[PATCH v2 00/15] riscv: add SBI FWFT misaligned exception delegation support

[PATCH v2 00/15] riscv: add SBI FWFT misaligned exception delegation support

[Clément Léger]

The SBI Firmware Feature extension allows the S-mode to request some
specific features (either hardware or software) to be enabled. This
series uses this extension to request misaligned access exception
delegation to S-mode in order to let the kernel handle it. It also adds
support for the KVM FWFT SBI extension based on the misaligned access
handling infrastructure.

FWFT SBI extension is part of the SBI V3.0 specifications [1]. It can be
tested using the qemu provided at [2] which contains the series from
[3]. kvm-unit-tests [4] can be used inside kvm to tests the correct
delegation of misaligned exceptions. Upstream OpenSBI can be used.

The tests can be run using the included kselftest:

$ qemu-system-riscv64 \
	-cpu rv64,trap-misaligned-access=true,v=true \
	-M virt \
	-m 1024M \
	-bios fw_dynamic.bin \
	-kernel Image
 ...

 # ./misaligned
 TAP version 13
 1..23
 # Starting 23 tests from 1 test cases.
 #  RUN           global.gp_load_lh ...
 #            OK  global.gp_load_lh
 ok 1 global.gp_load_lh
 #  RUN           global.gp_load_lhu ...
 #            OK  global.gp_load_lhu
 ok 2 global.gp_load_lhu
 #  RUN           global.gp_load_lw ...
 #            OK  global.gp_load_lw
 ok 3 global.gp_load_lw
 #  RUN           global.gp_load_lwu ...
 #            OK  global.gp_load_lwu
 ok 4 global.gp_load_lwu
 #  RUN           global.gp_load_ld ...
 #            OK  global.gp_load_ld
 ok 5 global.gp_load_ld
 #  RUN           global.gp_load_c_lw ...
 #            OK  global.gp_load_c_lw
 ok 6 global.gp_load_c_lw
 #  RUN           global.gp_load_c_ld ...
 #            OK  global.gp_load_c_ld
 ok 7 global.gp_load_c_ld
 #  RUN           global.gp_load_c_ldsp ...
 #            OK  global.gp_load_c_ldsp
 ok 8 global.gp_load_c_ldsp
 #  RUN           global.gp_load_sh ...
 #            OK  global.gp_load_sh
 ok 9 global.gp_load_sh
 #  RUN           global.gp_load_sw ...
 #            OK  global.gp_load_sw
 ok 10 global.gp_load_sw
 #  RUN           global.gp_load_sd ...
 #            OK  global.gp_load_sd
 ok 11 global.gp_load_sd
 #  RUN           global.gp_load_c_sw ...
 #            OK  global.gp_load_c_sw
 ok 12 global.gp_load_c_sw
 #  RUN           global.gp_load_c_sd ...
 #            OK  global.gp_load_c_sd
 ok 13 global.gp_load_c_sd
 #  RUN           global.gp_load_c_sdsp ...
 #            OK  global.gp_load_c_sdsp
 ok 14 global.gp_load_c_sdsp
 #  RUN           global.fpu_load_flw ...
 #            OK  global.fpu_load_flw
 ok 15 global.fpu_load_flw
 #  RUN           global.fpu_load_fld ...
 #            OK  global.fpu_load_fld
 ok 16 global.fpu_load_fld
 #  RUN           global.fpu_load_c_fld ...
 #            OK  global.fpu_load_c_fld
 ok 17 global.fpu_load_c_fld
 #  RUN           global.fpu_load_c_fldsp ...
 #            OK  global.fpu_load_c_fldsp
 ok 18 global.fpu_load_c_fldsp
 #  RUN           global.fpu_store_fsw ...
 #            OK  global.fpu_store_fsw
 ok 19 global.fpu_store_fsw
 #  RUN           global.fpu_store_fsd ...
 #            OK  global.fpu_store_fsd
 ok 20 global.fpu_store_fsd
 #  RUN           global.fpu_store_c_fsd ...
 #            OK  global.fpu_store_c_fsd
 ok 21 global.fpu_store_c_fsd
 #  RUN           global.fpu_store_c_fsdsp ...
 #            OK  global.fpu_store_c_fsdsp
 ok 22 global.fpu_store_c_fsdsp
 #  RUN           global.gen_sigbus ...
 [12797.988647] misaligned[618]: unhandled signal 7 code 0x1 at 0x0000000000014dc0 in misaligned[4dc0,10000+76000]
 [12797.988990] CPU: 0 UID: 0 PID: 618 Comm: misaligned Not tainted 6.13.0-rc6-00008-g4ec4468967c9-dirty #51
 [12797.989169] Hardware name: riscv-virtio,qemu (DT)
 [12797.989264] epc : 0000000000014dc0 ra : 0000000000014d00 sp : 00007fffe165d100
 [12797.989407]  gp : 000000000008f6e8 tp : 0000000000095760 t0 : 0000000000000008
 [12797.989544]  t1 : 00000000000965d8 t2 : 000000000008e830 s0 : 00007fffe165d160
 [12797.989692]  s1 : 000000000000001a a0 : 0000000000000000 a1 : 0000000000000002
 [12797.989831]  a2 : 0000000000000000 a3 : 0000000000000000 a4 : ffffffffdeadbeef
 [12797.989964]  a5 : 000000000008ef61 a6 : 626769735f6e0000 a7 : fffffffffffff000
 [12797.990094]  s2 : 0000000000000001 s3 : 00007fffe165d838 s4 : 00007fffe165d848
 [12797.990238]  s5 : 000000000000001a s6 : 0000000000010442 s7 : 0000000000010200
 [12797.990391]  s8 : 000000000000003a s9 : 0000000000094508 s10: 0000000000000000
 [12797.990526]  s11: 0000555567460668 t3 : 00007fffe165d070 t4 : 00000000000965d0
 [12797.990656]  t5 : fefefefefefefeff t6 : 0000000000000073
 [12797.990756] status: 0000000200004020 badaddr: 000000000008ef61 cause: 0000000000000006
 [12797.990911] Code: 8793 8791 3423 fcf4 3783 fc84 c737 dead 0713 eef7 (c398) 0001
 #            OK  global.gen_sigbus
 ok 23 global.gen_sigbus
 # PASSED: 23 / 23 tests passed.
 # Totals: pass:23 fail:0 xfail:0 xpass:0 skip:0 error:0

With kvm-tools:

 # lkvm run -k sbi.flat -m 128
  Info: # lkvm run -k sbi.flat -m 128 -c 1 --name guest-97
  Info: Removed ghost socket file "/root/.lkvm//guest-97.sock".

 ##########################################################################
 #    kvm-unit-tests
 ##########################################################################

 ... [test messages elided]
 PASS: sbi: fwft: FWFT extension probing no error
 PASS: sbi: fwft: get/set reserved feature 0x6 error == SBI_ERR_DENIED
 PASS: sbi: fwft: get/set reserved feature 0x3fffffff error == SBI_ERR_DENIED
 PASS: sbi: fwft: get/set reserved feature 0x80000000 error == SBI_ERR_DENIED
 PASS: sbi: fwft: get/set reserved feature 0xbfffffff error == SBI_ERR_DENIED
 PASS: sbi: fwft: misaligned_deleg: Get misaligned deleg feature no error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature invalid value error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature invalid value error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value no error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value 0
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value no error
 PASS: sbi: fwft: misaligned_deleg: Set misaligned deleg feature value 1
 PASS: sbi: fwft: misaligned_deleg: Verify misaligned load exception trap in supervisor
 SUMMARY: 50 tests, 2 unexpected failures, 12 skipped

This series is available at [6].

Link: https://github.com/riscv-non-isa/riscv-sbi-doc/releases/download/vv3.0-rc2/riscv-sbi.pdf [1]
Link: https://github.com/rivosinc/qemu/tree/dev/cleger/misaligned [2]
Link: https://lore.kernel.org/all/20241211211933.198792-3-fkonrad@amd.com/T/ [3]
Link: https://github.com/clementleger/kvm-unit-tests/tree/dev/cleger/fwft_v1 [4]
Link: https://github.com/clementleger/unaligned_test [5]
Link: https://github.com/rivosinc/linux/tree/dev/cleger/fwft_v1 [6]
---

V2:
 - Added Kselftest for misaligned testing
 - Added get_user() usage instead of __get_user()
 - Reenable interrupt when possible in misaligned access handling
 - Document that riscv supports unaligned-traps
 - Fix KVM extension state when an init function is present
 - Rework SBI misaligned accesses trap delegation code
 - Added support for CPU hotplugging
 - Added KVM SBI reset callback
 - Added reset for KVM SBI FWFT lock
 - Return SBI_ERR_DENIED_LOCKED when LOCK flag is set

Clément Léger (15):
  riscv: add Firmware Feature (FWFT) SBI extensions definitions
  riscv: misaligned: request misaligned exception from SBI
  riscv: misaligned: use on_each_cpu() for scalar misaligned access
    probing
  riscv: misaligned: use correct CONFIG_ ifdef for
    misaligned_access_speed
  riscv: misaligned: move emulated access uniformity check in a function
  riscv: misaligned: add a function to check misalign trap delegability
  riscv: misaligned: factorize trap handling
  riscv: misaligned: enable IRQs while handling misaligned accesses
  riscv: misaligned: use get_user() instead of __get_user()
  Documentation/sysctl: add riscv to unaligned-trap supported archs
  selftests: riscv: add misaligned access testing
  RISC-V: KVM: add SBI extension init()/deinit() functions
  RISC-V: KVM: add SBI extension reset callback
  RISC-V: KVM: add support for FWFT SBI extension
  RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

