linux-kernel - Re: [PATCH v5 13/13] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ddd4ba8a-27cf-4174-a578-b28961bdf1a5@rivosinc.com>
Date: Thu, 24 Apr 2025 14:37:11 +0200
From: Clément Léger <cleger@...osinc.com>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Anup Patel <anup@...infault.org>,
 Atish Patra <atishp@...shpatra.org>, Shuah Khan <shuah@...nel.org>,
 Jonathan Corbet <corbet@....net>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
 linux-kselftest@...r.kernel.org, Samuel Holland <samuel.holland@...ive.com>,
 Deepak Gupta <debug@...osinc.com>
Subject: Re: [PATCH v5 13/13] RISC-V: KVM: add support for
 SBI_FWFT_MISALIGNED_DELEG



On 24/04/2025 13:34, Andrew Jones wrote:
> On Thu, Apr 17, 2025 at 02:20:00PM +0200, Clément Léger wrote:
>> SBI_FWFT_MISALIGNED_DELEG needs hedeleg to be modified to delegate
>> misaligned load/store exceptions. Save and restore it during CPU
>> load/put.
>>
>> Signed-off-by: Clément Léger <cleger@...osinc.com>
>> Reviewed-by: Deepak Gupta <debug@...osinc.com>
>> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
>> ---
>>  arch/riscv/kvm/vcpu.c          |  3 +++
>>  arch/riscv/kvm/vcpu_sbi_fwft.c | 36 ++++++++++++++++++++++++++++++++++
>>  2 files changed, 39 insertions(+)
>>
>> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
>> index 542747e2c7f5..d98e379945c3 100644
>> --- a/arch/riscv/kvm/vcpu.c
>> +++ b/arch/riscv/kvm/vcpu.c
>> @@ -646,6 +646,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>>  {
>>  	void *nsh;
>>  	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
>> +	struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;
>>  
>>  	vcpu->cpu = -1;
>>  
>> @@ -671,6 +672,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>>  		csr->vstval = nacl_csr_read(nsh, CSR_VSTVAL);
>>  		csr->hvip = nacl_csr_read(nsh, CSR_HVIP);
>>  		csr->vsatp = nacl_csr_read(nsh, CSR_VSATP);
>> +		cfg->hedeleg = nacl_csr_read(nsh, CSR_HEDELEG);
>>  	} else {
>>  		csr->vsstatus = csr_read(CSR_VSSTATUS);
>>  		csr->vsie = csr_read(CSR_VSIE);
>> @@ -681,6 +683,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>>  		csr->vstval = csr_read(CSR_VSTVAL);
>>  		csr->hvip = csr_read(CSR_HVIP);
>>  		csr->vsatp = csr_read(CSR_VSATP);
>> +		cfg->hedeleg = csr_read(CSR_HEDELEG);
>>  	}
>>  }
>>  
>> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
>> index b0f66c7bf010..237edaefa267 100644
>> --- a/arch/riscv/kvm/vcpu_sbi_fwft.c
>> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
>> @@ -14,6 +14,8 @@
>>  #include <asm/kvm_vcpu_sbi.h>
>>  #include <asm/kvm_vcpu_sbi_fwft.h>
>>  
>> +#define MIS_DELEG (BIT_ULL(EXC_LOAD_MISALIGNED) | BIT_ULL(EXC_STORE_MISALIGNED))
>> +
>>  struct kvm_sbi_fwft_feature {
>>  	/**
>>  	 * @id: Feature ID
>> @@ -68,7 +70,41 @@ static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
>>  	return false;
>>  }
>>  
>> +static bool kvm_sbi_fwft_misaligned_delegation_supported(struct kvm_vcpu *vcpu)
>> +{
>> +	return misaligned_traps_can_delegate();
>> +}
>> +
>> +static long kvm_sbi_fwft_set_misaligned_delegation(struct kvm_vcpu *vcpu,
>> +					struct kvm_sbi_fwft_config *conf,
>> +					unsigned long value)
>> +{
>> +	if (value == 1)
>> +		csr_set(CSR_HEDELEG, MIS_DELEG);
>> +	else if (value == 0)
>> +		csr_clear(CSR_HEDELEG, MIS_DELEG);
>> +	else
>> +		return SBI_ERR_INVALID_PARAM;
>> +
>> +	return SBI_SUCCESS;
>> +}
>> +
>> +static long kvm_sbi_fwft_get_misaligned_delegation(struct kvm_vcpu *vcpu,
>> +					struct kvm_sbi_fwft_config *conf,
>> +					unsigned long *value)
>> +{
>> +	*value = (csr_read(CSR_HEDELEG) & MIS_DELEG) != 0;
> 
> This should be
> 
>   (csr_read(CSR_HEDELEG) & MIS_DELEG) == MIS_DELEG;

Hum yeah indeed, I didn't thought that someone would ony delegate load
or stores.

I'll fix that,

Thanks,

Clément

> 
>> +
>> +	return SBI_SUCCESS;
>> +}
>> +
>>  static const struct kvm_sbi_fwft_feature features[] = {
>> +	{
>> +		.id = SBI_FWFT_MISALIGNED_EXC_DELEG,
>> +		.supported = kvm_sbi_fwft_misaligned_delegation_supported,
>> +		.set = kvm_sbi_fwft_set_misaligned_delegation,
>> +		.get = kvm_sbi_fwft_get_misaligned_delegation,
>> +	},
>>  };
>>  
>>  static struct kvm_sbi_fwft_config *
>> -- 
>> 2.49.0
>>
> 
> Thanks,
> drew