[v5,12/22] RISC-V: KVM: Implement SBI PMU Snapshot feature

Message ID	20240403080452.1007601-13-atishp@rivosinc.com (mailing list archive)
State	New, archived
Headers	show Received: from mail-pl1-f179.google.com (mail-pl1-f179.google.com [209.85.214.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2029984D24 for <kvm@vger.kernel.org>; Wed, 3 Apr 2024 08:05:38 +0000 (UTC) From: Atish Patra <atishp@rivosinc.com> To: linux-kernel@vger.kernel.org Cc: Atish Patra <atishp@rivosinc.com>, Anup Patel <anup@brainfault.org>, Ajay Kaher <akaher@vmware.com>, Alexandre Ghiti <alexghiti@rivosinc.com>, Alexey Makhalov <amakhalov@vmware.com>, Andrew Jones <ajones@ventanamicro.com>, Conor Dooley <conor.dooley@microchip.com>, Juergen Gross <jgross@suse.com>, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-riscv@lists.infradead.org, Mark Rutland <mark.rutland@arm.com>, Palmer Dabbelt <palmer@dabbelt.com>, Paolo Bonzini <pbonzini@redhat.com>, Paul Walmsley <paul.walmsley@sifive.com>, Shuah Khan <shuah@kernel.org>, virtualization@lists.linux.dev, VMware PV-Drivers Reviewers <pv-drivers@vmware.com>, Will Deacon <will@kernel.org>, x86@kernel.org Subject: [PATCH v5 12/22] RISC-V: KVM: Implement SBI PMU Snapshot feature Date: Wed, 3 Apr 2024 01:04:41 -0700 Message-Id: <20240403080452.1007601-13-atishp@rivosinc.com> In-Reply-To: <20240403080452.1007601-1-atishp@rivosinc.com> References: <20240403080452.1007601-1-atishp@rivosinc.com> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit
Series	RISC-V SBI v2.0 PMU improvements and Perf sampling in KVM guest \| expand [v5,00/22] RISC-V SBI v2.0 PMU improvements and Perf sampling in KVM guest [v5,01/22] RISC-V: Fix the typo in Scountovf CSR name [v5,02/22] RISC-V: Add FIRMWARE_READ_HI definition [v5,03/22] drivers/perf: riscv: Read upper bits of a firmware counter [v5,04/22] drivers/perf: riscv: Use BIT macro for shifting operations [v5,05/22] RISC-V: Add SBI PMU snapshot definitions [v5,06/22] drivers/perf: riscv: Implement SBI PMU snapshot function [v5,07/22] drivers/perf: riscv: Fix counter mask iteration for RV32 [v5,08/22] RISC-V: KVM: Fix the initial sample period value [v5,09/22] RISC-V: KVM: Rename the SBI_STA_SHMEM_DISABLE to a generic name [v5,10/22] RISC-V: KVM: No need to update the counter value during reset [v5,11/22] RISC-V: KVM: No need to exit to the user space if perf event failed [v5,12/22] RISC-V: KVM: Implement SBI PMU Snapshot feature [v5,13/22] RISC-V: KVM: Add perf sampling support for guests [v5,14/22] RISC-V: KVM: Support 64 bit firmware counters on RV32 [v5,15/22] RISC-V: KVM: Improve firmware counter read function [v5,16/22] KVM: riscv: selftests: Move sbi definitions to its own header file [v5,17/22] KVM: riscv: selftests: Add helper functions for extension checks [v5,18/22] KVM: riscv: selftests: Add Sscofpmf to get-reg-list test [v5,19/22] KVM: riscv: selftests: Add SBI PMU extension definitions [v5,20/22] KVM: riscv: selftests: Add SBI PMU selftest [v5,21/22] KVM: riscv: selftests: Add a test for PMU snapshot functionality [v5,22/22] KVM: riscv: selftests: Add a test for counter overflow

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20240403080452.1007601-13-atishp@rivosinc.com (mailing list archive)