 Documentation/admin-guide/sysctl/kernel.rst   |   4 +-
 arch/riscv/include/asm/cpufeature.h           |   8 +-
 arch/riscv/include/asm/kvm_host.h             |   5 +-
 arch/riscv/include/asm/kvm_vcpu_sbi.h         |  12 +
 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h    |  37 +++
 arch/riscv/include/asm/sbi.h                  |  33 +++
 arch/riscv/include/uapi/asm/kvm.h             |   1 +
 arch/riscv/kernel/traps.c                     |  57 ++--
 arch/riscv/kernel/traps_misaligned.c          | 138 +++++++++-
 arch/riscv/kernel/unaligned_access_speed.c    |  11 +-
 arch/riscv/kvm/Makefile                       |   1 +
 arch/riscv/kvm/vcpu.c                         |   7 +-
 arch/riscv/kvm/vcpu_sbi.c                     |  58 ++++
 arch/riscv/kvm/vcpu_sbi_fwft.c                | 226 ++++++++++++++++
 arch/riscv/kvm/vcpu_sbi_sta.c                 |   3 +-
 .../selftests/riscv/misaligned/.gitignore     |   1 +
 .../selftests/riscv/misaligned/Makefile       |  12 +
 .../selftests/riscv/misaligned/common.S       |  33 +++
 .../testing/selftests/riscv/misaligned/fpu.S  | 180 +++++++++++++
 tools/testing/selftests/riscv/misaligned/gp.S | 103 +++++++
 .../selftests/riscv/misaligned/misaligned.c   | 254 ++++++++++++++++++
 21 files changed, 1137 insertions(+), 47 deletions(-)
 create mode 100644 arch/riscv/include/asm/kvm_vcpu_sbi_fwft.h
 create mode 100644 arch/riscv/kvm/vcpu_sbi_fwft.c
 create mode 100644 tools/testing/selftests/riscv/misaligned/.gitignore
 create mode 100644 tools/testing/selftests/riscv/misaligned/Makefile
 create mode 100644 tools/testing/selftests/riscv/misaligned/common.S
 create mode 100644 tools/testing/selftests/riscv/misaligned/fpu.S
 create mode 100644 tools/testing/selftests/riscv/misaligned/gp.S
 create mode 100644 tools/testing/selftests/riscv/misaligned/misaligned.c

-- 
2.47.2

[PATCH v2 01/15] riscv: add Firmware Feature (FWFT) SBI extensions definitions

[Clément Léger]

The Firmware Features extension (FWFT) was added as part of the SBI 3.0
specification. Add SBI definitions to use this extension.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Tested-by: Samuel Holland <samuel.holland@sifive.com>
---
 arch/riscv/include/asm/sbi.h | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 3d250824178b..d373b5c08039 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -35,6 +35,7 @@ enum sbi_ext_id {
 	SBI_EXT_DBCN = 0x4442434E,
 	SBI_EXT_STA = 0x535441,
 	SBI_EXT_NACL = 0x4E41434C,
+	SBI_EXT_FWFT = 0x46574654,
 
 	/* Experimentals extensions must lie within this range */
 	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
@@ -402,6 +403,33 @@ enum sbi_ext_nacl_feature {
 #define SBI_NACL_SHMEM_SRET_X(__i)		((__riscv_xlen / 8) * (__i))
 #define SBI_NACL_SHMEM_SRET_X_LAST		31
 
+/* SBI function IDs for FW feature extension */
+#define SBI_EXT_FWFT_SET		0x0
+#define SBI_EXT_FWFT_GET		0x1
+
+enum sbi_fwft_feature_t {
+	SBI_FWFT_MISALIGNED_EXC_DELEG		= 0x0,
+	SBI_FWFT_LANDING_PAD			= 0x1,
+	SBI_FWFT_SHADOW_STACK			= 0x2,
+	SBI_FWFT_DOUBLE_TRAP			= 0x3,
+	SBI_FWFT_PTE_AD_HW_UPDATING		= 0x4,
+	SBI_FWFT_POINTER_MASKING_PMLEN		= 0x5,
+	SBI_FWFT_LOCAL_RESERVED_START		= 0x6,
+	SBI_FWFT_LOCAL_RESERVED_END		= 0x3fffffff,
+	SBI_FWFT_LOCAL_PLATFORM_START		= 0x40000000,
+	SBI_FWFT_LOCAL_PLATFORM_END		= 0x7fffffff,
+
+	SBI_FWFT_GLOBAL_RESERVED_START		= 0x80000000,
+	SBI_FWFT_GLOBAL_RESERVED_END		= 0xbfffffff,
+	SBI_FWFT_GLOBAL_PLATFORM_START		= 0xc0000000,
+	SBI_FWFT_GLOBAL_PLATFORM_END		= 0xffffffff,
+};
+
+#define SBI_FWFT_PLATFORM_FEATURE_BIT		(1 << 30)
+#define SBI_FWFT_GLOBAL_FEATURE_BIT		(1 << 31)
+
+#define SBI_FWFT_SET_FLAG_LOCK			(1 << 0)
+
 /* SBI spec version fields */
 #define SBI_SPEC_VERSION_DEFAULT	0x1
 #define SBI_SPEC_VERSION_MAJOR_SHIFT	24
@@ -419,6 +447,11 @@ enum sbi_ext_nacl_feature {
 #define SBI_ERR_ALREADY_STARTED -7
 #define SBI_ERR_ALREADY_STOPPED -8
 #define SBI_ERR_NO_SHMEM	-9
+#define SBI_ERR_INVALID_STATE	-10
+#define SBI_ERR_BAD_RANGE	-11
+#define SBI_ERR_TIMEOUT		-12
+#define SBI_ERR_IO		-13
+#define SBI_ERR_DENIED_LOCKED	-14
 
 extern unsigned long sbi_spec_version;
 struct sbiret {
-- 
2.47.2

[PATCH v2 02/15] riscv: misaligned: request misaligned exception from SBI

[Clément Léger]

Now that the kernel can handle misaligned accesses in S-mode, request
misaligned access exception delegation from SBI. This uses the FWFT SBI
extension defined in SBI version 3.0.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/include/asm/cpufeature.h        |  3 +-
 arch/riscv/kernel/traps_misaligned.c       | 96 +++++++++++++++++++++-
 arch/riscv/kernel/unaligned_access_speed.c | 11 ++-
 3 files changed, 105 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 569140d6e639..ad7d26788e6a 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -64,8 +64,9 @@ void __init riscv_user_isa_enable(void);
 	_RISCV_ISA_EXT_DATA(_name, _id, _sub_exts, ARRAY_SIZE(_sub_exts), _validate)
 
 bool check_unaligned_access_emulated_all_cpus(void);
+void unaligned_access_init(void);
+int cpu_online_unaligned_access_init(unsigned int cpu);
 #if defined(CONFIG_RISCV_SCALAR_MISALIGNED)
-void check_unaligned_access_emulated(struct work_struct *work __always_unused);
 void unaligned_emulation_finish(void);
 bool unaligned_ctl_available(void);
 DECLARE_PER_CPU(long, misaligned_access_speed);
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 7cc108aed74e..66eef398bad4 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -16,6 +16,7 @@
 #include <asm/entry-common.h>
 #include <asm/hwprobe.h>
 #include <asm/cpufeature.h>
+#include <asm/sbi.h>
 #include <asm/vector.h>
 
 #define INSN_MATCH_LB			0x3
@@ -635,7 +636,7 @@ bool check_vector_unaligned_access_emulated_all_cpus(void)
 
 static bool unaligned_ctl __read_mostly;
 
-void check_unaligned_access_emulated(struct work_struct *work __always_unused)
+static void check_unaligned_access_emulated(struct work_struct *work __always_unused)
 {
 	int cpu = smp_processor_id();
 	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
@@ -646,6 +647,13 @@ void check_unaligned_access_emulated(struct work_struct *work __always_unused)
 	__asm__ __volatile__ (
 		"       "REG_L" %[tmp], 1(%[ptr])\n"
 		: [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
+}
+
+static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
+{
+	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
+
+	check_unaligned_access_emulated(NULL);
 
