linux-kernel - Re: [RFC PATCH 1/7] riscv: kvm: add support for FWFT SBI extension

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Message-ID: <99d3eabc-0289-4ace-90a8-ad02dbffd6d2@rivosinc.com>
Date: Tue, 30 Apr 2024 09:26:24 +0200
From: Clément Léger <cleger@...osinc.com>
To: Deepak Gupta <debug@...osinc.com>
Cc: Conor Dooley <conor@...nel.org>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Anup Patel <anup@...infault.org>, Atish Patra <atishp@...shpatra.org>,
 linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 kvm-riscv@...ts.infradead.org, Ved Shanbhogue <ved@...osinc.com>
Subject: Re: [RFC PATCH 1/7] riscv: kvm: add support for FWFT SBI extension



On 27/04/2024 01:44, Deepak Gupta wrote:
> On Thu, Apr 18, 2024 at 04:26:40PM +0200, Clément Léger wrote:
>> Add support for FWFT extension in KVM
>>
>> Signed-off-by: Clément Léger <cleger@...osinc.com>
>> ---
>> arch/riscv/include/asm/kvm_host.h          |   5 +
>> arch/riscv/include/asm/kvm_vcpu_sbi.h      |   1 +
>> arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h |  37 ++++++
>> arch/riscv/include/uapi/asm/kvm.h          |   1 +
>> arch/riscv/kvm/Makefile                    |   1 +
>> arch/riscv/kvm/vcpu.c                      |   5 +
>> arch/riscv/kvm/vcpu_sbi.c                  |   4 +
>> arch/riscv/kvm/vcpu_sbi_fwft.c             | 136 +++++++++++++++++++++
>> 8 files changed, 190 insertions(+)
>> create mode 100644 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
>> create mode 100644 arch/riscv/kvm/vcpu_sbi_fwft.c
>>
>> diff --git a/arch/riscv/include/asm/kvm_host.h
>> b/arch/riscv/include/asm/kvm_host.h
>> index 484d04a92fa6..be60aaa07f57 100644
>> --- a/arch/riscv/include/asm/kvm_host.h
>> +++ b/arch/riscv/include/asm/kvm_host.h
>> @@ -19,6 +19,7 @@
>> #include <asm/kvm_vcpu_fp.h>
>> #include <asm/kvm_vcpu_insn.h>
>> #include <asm/kvm_vcpu_sbi.h>
>> +#include <asm/kvm_vcpu_sbi_fwft.h>
>> #include <asm/kvm_vcpu_timer.h>
>> #include <asm/kvm_vcpu_pmu.h>
>>
>> @@ -169,6 +170,7 @@ struct kvm_vcpu_csr {
>> struct kvm_vcpu_config {
>>     u64 henvcfg;
>>     u64 hstateen0;
>> +    u64 hedeleg;
>> };
>>
>> struct kvm_vcpu_smstateen_csr {
>> @@ -261,6 +263,9 @@ struct kvm_vcpu_arch {
>>     /* Performance monitoring context */
>>     struct kvm_pmu pmu_context;
>>
>> +    /* Firmware feature SBI extension context */
>> +    struct kvm_sbi_fwft fwft_context;
>> +
>>     /* 'static' configurations which are set only once */
>>     struct kvm_vcpu_config cfg;
>>
>> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> index b96705258cf9..3a33bbacc233 100644
>> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> @@ -86,6 +86,7 @@ extern const struct kvm_vcpu_sbi_extension
>> vcpu_sbi_ext_srst;
>> extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
>> extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_dbcn;
>> extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta;
>> +extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft;
>> extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
>> extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
>>
>> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
>> b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
>> new file mode 100644
>> index 000000000000..7dc1b80c7e6c
>> --- /dev/null
>> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
>> @@ -0,0 +1,37 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (c) 2023 Rivos Inc
>> + *
>> + * Authors:
>> + *     Atish Patra <atishp@...osinc.com>
> 
> nit: probably need to fix Copyright year and Authors here :-)
> Same in all new files being introduced.
> 
>> + */
>> +
>> +#ifndef __KVM_VCPU_RISCV_FWFT_H
>> +#define __KVM_VCPU_RISCV_FWFT_H
>> +
>> +#include <asm/sbi.h>
>> +
>> +#define KVM_SBI_FWFT_FEATURE_COUNT    1
>> +
>> +static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu,
>> +                enum sbi_fwft_feature_t feature,
>> +                unsigned long value, unsigned long flags)
>> +{
>> +    struct kvm_sbi_fwft_config *conf = kvm_sbi_fwft_get_config(vcpu,
>> +                                   feature);
>> +    if (!conf)
>> +        return SBI_ERR_DENIED;
> 
> Curious,
> Why denied and not something like NOT_SUPPORTED NOT_AVAILABLE here?

Hey Deepak,

So indeed, the return value is not totally correct since the spec states
that we return  EDENIED if feature is reserved or is platform-specific
and unimplemented. But in that case it dos not distinguish between
defined features and reserved one. I'll add a check for that.

Thanks,

Clément

> 
>> +
>> +    if ((flags & ~SBI_FWFT_SET_FLAG_LOCK) != 0)
>> +        return SBI_ERR_INVALID_PARAM;
>> +
>> +    if (conf->flags & SBI_FWFT_SET_FLAG_LOCK)
>> +        return SBI_ERR_DENIED;
>> +
>> +    conf->flags = flags;
>> +
>> +    return conf->feature->set(vcpu, conf, value);
>> +}
>> +