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New, archived

Headers

From: Atish Patra <atishp@rivosinc.com>
To: linux-kernel@vger.kernel.org
Cc: Atish Patra <atishp@rivosinc.com>,
	Anup Patel <anup@brainfault.org>,
	Ajay Kaher <akaher@vmware.com>,
	Alexandre Ghiti <alexghiti@rivosinc.com>,
	Alexey Makhalov <amakhalov@vmware.com>,
	Andrew Jones <ajones@ventanamicro.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	Juergen Gross <jgross@suse.com>,
	kvm-riscv@lists.infradead.org,
	kvm@vger.kernel.org,
	linux-kselftest@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	Mark Rutland <mark.rutland@arm.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Shuah Khan <shuah@kernel.org>,
	virtualization@lists.linux.dev,
	VMware PV-Drivers Reviewers <pv-drivers@vmware.com>,
	Will Deacon <will@kernel.org>,
	x86@kernel.org
Subject: [PATCH v5 12/22] RISC-V: KVM: Implement SBI PMU Snapshot feature
Date: Wed,  3 Apr 2024 01:04:41 -0700
Message-Id: <20240403080452.1007601-13-atishp@rivosinc.com>
In-Reply-To: <20240403080452.1007601-1-atishp@rivosinc.com>
References: <20240403080452.1007601-1-atishp@rivosinc.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Series

RISC-V SBI v2.0 PMU improvements and Perf sampling in KVM guest | expand

Commit Message

Atish Kumar Patra April 3, 2024, 8:04 a.m. UTC

PMU Snapshot function allows to minimize the number of traps when the
guest access configures/access the hpmcounters. If the snapshot feature
is enabled, the hypervisor updates the shared memory with counter
data and state of overflown counters. The guest can just read the
shared memory instead of trap & emulate done by the hypervisor.

This patch doesn't implement the counter overflow yet.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 arch/riscv/include/asm/kvm_vcpu_pmu.h |   7 ++
 arch/riscv/kvm/vcpu_pmu.c             | 121 +++++++++++++++++++++++++-
 arch/riscv/kvm/vcpu_sbi_pmu.c         |   3 +
 3 files changed, 130 insertions(+), 1 deletion(-)

Comments

Andrew Jones April 5, 2024, 11:23 a.m. UTC | #1

On Wed, Apr 03, 2024 at 01:04:41AM -0700, Atish Patra wrote:
> PMU Snapshot function allows to minimize the number of traps when the
> guest access configures/access the hpmcounters. If the snapshot feature
> is enabled, the hypervisor updates the shared memory with counter
> data and state of overflown counters. The guest can just read the
> shared memory instead of trap & emulate done by the hypervisor.
> 
> This patch doesn't implement the counter overflow yet.
> 
> Reviewed-by: Anup Patel <anup@brainfault.org>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
>  arch/riscv/include/asm/kvm_vcpu_pmu.h |   7 ++
>  arch/riscv/kvm/vcpu_pmu.c             | 121 +++++++++++++++++++++++++-
>  arch/riscv/kvm/vcpu_sbi_pmu.c         |   3 +
>  3 files changed, 130 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> index 395518a1664e..77a1fc4d203d 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
> @@ -50,6 +50,10 @@ struct kvm_pmu {
>  	bool init_done;
>  	/* Bit map of all the virtual counter used */
>  	DECLARE_BITMAP(pmc_in_use, RISCV_KVM_MAX_COUNTERS);
> +	/* The address of the counter snapshot area (guest physical address) */
> +	gpa_t snapshot_addr;
> +	/* The actual data of the snapshot */
> +	struct riscv_pmu_snapshot_data *sdata;
>  };
>  
>  #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu_context)
> @@ -85,6 +89,9 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
>  int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
>  				struct kvm_vcpu_sbi_return *retdata);
>  void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu);
> +int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
> +				      unsigned long saddr_high, unsigned long flags,
> +				      struct kvm_vcpu_sbi_return *retdata);
>  void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu);
>  void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
>  
> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
> index 2d9929bbc2c8..f706c688b338 100644
> --- a/arch/riscv/kvm/vcpu_pmu.c
> +++ b/arch/riscv/kvm/vcpu_pmu.c
> @@ -14,6 +14,7 @@
>  #include <asm/csr.h>
>  #include <asm/kvm_vcpu_sbi.h>
>  #include <asm/kvm_vcpu_pmu.h>
> +#include <asm/sbi.h>
>  #include <linux/bitops.h>
>  
>  #define kvm_pmu_num_counters(pmu) ((pmu)->num_hw_ctrs + (pmu)->num_fw_ctrs)
> @@ -311,6 +312,80 @@ int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
>  	return ret;
>  }
>  
> +static void kvm_pmu_clear_snapshot_area(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
> +
> +	if (kvpmu->sdata) {
> +		if (kvpmu->snapshot_addr != INVALID_GPA) {
> +			memset(kvpmu->sdata, 0, snapshot_area_size);
> +			kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr,
> +					     kvpmu->sdata, snapshot_area_size);
> +		} else {
> +			pr_warn("snapshot address invalid\n");
> +		}
> +		kfree(kvpmu->sdata);
> +		kvpmu->sdata = NULL;
> +	}
> +	kvpmu->snapshot_addr = INVALID_GPA;
> +}
> +
> +int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
> +				      unsigned long saddr_high, unsigned long flags,
> +				      struct kvm_vcpu_sbi_return *retdata)
> +{
> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
> +	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
> +	int sbiret = 0;
> +	gpa_t saddr;
> +	unsigned long hva;
> +	bool writable;
> +
> +	if (!kvpmu || flags) {
> +		sbiret = SBI_ERR_INVALID_PARAM;
> +		goto out;
> +	}
> +
> +	if (saddr_low == SBI_SHMEM_DISABLE && saddr_high == SBI_SHMEM_DISABLE) {
> +		kvm_pmu_clear_snapshot_area(vcpu);
> +		return 0;
> +	}
> +
> +	saddr = saddr_low;
> +
> +	if (saddr_high != 0) {
> +		if (IS_ENABLED(CONFIG_32BIT))
> +			saddr |= ((gpa_t)saddr << 32);