 	/*
 	 * If unaligned_ctl is already set, this means that we detected that all
@@ -654,9 +662,10 @@ void check_unaligned_access_emulated(struct work_struct *work __always_unused)
 	 */
 	if (unlikely(unaligned_ctl && (*mas_ptr != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED))) {
 		pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
-		while (true)
-			cpu_relax();
+		return -EINVAL;
 	}
+
+	return 0;
 }
 
 bool check_unaligned_access_emulated_all_cpus(void)
@@ -688,4 +697,85 @@ bool check_unaligned_access_emulated_all_cpus(void)
 {
 	return false;
 }
+static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
+{
+	return 0;
+}
 #endif
+
+#ifdef CONFIG_RISCV_SBI
+
+struct misaligned_deleg_req {
+	atomic_t error;
+};
+
+static int sbi_request_unaligned_delegation(void)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_FWFT, SBI_EXT_FWFT_SET,
+			SBI_FWFT_MISALIGNED_EXC_DELEG, 1, 0, 0, 0, 0);
+
+	return sbi_err_map_linux_errno(ret.error);
+}
+
+static bool misaligned_traps_delegated;
+
+static int cpu_online_sbi_unaligned_setup(unsigned int cpu)
+{
+	if (sbi_request_unaligned_delegation() && misaligned_traps_delegated) {
+		pr_crit("Misaligned trap delegation non homogeneous (expected delegated)");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void
+cpu_unaligned_sbi_request_delegation(void *arg)
+{
+	struct misaligned_deleg_req *req = arg;
+
+	if (sbi_request_unaligned_delegation())
+		atomic_set(&req->error, 1);
+}
+
+static void unaligned_sbi_request_delegation(void)
+{
+	struct misaligned_deleg_req req = {.error = ATOMIC_INIT(0)};
+
+	on_each_cpu(cpu_unaligned_sbi_request_delegation, &req, 1);
+	if (atomic_read(&req.error) == 0) {
+		pr_info("SBI misaligned access exception delegation ok\n");
+		misaligned_traps_delegated = true;
+		/*
+		 * Note that we don't have to take any specific action here, if
+		 * the delegation is successful, then
+		 * check_unaligned_access_emulated() will verify that indeed the
+		 * platform traps on misaligned accesses.
+		 */
+	}
+}
+
+void unaligned_access_init(void)
+{
+	if (sbi_probe_extension(SBI_EXT_FWFT) > 0)
+		unaligned_sbi_request_delegation();
+}
+#else
+void unaligned_access_init(void) {}
+
+static int cpu_online_sbi_unaligned_setup(unsigned int cpu __always_unused)
+{
+	return 0;
+}
+#endif
+
+int cpu_online_unaligned_access_init(unsigned int cpu)
+{
+	int ret = cpu_online_sbi_unaligned_setup(cpu);
+	if (ret)
+		return ret;
+
+	return cpu_online_check_unaligned_access_emulated(cpu);
+}
diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
index 91f189cf1611..2f3aba073297 100644
--- a/arch/riscv/kernel/unaligned_access_speed.c
+++ b/arch/riscv/kernel/unaligned_access_speed.c
@@ -188,13 +188,20 @@ arch_initcall_sync(lock_and_set_unaligned_access_static_branch);
 
 static int riscv_online_cpu(unsigned int cpu)
 {
+	int ret;
 	static struct page *buf;
 
 	/* We are already set since the last check */
 	if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN)
 		goto exit;
 
-	check_unaligned_access_emulated(NULL);
+	ret = cpu_online_unaligned_access_init(cpu);
+	if (ret)
+		return ret;
+
+	if (per_cpu(misaligned_access_speed, cpu) == RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
+		goto exit;
+
 	buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
 	if (!buf) {
 		pr_warn("Allocation failure, not measuring misaligned performance\n");
@@ -403,6 +410,8 @@ static int check_unaligned_access_all_cpus(void)
 {
 	bool all_cpus_emulated, all_cpus_vec_unsupported;
 
+	unaligned_access_init();
+
 	all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
 	all_cpus_vec_unsupported = check_vector_unaligned_access_emulated_all_cpus();
 
-- 
2.47.2

[PATCH v2 03/15] riscv: misaligned: use on_each_cpu() for scalar misaligned access probing

[Clément Léger]

schedule_on_each_cpu() was used without any good reason while documented
as very slow. This call was in the boot path, so better use
on_each_cpu() for scalar misaligned checking. Vector misaligned check
still needs to use schedule_on_each_cpu() since it requires irqs to be
enabled but that's less of a problem since this code is ran in a kthread.
Add a comment to explicit that.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/kernel/traps_misaligned.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 66eef398bad4..eb9157e3af73 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -616,6 +616,11 @@ bool check_vector_unaligned_access_emulated_all_cpus(void)
 		return false;
 	}
 
+	/*
+	 * While being documented as very slow, schedule_on_each_cpu() is used
+	 * since kernel_vector_begin() that is called inside the vector code
+	 * expects irqs to be enabled or it will panic().
+	 */
 	schedule_on_each_cpu(check_vector_unaligned_access_emulated);
 
 	for_each_online_cpu(cpu)
@@ -636,7 +641,7 @@ bool check_vector_unaligned_access_emulated_all_cpus(void)
 
 static bool unaligned_ctl __read_mostly;
 
-static void check_unaligned_access_emulated(struct work_struct *work __always_unused)
+static void check_unaligned_access_emulated(void *arg __always_unused)
 {
 	int cpu = smp_processor_id();
 	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
@@ -677,7 +682,7 @@ bool check_unaligned_access_emulated_all_cpus(void)
 	 * accesses emulated since tasks requesting such control can run on any
 	 * CPU.
 	 */
-	schedule_on_each_cpu(check_unaligned_access_emulated);
+	on_each_cpu(check_unaligned_access_emulated, NULL, 1);
 
 	for_each_online_cpu(cpu)
 		if (per_cpu(misaligned_access_speed, cpu)
-- 
2.47.2

[PATCH v2 04/15] riscv: misaligned: use correct CONFIG_ ifdef for misaligned_access_speed

[Clément Léger]

misaligned_access_speed is defined under CONFIG_RISCV_SCALAR_MISALIGNED
but was used under CONFIG_RISCV_PROBE_UNALIGNED_ACCESS. Fix that by
using the correct config option.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/kernel/traps_misaligned.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index eb9157e3af73..57ded7e74dd8 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -362,7 +362,7 @@ static int handle_scalar_misaligned_load(struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
 
-#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
+#ifdef CONFIG_RISCV_SCALAR_MISALIGNED
 	*this_cpu_ptr(&misaligned_access_speed) = RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED;
 #endif
 
-- 
2.47.2

[PATCH v2 05/15] riscv: misaligned: move emulated access uniformity check in a function

[Clément Léger]

Split the code that check for the uniformity of misaligned accesses
performance on all cpus from check_unaligned_access_emulated_all_cpus()
to its own function which will be used for delegation check. No
functional changes intended.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/kernel/traps_misaligned.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 57ded7e74dd8..7d6185deea33 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -673,10 +673,20 @@ static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
 	return 0;
 }
 
-bool check_unaligned_access_emulated_all_cpus(void)
+static bool all_cpus_unaligned_scalar_access_emulated(void)
 {
 	int cpu;
 
+	for_each_online_cpu(cpu)
+		if (per_cpu(misaligned_access_speed, cpu) !=
+		    RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
+			return false;
+
+	return true;
+}
+
+bool check_unaligned_access_emulated_all_cpus(void)
+{
 	/*
 	 * We can only support PR_UNALIGN controls if all CPUs have misaligned
 	 * accesses emulated since tasks requesting such control can run on any
@@ -684,10 +694,8 @@ bool check_unaligned_access_emulated_all_cpus(void)
 	 */
 	on_each_cpu(check_unaligned_access_emulated, NULL, 1);
 
-	for_each_online_cpu(cpu)
-		if (per_cpu(misaligned_access_speed, cpu)
-		    != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
-			return false;
+	if (!all_cpus_unaligned_scalar_access_emulated())
+		return false;
 
 	unaligned_ctl = true;
 	return true;
-- 
2.47.2

[PATCH v2 06/15] riscv: misaligned: add a function to check misalign trap delegability

[Clément Léger]

Checking for the delegability of the misaligned access trap is needed
for the KVM FWFT extension implementation. Add a function to get the
delegability of the misaligned trap exception.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/include/asm/cpufeature.h  |  5 +++++
 arch/riscv/kernel/traps_misaligned.c | 17 +++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index ad7d26788e6a..8b97cba99fc3 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -69,12 +69,17 @@ int cpu_online_unaligned_access_init(unsigned int cpu);
 #if defined(CONFIG_RISCV_SCALAR_MISALIGNED)
 void unaligned_emulation_finish(void);
 bool unaligned_ctl_available(void);
+bool misaligned_traps_can_delegate(void);
 DECLARE_PER_CPU(long, misaligned_access_speed);
 #else
 static inline bool unaligned_ctl_available(void)
 {
 	return false;
 }
+static inline bool misaligned_traps_can_delegate(void)
+{
+	return false;
+}
 #endif
 
 bool check_vector_unaligned_access_emulated_all_cpus(void);
diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 7d6185deea33..1d523cf96ff0 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -716,6 +716,8 @@ static int cpu_online_check_unaligned_access_emulated(unsigned int cpu)
 }
 #endif
 
+static bool misaligned_traps_delegated;
+
 #ifdef CONFIG_RISCV_SBI
 
 struct misaligned_deleg_req {
@@ -732,8 +734,6 @@ static int sbi_request_unaligned_delegation(void)
 	return sbi_err_map_linux_errno(ret.error);
 }
 
