com> wrote:
>
> The interface for controlling pointer masking in VS-mode is henvcfg.PMM,
> which is part of the Ssnpm extension, even though pointer masking in
> HS-mode is provided by the Smnpm extension. As a result, emulating Smnpm
> in the guest requires (only) Ssnpm on the host.
>
> The guest configures Smnpm through the SBI Firmware Features extension,
> which KVM does not yet implement, so currently the ISA extension has no
> visible effect on the guest, and thus it cannot be disabled. Ssnpm is
> configured using the senvcfg CSR within the guest, so that extension
> cannot be hidden from the guest without intercepting writes to the CSR.
>
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>

LGTM.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

> ---
>
> Changes in v5:
>  - Do not allow Smnpm to be disabled, as suggested by Anup
>
> Changes in v2:
>  - New patch for v2
>
>  arch/riscv/include/uapi/asm/kvm.h | 2 ++
>  arch/riscv/kvm/vcpu_onereg.c      | 4 ++++
>  2 files changed, 6 insertions(+)
>
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index e97db3296456..4f24201376b1 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -175,6 +175,8 @@ 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_SMNPM,
> +       KVM_RISCV_ISA_EXT_SSNPM,
>         KVM_RISCV_ISA_EXT_MAX,
>  };
>
> diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
> index b319c4c13c54..5b68490ad9b7 100644
> --- a/arch/riscv/kvm/vcpu_onereg.c
> +++ b/arch/riscv/kvm/vcpu_onereg.c
> @@ -34,9 +34,11 @@ static const unsigned long kvm_isa_ext_arr[] = {
>         [KVM_RISCV_ISA_EXT_M] = RISCV_ISA_EXT_m,
>         [KVM_RISCV_ISA_EXT_V] = RISCV_ISA_EXT_v,
>         /* Multi letter extensions (alphabetically sorted) */
> +       [KVM_RISCV_ISA_EXT_SMNPM] = RISCV_ISA_EXT_SSNPM,
>         KVM_ISA_EXT_ARR(SMSTATEEN),
>         KVM_ISA_EXT_ARR(SSAIA),
>         KVM_ISA_EXT_ARR(SSCOFPMF),
> +       KVM_ISA_EXT_ARR(SSNPM),
>         KVM_ISA_EXT_ARR(SSTC),
>         KVM_ISA_EXT_ARR(SVINVAL),
>         KVM_ISA_EXT_ARR(SVNAPOT),
> @@ -127,8 +129,10 @@ static bool kvm_riscv_vcpu_isa_disable_allowed(unsigned long ext)
>         case KVM_RISCV_ISA_EXT_C:
>         case KVM_RISCV_ISA_EXT_I:
>         case KVM_RISCV_ISA_EXT_M:
> +       case KVM_RISCV_ISA_EXT_SMNPM:
>         /* There is not architectural config bit to disable sscofpmf completely */
>         case KVM_RISCV_ISA_EXT_SSCOFPMF:
> +       case KVM_RISCV_ISA_EXT_SSNPM:
>         case KVM_RISCV_ISA_EXT_SSTC:
>         case KVM_RISCV_ISA_EXT_SVINVAL:
>         case KVM_RISCV_ISA_EXT_SVNAPOT:
> --
> 2.45.1
>