saddr |= ((gpa_t)saddr_high << 32)

> +		else
> +			sbiret = SBI_ERR_INVALID_ADDRESS;
> +		goto out;
> +	}
> +

Thanks,
drew

Atish Kumar Patra April 9, 2024, 12:33 a.m. UTC | #2

On 4/5/24 04:23, Andrew Jones wrote:
> On Wed, Apr 03, 2024 at 01:04:41AM -0700, Atish Patra wrote:
>> PMU Snapshot function allows to minimize the number of traps when the
>> guest access configures/access the hpmcounters. If the snapshot feature
>> is enabled, the hypervisor updates the shared memory with counter
>> data and state of overflown counters. The guest can just read the
>> shared memory instead of trap & emulate done by the hypervisor.
>>
>> This patch doesn't implement the counter overflow yet.
>>
>> Reviewed-by: Anup Patel <anup@brainfault.org>
>> Signed-off-by: Atish Patra <atishp@rivosinc.com>
>> ---
>>   arch/riscv/include/asm/kvm_vcpu_pmu.h |   7 ++
>>   arch/riscv/kvm/vcpu_pmu.c             | 121 +++++++++++++++++++++++++-
>>   arch/riscv/kvm/vcpu_sbi_pmu.c         |   3 +
>>   3 files changed, 130 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
>> index 395518a1664e..77a1fc4d203d 100644
>> --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h
>> +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
>> @@ -50,6 +50,10 @@ struct kvm_pmu {
>>   	bool init_done;
>>   	/* Bit map of all the virtual counter used */
>>   	DECLARE_BITMAP(pmc_in_use, RISCV_KVM_MAX_COUNTERS);
>> +	/* The address of the counter snapshot area (guest physical address) */
>> +	gpa_t snapshot_addr;
>> +	/* The actual data of the snapshot */
>> +	struct riscv_pmu_snapshot_data *sdata;
>>   };
>>   
>>   #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu_context)
>> @@ -85,6 +89,9 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
>>   int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
>>   				struct kvm_vcpu_sbi_return *retdata);
>>   void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu);
>> +int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
>> +				      unsigned long saddr_high, unsigned long flags,
>> +				      struct kvm_vcpu_sbi_return *retdata);
>>   void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu);
>>   void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
>>   
>> diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
>> index 2d9929bbc2c8..f706c688b338 100644
>> --- a/arch/riscv/kvm/vcpu_pmu.c
>> +++ b/arch/riscv/kvm/vcpu_pmu.c
>> @@ -14,6 +14,7 @@
>>   #include <asm/csr.h>
>>   #include <asm/kvm_vcpu_sbi.h>
>>   #include <asm/kvm_vcpu_pmu.h>
>> +#include <asm/sbi.h>
>>   #include <linux/bitops.h>
>>   
>>   #define kvm_pmu_num_counters(pmu) ((pmu)->num_hw_ctrs + (pmu)->num_fw_ctrs)
>> @@ -311,6 +312,80 @@ int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
>>   	return ret;
>>   }
>>   
>> +static void kvm_pmu_clear_snapshot_area(struct kvm_vcpu *vcpu)
>> +{
>> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
>> +	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
>> +
>> +	if (kvpmu->sdata) {
>> +		if (kvpmu->snapshot_addr != INVALID_GPA) {
>> +			memset(kvpmu->sdata, 0, snapshot_area_size);
>> +			kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr,
>> +					     kvpmu->sdata, snapshot_area_size);
>> +		} else {
>> +			pr_warn("snapshot address invalid\n");
>> +		}
>> +		kfree(kvpmu->sdata);
>> +		kvpmu->sdata = NULL;
>> +	}
>> +	kvpmu->snapshot_addr = INVALID_GPA;
>> +}
>> +
>> +int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
>> +				      unsigned long saddr_high, unsigned long flags,
>> +				      struct kvm_vcpu_sbi_return *retdata)
>> +{
>> +	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
>> +	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
>> +	int sbiret = 0;
>> +	gpa_t saddr;
>> +	unsigned long hva;
>> +	bool writable;
>> +
>> +	if (!kvpmu || flags) {
>> +		sbiret = SBI_ERR_INVALID_PARAM;
>> +		goto out;
>> +	}
>> +
>> +	if (saddr_low == SBI_SHMEM_DISABLE && saddr_high == SBI_SHMEM_DISABLE) {
>> +		kvm_pmu_clear_snapshot_area(vcpu);
>> +		return 0;
>> +	}
>> +
>> +	saddr = saddr_low;
>> +
>> +	if (saddr_high != 0) {
>> +		if (IS_ENABLED(CONFIG_32BIT))
>> +			saddr |= ((gpa_t)saddr << 32);
> 
> saddr |= ((gpa_t)saddr_high << 32)
> 