-static bool misaligned_traps_delegated;
-
 static int cpu_online_sbi_unaligned_setup(unsigned int cpu)
 {
 	if (sbi_request_unaligned_delegation() && misaligned_traps_delegated) {
@@ -782,6 +782,7 @@ static int cpu_online_sbi_unaligned_setup(unsigned int cpu __always_unused)
 {
 	return 0;
 }
+
 #endif
 
 int cpu_online_unaligned_access_init(unsigned int cpu)
@@ -792,3 +793,15 @@ int cpu_online_unaligned_access_init(unsigned int cpu)
 
 	return cpu_online_check_unaligned_access_emulated(cpu);
 }
+
+bool misaligned_traps_can_delegate(void)
+{
+	/*
+	 * Either we successfully requested misaligned traps delegation for all
+	 * CPUS or the SBI does not implemented FWFT extension but delegated the
+	 * exception by default.
+	 */
+	return misaligned_traps_delegated ||
+	       all_cpus_unaligned_scalar_access_emulated();
+}
+EXPORT_SYMBOL_GPL(misaligned_traps_can_delegate);
\ No newline at end of file
-- 
2.47.2

[PATCH v2 07/15] riscv: misaligned: factorize trap handling

[Clément Léger]

misaligned accesses traps are not nmi and should be treated as normal
one using irqentry_enter()/exit(). Since both load/store and user/kernel
should use almost the same path and that we are going to add some code
around that, factorize it.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/kernel/traps.c | 49 ++++++++++++++++-----------------------
 1 file changed, 20 insertions(+), 29 deletions(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 8ff8e8b36524..55d9f3450398 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -198,47 +198,38 @@ asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *re
 DO_ERROR_INFO(do_trap_load_fault,
 	SIGSEGV, SEGV_ACCERR, "load access fault");
 
-asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
+enum misaligned_access_type {
+	MISALIGNED_STORE,
+	MISALIGNED_LOAD,
+};
+
+static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type type)
 {
-	if (user_mode(regs)) {
-		irqentry_enter_from_user_mode(regs);
+	irqentry_state_t state = irqentry_enter(regs);
 
+	if (type ==  MISALIGNED_LOAD) {
 		if (handle_misaligned_load(regs))
 			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
-			      "Oops - load address misaligned");
-
-		irqentry_exit_to_user_mode(regs);
+				      "Oops - load address misaligned");
 	} else {
-		irqentry_state_t state = irqentry_nmi_enter(regs);
-
-		if (handle_misaligned_load(regs))
+		if (handle_misaligned_store(regs))
 			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
-			      "Oops - load address misaligned");
-
-		irqentry_nmi_exit(regs, state);
+				      "Oops - store (or AMO) address misaligned");
 	}
+
+	irqentry_exit(regs, state);
 }
 
-asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
+asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
 {
-	if (user_mode(regs)) {
-		irqentry_enter_from_user_mode(regs);
-
-		if (handle_misaligned_store(regs))
-			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
-				"Oops - store (or AMO) address misaligned");
-
-		irqentry_exit_to_user_mode(regs);
-	} else {
-		irqentry_state_t state = irqentry_nmi_enter(regs);
-
-		if (handle_misaligned_store(regs))
-			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
-				"Oops - store (or AMO) address misaligned");
+	do_trap_misaligned(regs, MISALIGNED_LOAD);
+}
 
-		irqentry_nmi_exit(regs, state);
-	}
+asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
+{
+	do_trap_misaligned(regs, MISALIGNED_STORE);
 }
+
 DO_ERROR_INFO(do_trap_store_fault,
 	SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
 DO_ERROR_INFO(do_trap_ecall_s,
-- 
2.47.2

[PATCH v2 08/15] riscv: misaligned: enable IRQs while handling misaligned accesses

[Clément Léger]

We can safely reenable IRQs if they were enabled in the previous
context. This allows to access user memory that could potentially
trigger a page fault.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/kernel/traps.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 55d9f3450398..3eecc2addc41 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -206,6 +206,11 @@ enum misaligned_access_type {
 static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type type)
 {
 	irqentry_state_t state = irqentry_enter(regs);
+	bool enable_irqs = !regs_irqs_disabled(regs);
+
+	/* Enable interrupts if they were enabled in the interrupted context. */
+	if (enable_irqs)
+		local_irq_enable();
 
 	if (type ==  MISALIGNED_LOAD) {
 		if (handle_misaligned_load(regs))
@@ -217,6 +222,9 @@ static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type
 				      "Oops - store (or AMO) address misaligned");
 	}
 
+	if (enable_irqs)
+		local_irq_disable();
+
 	irqentry_exit(regs, state);
 }
 
-- 
2.47.2

[PATCH v2 09/15] riscv: misaligned: use get_user() instead of __get_user()

[Clément Léger]

Now that we can safely handle user memory accesses while in the
misaligned access handlers, use get_user() instead of __get_user() to
have user memory access checks.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/kernel/traps_misaligned.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 1d523cf96ff0..e6685db58bd1 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -269,7 +269,7 @@ static unsigned long get_f32_rs(unsigned long insn, u8 fp_reg_offset,
 	int __ret;					\
 							\
 	if (user_mode(regs)) {				\
-		__ret = __get_user(insn, (type __user *) insn_addr); \
+		__ret = get_user(insn, (type __user *) insn_addr); \
 	} else {					\
 		insn = *(type *)insn_addr;		\
 		__ret = 0;				\
-- 
2.47.2

[PATCH v2 10/15] Documentation/sysctl: add riscv to unaligned-trap supported archs

[Clément Léger]

riscv supports the "unaligned-trap" sysctl variable, add it to the list
of supported architectures.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 Documentation/admin-guide/sysctl/kernel.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index a43b78b4b646..ce3f0dd3666e 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1584,8 +1584,8 @@ unaligned-trap
 
 On architectures where unaligned accesses cause traps, and where this
 feature is supported (``CONFIG_SYSCTL_ARCH_UNALIGN_ALLOW``; currently,
-``arc``, ``parisc`` and ``loongarch``), controls whether unaligned traps
-are caught and emulated (instead of failing).
+``arc``, ``parisc``, ``loongarch`` and ``riscv``), controls whether unaligned
+traps are caught and emulated (instead of failing).
 
 = ========================================================
 0 Do not emulate unaligned accesses.
-- 
2.47.2

[PATCH v2 11/15] selftests: riscv: add misaligned access testing

[Clément Léger]

Now that the kernel can emulate misaligned access and control its
behavior, add a selftest for that. This selftest tests all the currently
emulated instruction (except for the RV32 compressed ones which are left
as a future exercise for a RV32 user). For the FPU instructions, all the
FPU registers are tested.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 .../selftests/riscv/misaligned/.gitignore     |   1 +
 .../selftests/riscv/misaligned/Makefile       |  12 +
 .../selftests/riscv/misaligned/common.S       |  33 +++
 .../testing/selftests/riscv/misaligned/fpu.S  | 180 +++++++++++++
 tools/testing/selftests/riscv/misaligned/gp.S | 103 +++++++
 .../selftests/riscv/misaligned/misaligned.c   | 254 ++++++++++++++++++
 6 files changed, 583 insertions(+)
 create mode 100644 tools/testing/selftests/riscv/misaligned/.gitignore
 create mode 100644 tools/testing/selftests/riscv/misaligned/Makefile
 create mode 100644 tools/testing/selftests/riscv/misaligned/common.S
 create mode 100644 tools/testing/selftests/riscv/misaligned/fpu.S
 create mode 100644 tools/testing/selftests/riscv/misaligned/gp.S
 create mode 100644 tools/testing/selftests/riscv/misaligned/misaligned.c