Oops. Thanks for catching it. Fixed.


>> +		else
>> +			sbiret = SBI_ERR_INVALID_ADDRESS;
>> +		goto out;
>> +	}
>> +
> 
> Thanks,
> drew

diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
index 395518a1664e..77a1fc4d203d 100644
--- a/arch/riscv/include/asm/kvm_vcpu_pmu.h
+++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
@@ -50,6 +50,10 @@  struct kvm_pmu {
 	bool init_done;
 	/* Bit map of all the virtual counter used */
 	DECLARE_BITMAP(pmc_in_use, RISCV_KVM_MAX_COUNTERS);
+	/* The address of the counter snapshot area (guest physical address) */
+	gpa_t snapshot_addr;
+	/* The actual data of the snapshot */
+	struct riscv_pmu_snapshot_data *sdata;
 };
 
 #define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu_context)
@@ -85,6 +89,9 @@  int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
 int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
 				struct kvm_vcpu_sbi_return *retdata);
 void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu);
+int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
+				      unsigned long saddr_high, unsigned long flags,
+				      struct kvm_vcpu_sbi_return *retdata);
 void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu);
 void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
 
diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 2d9929bbc2c8..f706c688b338 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -14,6 +14,7 @@ 
 #include <asm/csr.h>
 #include <asm/kvm_vcpu_sbi.h>
 #include <asm/kvm_vcpu_pmu.h>
+#include <asm/sbi.h>
 #include <linux/bitops.h>
 
 #define kvm_pmu_num_counters(pmu) ((pmu)->num_hw_ctrs + (pmu)->num_fw_ctrs)
@@ -311,6 +312,80 @@  int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
 	return ret;
 }
 
+static void kvm_pmu_clear_snapshot_area(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
+	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
+
+	if (kvpmu->sdata) {
+		if (kvpmu->snapshot_addr != INVALID_GPA) {
+			memset(kvpmu->sdata, 0, snapshot_area_size);
+			kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr,
+					     kvpmu->sdata, snapshot_area_size);
+		} else {
+			pr_warn("snapshot address invalid\n");
+		}
+		kfree(kvpmu->sdata);
+		kvpmu->sdata = NULL;
+	}
+	kvpmu->snapshot_addr = INVALID_GPA;
+}
+
+int kvm_riscv_vcpu_pmu_snapshot_set_shmem(struct kvm_vcpu *vcpu, unsigned long saddr_low,
+				      unsigned long saddr_high, unsigned long flags,
+				      struct kvm_vcpu_sbi_return *retdata)
+{
+	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
+	int snapshot_area_size = sizeof(struct riscv_pmu_snapshot_data);
+	int sbiret = 0;
+	gpa_t saddr;
+	unsigned long hva;
+	bool writable;
+
+	if (!kvpmu || flags) {
+		sbiret = SBI_ERR_INVALID_PARAM;
+		goto out;
+	}
+
+	if (saddr_low == SBI_SHMEM_DISABLE && saddr_high == SBI_SHMEM_DISABLE) {
+		kvm_pmu_clear_snapshot_area(vcpu);
+		return 0;
+	}
+
+	saddr = saddr_low;
+
+	if (saddr_high != 0) {
+		if (IS_ENABLED(CONFIG_32BIT))
+			saddr |= ((gpa_t)saddr << 32);
+		else
+			sbiret = SBI_ERR_INVALID_ADDRESS;
+		goto out;
+	}
+
+	hva = kvm_vcpu_gfn_to_hva_prot(vcpu, saddr >> PAGE_SHIFT, &writable);
+	if (kvm_is_error_hva(hva) || !writable) {
+		sbiret = SBI_ERR_INVALID_ADDRESS;
+		goto out;
+	}
+
+	kvpmu->sdata = kzalloc(snapshot_area_size, GFP_ATOMIC);
+	if (!kvpmu->sdata)
+		return -ENOMEM;
+
+	if (kvm_vcpu_write_guest(vcpu, saddr, kvpmu->sdata, snapshot_area_size)) {
+		kfree(kvpmu->sdata);
+		sbiret = SBI_ERR_FAILURE;
+		goto out;
+	}
+
+	kvpmu->snapshot_addr = saddr;
+
+out:
+	retdata->err_val = sbiret;
+
+	return 0;
+}
+
 int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu,
 				struct kvm_vcpu_sbi_return *retdata)
 {
@@ -344,20 +419,38 @@  int kvm_riscv_vcpu_pmu_ctr_start(struct kvm_vcpu *vcpu, unsigned long ctr_base,
 	int i, pmc_index, sbiret = 0;
 	struct kvm_pmc *pmc;
 	int fevent_code;
+	bool snap_flag_set = flags & SBI_PMU_START_FLAG_INIT_SNAPSHOT;
 
 	if (kvm_pmu_validate_counter_mask(kvpmu, ctr_base, ctr_mask) < 0) {
 		sbiret = SBI_ERR_INVALID_PARAM;
 		goto out;
 	}
 
+	if (snap_flag_set) {
+		if (kvpmu->snapshot_addr == INVALID_GPA) {
+			sbiret = SBI_ERR_NO_SHMEM;
+			goto out;
+		}
+		if (kvm_vcpu_read_guest(vcpu, kvpmu->snapshot_addr, kvpmu->sdata,
+					sizeof(struct riscv_pmu_snapshot_data))) {
+			pr_warn("Unable to read snapshot shared memory while starting counters\n");
+			sbiret = SBI_ERR_FAILURE;
+			goto out;
+		}
+	}
 	/* Start the counters that have been configured and requested by the guest */
 	for_each_set_bit(i, &ctr_mask, RISCV_MAX_COUNTERS) {
 		pmc_index = i + ctr_base;
 		if (!test_bit(pmc_index, kvpmu->pmc_in_use))
 			continue;
 		pmc = &kvpmu->pmc[pmc_index];
-		if (flags & SBI_PMU_START_FLAG_SET_INIT_VALUE)
+		if (flags & SBI_PMU_START_FLAG_SET_INIT_VALUE) {
 			pmc->counter_val = ival;
+		} else if (snap_flag_set) {
+			/* The counter index in the snapshot are relative to the counter base */
+			pmc->counter_val = kvpmu->sdata->ctr_values[i];
+		}
+
 		if (pmc->cinfo.type == SBI_PMU_CTR_TYPE_FW) {
 			fevent_code = get_event_code(pmc->event_idx);
 			if (fevent_code >= SBI_PMU_FW_MAX) {
@@ -398,14 +491,22 @@  int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
 {
 	struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
 	int i, pmc_index, sbiret = 0;
+	u64 enabled, running;
 	struct kvm_pmc *pmc;
 	int fevent_code;
+	bool snap_flag_set = flags & SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT;
+	bool shmem_needs_update = false;
 
 	if (kvm_pmu_validate_counter_mask(kvpmu, ctr_base, ctr_mask) < 0) {
 		sbiret = SBI_ERR_INVALID_PARAM;
 		goto out;
 	}
 