diff --git a/tools/testing/selftests/riscv/misaligned/.gitignore b/tools/testing/selftests/riscv/misaligned/.gitignore
new file mode 100644
index 000000000000..5eff15a1f981
--- /dev/null
+++ b/tools/testing/selftests/riscv/misaligned/.gitignore
@@ -0,0 +1 @@
+misaligned
diff --git a/tools/testing/selftests/riscv/misaligned/Makefile b/tools/testing/selftests/riscv/misaligned/Makefile
new file mode 100644
index 000000000000..1aa40110c50d
--- /dev/null
+++ b/tools/testing/selftests/riscv/misaligned/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 ARM Limited
+# Originally tools/testing/arm64/abi/Makefile
+
+CFLAGS += -I$(top_srcdir)/tools/include
+
+TEST_GEN_PROGS := misaligned
+
+include ../../lib.mk
+
+$(OUTPUT)/misaligned: misaligned.c fpu.S gp.S
+	$(CC) -g3 -static -o$@ -march=rv64imafdc $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/misaligned/common.S b/tools/testing/selftests/riscv/misaligned/common.S
new file mode 100644
index 000000000000..8fa00035bd5d
--- /dev/null
+++ b/tools/testing/selftests/riscv/misaligned/common.S
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ *     Clément Léger <cleger@rivosinc.com>
+ */
+
+.macro lb_sb temp, offset, src, dst
+	lb \temp, \offset(\src)
+	sb \temp, \offset(\dst)
+.endm
+
+.macro copy_long_to temp, src, dst
+	lb_sb \temp, 0, \src, \dst,
+	lb_sb \temp, 1, \src, \dst,
+	lb_sb \temp, 2, \src, \dst,
+	lb_sb \temp, 3, \src, \dst,
+	lb_sb \temp, 4, \src, \dst,
+	lb_sb \temp, 5, \src, \dst,
+	lb_sb \temp, 6, \src, \dst,
+	lb_sb \temp, 7, \src, \dst,
+.endm
+
+.macro sp_stack_prologue offset
+	addi sp, sp, -8
+	sub sp, sp, \offset
+.endm
+
+.macro sp_stack_epilogue offset
+	add sp, sp, \offset
+	addi sp, sp, 8
+.endm
diff --git a/tools/testing/selftests/riscv/misaligned/fpu.S b/tools/testing/selftests/riscv/misaligned/fpu.S
new file mode 100644
index 000000000000..d008bff58310
--- /dev/null
+++ b/tools/testing/selftests/riscv/misaligned/fpu.S
@@ -0,0 +1,180 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ *     Clément Léger <cleger@rivosinc.com>
+ */
+
+#include "common.S"
+
+#define CASE_ALIGN		4
+
+.macro fpu_load_inst fpreg, inst, precision, load_reg
+.align CASE_ALIGN
+	\inst \fpreg, 0(\load_reg)
+	fmv.\precision fa0, \fpreg
+	j 2f
+.endm
+
+#define flw(__fpreg) fpu_load_inst __fpreg, flw, s, s1
+#define fld(__fpreg) fpu_load_inst __fpreg, fld, d, s1
+#define c_flw(__fpreg) fpu_load_inst __fpreg, c.flw, s, s1
+#define c_fld(__fpreg) fpu_load_inst __fpreg, c.fld, d, s1
+#define c_fldsp(__fpreg) fpu_load_inst __fpreg, c.fldsp, d, sp
+
+.macro fpu_store_inst fpreg, inst, precision, store_reg
+.align CASE_ALIGN
+	fmv.\precision \fpreg, fa0
+	\inst \fpreg, 0(\store_reg)
+	j 2f
+.endm
+
+#define fsw(__fpreg) fpu_store_inst __fpreg, fsw, s, s1
+#define fsd(__fpreg) fpu_store_inst __fpreg, fsd, d, s1
+#define c_fsw(__fpreg) fpu_store_inst __fpreg, c.fsw, s, s1
+#define c_fsd(__fpreg) fpu_store_inst __fpreg, c.fsd, d, s1
+#define c_fsdsp(__fpreg) fpu_store_inst __fpreg, c.fsdsp, d, sp
+
+.macro fp_test_prologue
+	move s1, a1
+	/*
+	 * Compute jump offset to store the correct FP register since we don't
+	 * have indirect FP register access (or at least we don't use this
+	 * extension so that works on all archs)
+	 */
+	sll t0, a0, CASE_ALIGN
+	la t2, 1f
+	add t0, t0, t2
+	jr t0
+.align	CASE_ALIGN
+1:
+.endm
+
+.macro fp_test_prologue_compressed
+	/* FP registers for compressed instructions starts from 8 to 16 */
+	addi a0, a0, -8
+	fp_test_prologue
+.endm
+
+#define fp_test_body_compressed(__inst_func) \
+	__inst_func(f8); \
+	__inst_func(f9); \
+	__inst_func(f10); \
+	__inst_func(f11); \
+	__inst_func(f12); \
+	__inst_func(f13); \
+	__inst_func(f14); \
+	__inst_func(f15); \
+2:
+
+#define fp_test_body(__inst_func) \
+	__inst_func(f0); \
+	__inst_func(f1); \
+	__inst_func(f2); \
+	__inst_func(f3); \
+	__inst_func(f4); \
+	__inst_func(f5); \
+	__inst_func(f6); \
+	__inst_func(f7); \
+	__inst_func(f8); \
+	__inst_func(f9); \
+	__inst_func(f10); \
+	__inst_func(f11); \
+	__inst_func(f12); \
+	__inst_func(f13); \
+	__inst_func(f14); \
+	__inst_func(f15); \
+	__inst_func(f16); \
+	__inst_func(f17); \
+	__inst_func(f18); \
+	__inst_func(f19); \
+	__inst_func(f20); \
+	__inst_func(f21); \
+	__inst_func(f22); \
+	__inst_func(f23); \
+	__inst_func(f24); \
+	__inst_func(f25); \
+	__inst_func(f26); \
+	__inst_func(f27); \
+	__inst_func(f28); \
+	__inst_func(f29); \
+	__inst_func(f30); \
+	__inst_func(f31); \
+2:
+.text
+
+#define __gen_test_inst(__inst, __suffix) \
+.global test_ ## __inst; \
+test_ ## __inst:; \
+	fp_test_prologue ## __suffix; \
+	fp_test_body ## __suffix(__inst); \
+	ret
+
+#define gen_test_inst_compressed(__inst) \
+	.option arch,+c; \
+	__gen_test_inst(c_ ## __inst, _compressed)
+
+#define gen_test_inst(__inst) \
+	.balign 16; \
+	.option push; \
+	.option arch,-c; \
+	__gen_test_inst(__inst, ); \
+	.option pop
+
+.macro fp_test_prologue_load_compressed_sp
+	copy_long_to t0, a1, sp
+.endm
+
+.macro fp_test_epilogue_load_compressed_sp
+.endm
+
+.macro fp_test_prologue_store_compressed_sp
+.endm
+
+.macro fp_test_epilogue_store_compressed_sp
+	copy_long_to t0, sp, a1
+.endm
+
+#define gen_inst_compressed_sp(__inst, __type) \
+	.global test_c_ ## __inst ## sp; \
+	test_c_ ## __inst ## sp:; \
+		sp_stack_prologue a2; \
+		fp_test_prologue_## __type ## _compressed_sp; \
+		fp_test_prologue_compressed; \
+		fp_test_body_compressed(c_ ## __inst ## sp); \
+		fp_test_epilogue_## __type ## _compressed_sp; \
+		sp_stack_epilogue a2; \
+		ret
+
+#define gen_test_load_compressed_sp(__inst) gen_inst_compressed_sp(__inst, load)
+#define gen_test_store_compressed_sp(__inst) gen_inst_compressed_sp(__inst, store)
+
+/*
+ * float_fsw_reg - Set a FP register from a register containing the value
+ * a0 = FP register index to be set
+ * a1 = addr where to store register value
+ * a2 = address offset
+ * a3 = value to be store
+ */
+gen_test_inst(fsw)
+
+/*
+ * float_flw_reg - Get a FP register value and return it
+ * a0 = FP register index to be retrieved
+ * a1 = addr to load register from
+ * a2 = address offset
+ */
+gen_test_inst(flw)
+
+gen_test_inst(fsd)
+#ifdef __riscv_compressed
+gen_test_inst_compressed(fsd)
+gen_test_store_compressed_sp(fsd)
+#endif
+
+gen_test_inst(fld)
+#ifdef __riscv_compressed
+gen_test_inst_compressed(fld)
+gen_test_load_compressed_sp(fld)
+#endif
diff --git a/tools/testing/selftests/riscv/misaligned/gp.S b/tools/testing/selftests/riscv/misaligned/gp.S
new file mode 100644
index 000000000000..f53f4c6d81dd
--- /dev/null
+++ b/tools/testing/selftests/riscv/misaligned/gp.S
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ *     Clément Léger <cleger@rivosinc.com>
+ */
+
+#include "common.S"
+
+.text
+
+.macro __gen_test_inst inst, src_reg
+	\inst a2, 0(\src_reg)
+	move a0, a2
+.endm
+
+.macro gen_func_header func_name, rvc
+	.option arch,\rvc
+	.global test_\func_name
+	test_\func_name:
+.endm
+
+.macro gen_test_inst inst
+	.option push
+	gen_func_header \inst, -c
+	__gen_test_inst \inst, a0
+	.option pop
+	ret
+.endm
+
+.macro __gen_test_inst_c name, src_reg
+	.option push
+	gen_func_header c_\name, +c
+	 __gen_test_inst c.\name, \src_reg
+	.option pop
+	ret
+.endm
+
+.macro gen_test_inst_c name
+ 	__gen_test_inst_c \name, a0
+.endm
+
+
+.macro gen_test_inst_load_c_sp name
+	.option push
+	gen_func_header c_\name\()sp, +c
+	sp_stack_prologue a1
+	copy_long_to t0, a0, sp
+	c.ldsp a0, 0(sp)
+	sp_stack_epilogue a1
+	.option pop
+	ret
+.endm
+
+.macro lb_sp_sb_a0 reg, offset
+	lb_sb \reg, \offset, sp, a0
+.endm
+
+.macro gen_test_inst_store_c_sp inst_name
+	.option push
+	gen_func_header c_\inst_name\()sp, +c
+	/* Misalign stack pointer */
+	sp_stack_prologue a1
+	/* Misalign access */
+	c.sdsp a2, 0(sp)
+	copy_long_to t0, sp, a0
+	sp_stack_epilogue a1
+	.option pop