+	if (snap_flag_set && kvpmu->snapshot_addr == INVALID_GPA) {
+		sbiret = SBI_ERR_NO_SHMEM;
+		goto out;
+	}
+
 	/* Stop the counters that have been configured and requested by the guest */
 	for_each_set_bit(i, &ctr_mask, RISCV_MAX_COUNTERS) {
 		pmc_index = i + ctr_base;
@@ -438,12 +539,28 @@  int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
 		} else {
 			sbiret = SBI_ERR_INVALID_PARAM;
 		}
+
+		if (snap_flag_set && !sbiret) {
+			if (pmc->cinfo.type == SBI_PMU_CTR_TYPE_FW)
+				pmc->counter_val = kvpmu->fw_event[fevent_code].value;
+			else if (pmc->perf_event)
+				pmc->counter_val += perf_event_read_value(pmc->perf_event,
+									  &enabled, &running);
+			/* TODO: Add counter overflow support when sscofpmf support is added */
+			kvpmu->sdata->ctr_values[i] = pmc->counter_val;
+			shmem_needs_update = true;
+		}
+
 		if (flags & SBI_PMU_STOP_FLAG_RESET) {
 			pmc->event_idx = SBI_PMU_EVENT_IDX_INVALID;
 			clear_bit(pmc_index, kvpmu->pmc_in_use);
 		}
 	}
 
+	if (shmem_needs_update)
+		kvm_vcpu_write_guest(vcpu, kvpmu->snapshot_addr, kvpmu->sdata,
+					     sizeof(struct riscv_pmu_snapshot_data));
+
 out:
 	retdata->err_val = sbiret;
 
@@ -566,6 +683,7 @@  void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
 	kvpmu->num_hw_ctrs = num_hw_ctrs + 1;
 	kvpmu->num_fw_ctrs = SBI_PMU_FW_MAX;
 	memset(&kvpmu->fw_event, 0, SBI_PMU_FW_MAX * sizeof(struct kvm_fw_event));
+	kvpmu->snapshot_addr = INVALID_GPA;
 
 	if (kvpmu->num_hw_ctrs > RISCV_KVM_MAX_HW_CTRS) {
 		pr_warn_once("Limiting the hardware counters to 32 as specified by the ISA");
@@ -625,6 +743,7 @@  void kvm_riscv_vcpu_pmu_deinit(struct kvm_vcpu *vcpu)
 	}
 	bitmap_zero(kvpmu->pmc_in_use, RISCV_MAX_COUNTERS);
 	memset(&kvpmu->fw_event, 0, SBI_PMU_FW_MAX * sizeof(struct kvm_fw_event));
+	kvm_pmu_clear_snapshot_area(vcpu);
 }
 
 void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu)
diff --git a/arch/riscv/kvm/vcpu_sbi_pmu.c b/arch/riscv/kvm/vcpu_sbi_pmu.c
index e1633606c98b..d3e7625fb2d2 100644
--- a/arch/riscv/kvm/vcpu_sbi_pmu.c
+++ b/arch/riscv/kvm/vcpu_sbi_pmu.c
@@ -64,6 +64,9 @@  static int kvm_sbi_ext_pmu_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	case SBI_EXT_PMU_COUNTER_FW_READ:
 		ret = kvm_riscv_vcpu_pmu_ctr_read(vcpu, cp->a0, retdata);
 		break;
+	case SBI_EXT_PMU_SNAPSHOT_SET_SHMEM:
+		ret = kvm_riscv_vcpu_pmu_snapshot_set_shmem(vcpu, cp->a0, cp->a1, cp->a2, retdata);
+		break;
 	default:
 		retdata->err_val = SBI_ERR_NOT_SUPPORTED;
 	}

[v5,12/22] RISC-V: KVM: Implement SBI PMU Snapshot feature

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