+	ret
+.endm
+
+
+ /*
+ * a0 = addr to load from
+ * a1 = address offset
+ * a2 = value to be loaded
+ */
+gen_test_inst lh
+gen_test_inst lhu
+gen_test_inst lw
+gen_test_inst lwu
+gen_test_inst ld
+#ifdef __riscv_compressed
+gen_test_inst_c lw
+gen_test_inst_c ld
+gen_test_inst_load_c_sp ld
+#endif
+
+/*
+ * a0 = addr where to store value
+ * a1 = address offset
+ * a2 = value to be stored
+ */
+gen_test_inst sh
+gen_test_inst sw
+gen_test_inst sd
+#ifdef __riscv_compressed
+gen_test_inst_c sw
+gen_test_inst_c sd
+gen_test_inst_store_c_sp sd
+#endif
+
diff --git a/tools/testing/selftests/riscv/misaligned/misaligned.c b/tools/testing/selftests/riscv/misaligned/misaligned.c
new file mode 100644
index 000000000000..5caa8c1c50bd
--- /dev/null
+++ b/tools/testing/selftests/riscv/misaligned/misaligned.c
@@ -0,0 +1,254 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ *     Clément Léger <cleger@rivosinc.com>
+ */
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <linux/ptrace.h>
+#include "../../kselftest_harness.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <float.h>
+#include <errno.h>
+#include <math.h>
+#include <string.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <ucontext.h>
+
+#include <sys/prctl.h>
+
+#define stringify(s) __stringify(s)
+#define __stringify(s) #s
+
+#define VAL16	0x1234
+#define VAL32	0xDEADBEEF
+#define VAL64	0x45674321D00DF789
+
+#define VAL_float	78951.234375
+#define VAL_double	567890.512396965789589290
+
+static bool float_equal(float a, float b)
+{
+	float scaled_epsilon;
+	float difference = fabsf(a - b);
+
+	// Scale to the largest value.
+	a = fabsf(a);
+	b = fabsf(b);
+	if (a > b)
+		scaled_epsilon = FLT_EPSILON * a;
+	else
+		scaled_epsilon = FLT_EPSILON * b;
+
+	return difference <= scaled_epsilon;
+}
+
+static bool double_equal(double a, double b)
+{
+	double scaled_epsilon;
+	double difference = fabsf(a - b);
+
+	// Scale to the largest value.
+	a = fabs(a);
+	b = fabs(b);
+	if (a > b)
+		scaled_epsilon = DBL_EPSILON * a;
+	else
+		scaled_epsilon = DBL_EPSILON * b;
+
+	return difference <= scaled_epsilon;
+}
+
+#define fpu_load_proto(__inst, __type) \
+extern __type test_ ## __inst(unsigned long fp_reg, void *addr, unsigned long offset, __type value)
+
+fpu_load_proto(flw, float);
+fpu_load_proto(fld, double);
+fpu_load_proto(c_flw, float);
+fpu_load_proto(c_fld, double);
+fpu_load_proto(c_fldsp, double);
+
+#define fpu_store_proto(__inst, __type) \
+extern void test_ ## __inst(unsigned long fp_reg, void *addr, unsigned long offset, __type value)
+
+fpu_store_proto(fsw, float);
+fpu_store_proto(fsd, double);
+fpu_store_proto(c_fsw, float);
+fpu_store_proto(c_fsd, double);
+fpu_store_proto(c_fsdsp, double);
+
+#define gp_load_proto(__inst, __type) \
+extern __type test_ ## __inst(void *addr, unsigned long offset, __type value)
+
+gp_load_proto(lh, uint16_t);
+gp_load_proto(lhu, uint16_t);
+gp_load_proto(lw, uint32_t);
+gp_load_proto(lwu, uint32_t);
+gp_load_proto(ld, uint64_t);
+gp_load_proto(c_lw, uint32_t);
+gp_load_proto(c_ld, uint64_t);
+gp_load_proto(c_ldsp, uint64_t);
+
+#define gp_store_proto(__inst, __type) \
+extern void test_ ## __inst(void *addr, unsigned long offset, __type value)
+
+gp_store_proto(sh, uint16_t);
+gp_store_proto(sw, uint32_t);
+gp_store_proto(sd, uint64_t);
+gp_store_proto(c_sw, uint32_t);
+gp_store_proto(c_sd, uint64_t);
+gp_store_proto(c_sdsp, uint64_t);
+
+#define TEST_GP_LOAD(__inst, __type_size)					\
+TEST(gp_load_ ## __inst)							\
+{										\
+	int offset, ret;							\
+	uint8_t buf[16] __attribute__((aligned(16)));				\
+										\
+	ret = prctl(PR_SET_UNALIGN, PR_UNALIGN_NOPRINT);			\
+	ASSERT_EQ(ret, 0);							\
+										\
+	for (offset = 1; offset < __type_size/8; offset++) {			\
+		uint ## __type_size ## _t val = VAL ## __type_size;		\
+		uint ## __type_size ## _t *ptr = (uint ## __type_size ## _t *) (buf + offset); \
+		memcpy(ptr, &val, sizeof(val));					\
+		val = test_ ## __inst(ptr, offset, val);			\
+		EXPECT_EQ(VAL ## __type_size, val);				\
+	}									\
+}
+
+TEST_GP_LOAD(lh, 16);
+TEST_GP_LOAD(lhu, 16);
+TEST_GP_LOAD(lw, 32);
+TEST_GP_LOAD(lwu, 32);
+TEST_GP_LOAD(ld, 64);
+#ifdef __riscv_compressed
+TEST_GP_LOAD(c_lw, 32);
+TEST_GP_LOAD(c_ld, 64);
+TEST_GP_LOAD(c_ldsp, 64);
+#endif
+
+#define TEST_GP_STORE(__inst, __type_size)					\
+TEST(gp_load_ ## __inst)							\
+{										\
+	int offset, ret;							\
+	uint8_t buf[16] __attribute__((aligned(16)));				\
+										\
+	ret = prctl(PR_SET_UNALIGN, PR_UNALIGN_NOPRINT);			\
+	ASSERT_EQ(ret, 0);							\
+										\
+	for (offset = 1; offset < __type_size/8; offset++) {			\
+		uint ## __type_size ## _t val = VAL ## __type_size;		\
+		uint ## __type_size ## _t *ptr = (uint ## __type_size ## _t *) (buf + offset); \
+		memset(ptr, 0, sizeof(val));					\
+		test_ ## __inst(ptr, offset, val);				\
+		memcpy(&val, ptr, sizeof(val));					\
+		EXPECT_EQ(VAL ## __type_size, val);				\
+	}									\
+}
+TEST_GP_STORE(sh, 16);
+TEST_GP_STORE(sw, 32);
+TEST_GP_STORE(sd, 64);
+#ifdef __riscv_compressed
+TEST_GP_STORE(c_sw, 32);
+TEST_GP_STORE(c_sd, 64);
+TEST_GP_STORE(c_sdsp, 64);
+#endif
+
+#define __TEST_FPU_LOAD(__type, __inst, __reg_start, __reg_end)			\
+TEST(fpu_load_ ## __inst)							\
+{										\
+	int i, ret, offset, fp_reg;						\
+	uint8_t buf[16] __attribute__((aligned(16)));				\
+										\
+	ret = prctl(PR_SET_UNALIGN, PR_UNALIGN_NOPRINT);			\
+	ASSERT_EQ(ret, 0);							\
+										\
+	for (fp_reg = __reg_start; fp_reg < __reg_end; fp_reg++) {		\
+		for (offset = 1; offset < 4; offset++) {			\
+			void *load_addr = (buf + offset);			\
+			__type val = VAL_ ## __type ;				\
+										\
+			memcpy(load_addr, &val, sizeof(val));			\
+			val = test_ ## __inst(fp_reg, load_addr, offset, val);	\
+			EXPECT_TRUE(__type ##_equal(val, VAL_## __type));	\
+		}								\
+	}									\
+}
+#define TEST_FPU_LOAD(__type, __inst) \
+	__TEST_FPU_LOAD(__type, __inst, 0, 32)
+#define TEST_FPU_LOAD_COMPRESSED(__type, __inst) \
+	__TEST_FPU_LOAD(__type, __inst, 8, 16)
+
+TEST_FPU_LOAD(float, flw)
+TEST_FPU_LOAD(double, fld)
+#ifdef __riscv_compressed
+TEST_FPU_LOAD_COMPRESSED(double, c_fld)
+TEST_FPU_LOAD_COMPRESSED(double, c_fldsp)
+#endif
+
+#define __TEST_FPU_STORE(__type, __inst, __reg_start, __reg_end)		\
+TEST(fpu_store_ ## __inst)							\
+{										\
+	int i, ret, offset, fp_reg;						\
+	uint8_t buf[16] __attribute__((aligned(16)));				\
+										\
+	ret = prctl(PR_SET_UNALIGN, PR_UNALIGN_NOPRINT);			\
+	ASSERT_EQ(ret, 0);							\
+										\
+	for (fp_reg = __reg_start; fp_reg < __reg_end; fp_reg++) {		\
+		for (offset = 1; offset < 4; offset++) {			\
+										\
+			void *store_addr = (buf + offset);			\
+			__type val = VAL_ ## __type ;				\
+										\
+			test_ ## __inst(fp_reg, store_addr, offset, val);	\
+			memcpy(&val, store_addr, sizeof(val));			\
+			EXPECT_TRUE(__type ## _equal(val, VAL_## __type));	\
+		}								\
+	}									\
+}
+#define TEST_FPU_STORE(__type, __inst) \
+	__TEST_FPU_STORE(__type, __inst, 0, 32)
+#define TEST_FPU_STORE_COMPRESSED(__type, __inst) \
+	__TEST_FPU_STORE(__type, __inst, 8, 16)
+
+TEST_FPU_STORE(float, fsw)
+TEST_FPU_STORE(double, fsd)
+#ifdef __riscv_compressed
+TEST_FPU_STORE_COMPRESSED(double, c_fsd)
+TEST_FPU_STORE_COMPRESSED(double, c_fsdsp)
+#endif
+
+TEST_SIGNAL(gen_sigbus, SIGBUS)
+{
+	uint32_t *ptr;
+	uint8_t buf[16] __attribute__((aligned(16)));
+	int ret;
+
+	ret = prctl(PR_SET_UNALIGN, PR_UNALIGN_SIGBUS);
+	ASSERT_EQ(ret, 0);
+
+	ptr = (uint32_t *)(buf + 1);
+	*ptr = 0xDEADBEEFULL;
+}
+
+int main(int argc, char **argv)
+{
+	int ret, val;
+
+	ret = prctl(PR_GET_UNALIGN, &val);
+	if (ret == -1 && errno == EINVAL)
+		ksft_exit_skip("SKIP GET_UNALIGN_CTL not supported\n");
+
+	exit(test_harness_run(argc, argv));
+}
-- 
2.47.2

[PATCH v2 12/15] RISC-V: KVM: add SBI extension init()/deinit() functions

[Clément Léger]

The FWFT SBI extension will need to dynamically allocate memory and do
init time specific initialization. Add an init/deinit callbacks that
allows to do so.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/include/asm/kvm_vcpu_sbi.h |  9 ++++++++
 arch/riscv/kvm/vcpu.c                 |  2 ++
 arch/riscv/kvm/vcpu_sbi.c             | 30 +++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index 4ed6203cdd30..bcb90757b149 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -49,6 +49,14 @@ struct kvm_vcpu_sbi_extension {
 
 	/* Extension specific probe function */
 	unsigned long (*probe)(struct kvm_vcpu *vcpu);
+
+	/*
+	 * Init/deinit function called once during VCPU init/destroy. These
+	 * might be use if the SBI extensions need to allocate or do specific
+	 * init time only configuration.
+	 */
+	int (*init)(struct kvm_vcpu *vcpu);
+	void (*deinit)(struct kvm_vcpu *vcpu);
 };
 
 void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
@@ -69,6 +77,7 @@ const struct kvm_vcpu_sbi_extension *kvm_vcpu_sbi_find_ext(
 bool riscv_vcpu_supports_sbi_ext(struct kvm_vcpu *vcpu, int idx);
 int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);
 void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
 
 int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
 				   unsigned long *reg_val);
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 60d684c76c58..877bcc85c067 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -185,6 +185,8 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 {
+	kvm_riscv_vcpu_sbi_deinit(vcpu);
+
 	/* Cleanup VCPU AIA context */
 	kvm_riscv_vcpu_aia_deinit(vcpu);
 
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index d1c83a77735e..44f551143498 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -505,8 +505,38 @@ void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu)
 			continue;
 		}
 
+		if (!ext->default_disabled && ext->init &&
+		    ext->init(vcpu) != 0) {
+			    scontext->ext_status[idx] =
+				    KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
+			    continue;
+		}
+
 		scontext->ext_status[idx] = ext->default_disabled ?
 					KVM_RISCV_SBI_EXT_STATUS_DISABLED :
 					KVM_RISCV_SBI_EXT_STATUS_ENABLED;
 	}
 }
+
+void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
+	const struct kvm_riscv_sbi_extension_entry *entry;
+	const struct kvm_vcpu_sbi_extension *ext;
+	int idx, i;
+
+	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
+		entry = &sbi_ext[i];
+		ext = entry->ext_ptr;
+		idx = entry->ext_idx;
+
+		if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
+			continue;
+
+		if (scontext->ext_status[idx] == KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE ||
+		    !ext->deinit)
+			continue;
+
+		ext->deinit(vcpu);
+	}
+}
-- 
2.47.2

[PATCH v2 13/15] RISC-V: KVM: add SBI extension reset callback

[Clément Léger]

Currently, oonly the STA extension needed a reset function but that's
going to be the case for FWFT as well. Add a reset callback that can be
implemented by SBI extensions.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/include/asm/kvm_host.h     |  1 -
 arch/riscv/include/asm/kvm_vcpu_sbi.h |  2 ++
 arch/riscv/kvm/vcpu.c                 |  2 +-
 arch/riscv/kvm/vcpu_sbi.c             | 24 ++++++++++++++++++++++++
 arch/riscv/kvm/vcpu_sbi_sta.c         |  3 ++-
 5 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index cc33e35cd628..bb93d2995ea2 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -409,7 +409,6 @@ void __kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
 void kvm_riscv_vcpu_power_on(struct kvm_vcpu *vcpu);
 bool kvm_riscv_vcpu_stopped(struct kvm_vcpu *vcpu);
 
-void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu);
 void kvm_riscv_vcpu_record_steal_time(struct kvm_vcpu *vcpu);
 
 #endif /* __RISCV_KVM_HOST_H__ */
diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
index bcb90757b149..cb68b3a57c8f 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -57,6 +57,7 @@ struct kvm_vcpu_sbi_extension {
 	 */
 	int (*init)(struct kvm_vcpu *vcpu);
 	void (*deinit)(struct kvm_vcpu *vcpu);
+	void (*reset)(struct kvm_vcpu *vcpu);
 };
 
 void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
@@ -78,6 +79,7 @@ bool riscv_vcpu_supports_sbi_ext(struct kvm_vcpu *vcpu, int idx);
 int kvm_riscv_vcpu_sbi_ecall(struct kvm_vcpu *vcpu, struct kvm_run *run);
 void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu);
 void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu);
+void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu);
 
 int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu, unsigned long reg_num,
 				   unsigned long *reg_val);
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 877bcc85c067..542747e2c7f5 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -94,7 +94,7 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
 	vcpu->arch.hfence_tail = 0;
 	memset(vcpu->arch.hfence_queue, 0, sizeof(vcpu->arch.hfence_queue));
 
-	kvm_riscv_vcpu_sbi_sta_reset(vcpu);
+	kvm_riscv_vcpu_sbi_reset(vcpu);
 
 	/* Reset the guest CSRs for hotplug usecase */
 	if (loaded)
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 44f551143498..f81f06f82650 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -540,3 +540,27 @@ void kvm_riscv_vcpu_sbi_deinit(struct kvm_vcpu *vcpu)
 		ext->deinit(vcpu);
 	}
 }
+
+void kvm_riscv_vcpu_sbi_reset(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
+	const struct kvm_riscv_sbi_extension_entry *entry;
+	const struct kvm_vcpu_sbi_extension *ext;
+	int idx, i;
+
+	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
+		entry = &sbi_ext[i];
+		ext = entry->ext_ptr;
+		idx = entry->ext_idx;
+
+		if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
+			continue;
+
+		if (scontext->ext_status[idx] != KVM_RISCV_SBI_EXT_STATUS_ENABLED ||
+		    !ext->reset)
+			continue;
+
+		ext->reset(vcpu);
+	}
+}
+
diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
index 5f35427114c1..cc6cb7c8f0e4 100644
--- a/arch/riscv/kvm/vcpu_sbi_sta.c
+++ b/arch/riscv/kvm/vcpu_sbi_sta.c
@@ -16,7 +16,7 @@
 #include <asm/sbi.h>
 #include <asm/uaccess.h>
 
-void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu)
+static void kvm_riscv_vcpu_sbi_sta_reset(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.sta.shmem = INVALID_GPA;
 	vcpu->arch.sta.last_steal = 0;
@@ -156,6 +156,7 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {
 	.extid_end = SBI_EXT_STA,
 	.handler = kvm_sbi_ext_sta_handler,
 	.probe = kvm_sbi_ext_sta_probe,
+	.reset = kvm_riscv_vcpu_sbi_sta_reset,
 };
 
 int kvm_riscv_vcpu_get_reg_sbi_sta(struct kvm_vcpu *vcpu,
-- 
2.47.2

[PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

[Clément Léger]

Add basic infrastructure to support the FWFT extension in KVM.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 arch/riscv/include/asm/kvm_host.h          |   4 +
 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_sbi.c                  |   4 +
 arch/riscv/kvm/vcpu_sbi_fwft.c             | 187 +++++++++++++++++++++
 7 files changed, 235 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 bb93d2995ea2..c0db61ba691a 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>
 
@@ -281,6 +282,9 @@ 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 cb68b3a57c8f..ffd03fed0c06 100644
--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
@@ -98,6 +98,7 @@ 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_susp;
 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..5782517f6e08
--- /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) 2025 Rivos Inc.
+ *
+ * Authors:
+ *     Clément Léger <cleger@rivosinc.com>
+ */
+
+#ifndef __KVM_VCPU_RISCV_FWFT_H
+#define __KVM_VCPU_RISCV_FWFT_H
+
+#include <asm/sbi.h>
+
+struct kvm_sbi_fwft_config;
+struct kvm_vcpu;
+
+struct kvm_sbi_fwft_feature {
+	enum sbi_fwft_feature_t id;
+	bool (*supported)(struct kvm_vcpu *vcpu);
+	int (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
+	int (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);
+};
+
+struct kvm_sbi_fwft_config {
+	const struct kvm_sbi_fwft_feature *feature;
+	bool supported;
+	unsigned long flags;
+};
+
+/* FWFT data structure per vcpu */
+struct kvm_sbi_fwft {
+	struct kvm_sbi_fwft_config *configs;
+};
+
+#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
+
+#endif /* !__KVM_VCPU_RISCV_FWFT_H */
diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index f06bc5efcd79..fa6eee1caf41 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -202,6 +202,7 @@ enum KVM_RISCV_SBI_EXT_ID {
 	KVM_RISCV_SBI_EXT_DBCN,
 	KVM_RISCV_SBI_EXT_STA,
 	KVM_RISCV_SBI_EXT_SUSP,
+	KVM_RISCV_SBI_EXT_FWFT,
 	KVM_RISCV_SBI_EXT_MAX,
 };
 
diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
index 4e0bba91d284..06e2d52a9b88 100644
--- a/arch/riscv/kvm/Makefile
+++ b/arch/riscv/kvm/Makefile
@@ -26,6 +26,7 @@ kvm-y += vcpu_onereg.o
 kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
 kvm-y += vcpu_sbi.o
 kvm-y += vcpu_sbi_base.o
+kvm-y += vcpu_sbi_fwft.o
 kvm-y += vcpu_sbi_hsm.o
 kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
 kvm-y += vcpu_sbi_replace.o
diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index f81f06f82650..3b37deaed4e7 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
 		.ext_idx = KVM_RISCV_SBI_EXT_STA,
 		.ext_ptr = &vcpu_sbi_ext_sta,
 	},
+	{
+		.ext_idx = KVM_RISCV_SBI_EXT_FWFT,
+		.ext_ptr = &vcpu_sbi_ext_fwft,
+	},
 	{
 		.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
 		.ext_ptr = &vcpu_sbi_ext_experimental,
diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
new file mode 100644
index 000000000000..fe608bf16558
--- /dev/null
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025 Rivos Inc.
+ *
+ * Authors:
+ *     Clément Léger <cleger@rivosinc.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/kvm_host.h>
+#include <asm/cpufeature.h>
+#include <asm/sbi.h>
+#include <asm/kvm_vcpu_sbi.h>
+#include <asm/kvm_vcpu_sbi_fwft.h>
+
+static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
+	SBI_FWFT_MISALIGNED_EXC_DELEG,
+	SBI_FWFT_LANDING_PAD,
+	SBI_FWFT_SHADOW_STACK,
+	SBI_FWFT_DOUBLE_TRAP,
+	SBI_FWFT_PTE_AD_HW_UPDATING,
+	SBI_FWFT_POINTER_MASKING_PMLEN,
+};
+
+static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(kvm_fwft_defined_features); i++) {
+		if (kvm_fwft_defined_features[i] == feature)
+			return true;
+	}
+
+	return false;
+}
+
+static const struct kvm_sbi_fwft_feature features[] = {
+};
+
+static struct kvm_sbi_fwft_config *
+kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum sbi_fwft_feature_t feature)
+{
+	int i = 0;
+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+
+	for (i = 0; i < ARRAY_SIZE(features); i++) {
+		if (fwft->configs[i].feature->id == feature)
+			return &fwft->configs[i];
+	}
+
+	return NULL;
+}
+
+static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, unsigned long feature,
+				struct kvm_sbi_fwft_config **conf)
+{
+	struct kvm_sbi_fwft_config *tconf;
+
+	/* Feature are defined as 32 bits identifiers */
+	if (feature & ~(BIT_ULL(32) - 1))
+		return SBI_ERR_INVALID_PARAM;
+
+	tconf = kvm_sbi_fwft_get_config(vcpu, feature);
+	if (!tconf) {
+		if (kvm_fwft_is_defined_feature(feature))
+			return SBI_ERR_NOT_SUPPORTED;
+
+		return SBI_ERR_DENIED;
+	}
+
+	if (!tconf->supported)
+		return SBI_ERR_NOT_SUPPORTED;
+
+	*conf = tconf;
+
+	return SBI_SUCCESS;
+}
+
+static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, unsigned long feature,
+			    unsigned long value, unsigned long flags)
+{
+	int ret;
+	struct kvm_sbi_fwft_config *conf;
+
+	ret = kvm_fwft_get_feature(vcpu, feature, &conf);
+	if (ret)
+		return ret;
+
+	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_LOCKED;
+
+	conf->flags = flags;
+
+	return conf->feature->set(vcpu, conf, value);
+}
+
+static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
+			    unsigned long *value)
+{
+	int ret;
+	struct kvm_sbi_fwft_config *conf;
+
+	ret = kvm_fwft_get_feature(vcpu, feature, &conf);
+	if (ret)
+		return ret;
+
+	return conf->feature->get(vcpu, conf, value);
+}
+
+static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
+				    struct kvm_vcpu_sbi_return *retdata)
+{
+	int ret = 0;
+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+	unsigned long funcid = cp->a6;
+
+	switch (funcid) {
+	case SBI_EXT_FWFT_SET:
+		ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
+		break;
+	case SBI_EXT_FWFT_GET:
+		ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
+		break;
+	default:
+		ret = SBI_ERR_NOT_SUPPORTED;
+		break;
+	}
+
+	retdata->err_val = ret;
+
+	return 0;
+}
+
+static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
+{
+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+	const struct kvm_sbi_fwft_feature *feature;
+	struct kvm_sbi_fwft_config *conf;
+	int i;
+
+	fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct kvm_sbi_fwft_config),
+				GFP_KERNEL);
+	if (!fwft->configs)
+		return -ENOMEM;
+
+	for (i = 0; i < ARRAY_SIZE(features); i++) {
+		feature = &features[i];
+		conf = &fwft->configs[i];
+		if (feature->supported)
+			conf->supported = feature->supported(vcpu);
+		else
+			conf->supported = true;
+
+		conf->feature = feature;
+	}
+
+	return 0;
+}
+
+static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
+{
+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+
+	kfree(fwft->configs);
+}
+
+static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
+{
+	int i = 0;
+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
+
+	for (i = 0; i < ARRAY_SIZE(features); i++)
+		fwft->configs[i].flags = 0;
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
+	.extid_start = SBI_EXT_FWFT,
+	.extid_end = SBI_EXT_FWFT,
+	.handler = kvm_sbi_ext_fwft_handler,
+	.init = kvm_sbi_ext_fwft_init,
+	.deinit = kvm_sbi_ext_fwft_deinit,
+	.reset = kvm_sbi_ext_fwft_reset,
+};
-- 
2.47.2

[PATCH v2 15/15] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

[Clément Léger]

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@rivosinc.com>
---
 arch/riscv/kvm/vcpu.c          |  3 +++
 arch/riscv/kvm/vcpu_sbi_fwft.c | 39 ++++++++++++++++++++++++++++++++++
 2 files changed, 42 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 fe608bf16558..235a46d553d4 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 (1UL << EXC_LOAD_MISALIGNED | 1UL << EXC_STORE_MISALIGNED)
+
 static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
 	SBI_FWFT_MISALIGNED_EXC_DELEG,
 	SBI_FWFT_LANDING_PAD,
@@ -35,7 +37,44 @@ 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)
+{
+	if (!misaligned_traps_can_delegate())
+		return false;
+
+	return true;
+}
+
+static int 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 int 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;
+
+	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 *
-- 
2.47.2

Re: [PATCH v2 01/15] riscv: add Firmware Feature (FWFT) SBI extensions definitions

[Deepak Gupta]

On Mon, Feb 10, 2025 at 10:35:34PM +0100, Clément Léger wrote:
>The Firmware Features extension (FWFT) was added as part of the SBI 3.0
>specification. Add SBI definitions to use this extension.
>
>Signed-off-by: Clément Léger <cleger@rivosinc.com>
>Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
>Tested-by: Samuel Holland <samuel.holland@sifive.com>
>---
> arch/riscv/include/asm/sbi.h | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
>diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>index 3d250824178b..d373b5c08039 100644
>--- a/arch/riscv/include/asm/sbi.h
>+++ b/arch/riscv/include/asm/sbi.h
>@@ -35,6 +35,7 @@ enum sbi_ext_id {
> 	SBI_EXT_DBCN = 0x4442434E,
> 	SBI_EXT_STA = 0x535441,
> 	SBI_EXT_NACL = 0x4E41434C,
>+	SBI_EXT_FWFT = 0x46574654,
>
> 	/* Experimentals extensions must lie within this range */
> 	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
>@@ -402,6 +403,33 @@ enum sbi_ext_nacl_feature {
> #define SBI_NACL_SHMEM_SRET_X(__i)		((__riscv_xlen / 8) * (__i))
> #define SBI_NACL_SHMEM_SRET_X_LAST		31
>
>+/* SBI function IDs for FW feature extension */
>+#define SBI_EXT_FWFT_SET		0x0
>+#define SBI_EXT_FWFT_GET		0x1
>+
>+enum sbi_fwft_feature_t {
>+	SBI_FWFT_MISALIGNED_EXC_DELEG		= 0x0,
>+	SBI_FWFT_LANDING_PAD			= 0x1,
>+	SBI_FWFT_SHADOW_STACK			= 0x2,
>+	SBI_FWFT_DOUBLE_TRAP			= 0x3,
>+	SBI_FWFT_PTE_AD_HW_UPDATING		= 0x4,
>+	SBI_FWFT_POINTER_MASKING_PMLEN		= 0x5,
>+	SBI_FWFT_LOCAL_RESERVED_START		= 0x6,
>+	SBI_FWFT_LOCAL_RESERVED_END		= 0x3fffffff,
>+	SBI_FWFT_LOCAL_PLATFORM_START		= 0x40000000,
>+	SBI_FWFT_LOCAL_PLATFORM_END		= 0x7fffffff,
>+
>+	SBI_FWFT_GLOBAL_RESERVED_START		= 0x80000000,
>+	SBI_FWFT_GLOBAL_RESERVED_END		= 0xbfffffff,
>+	SBI_FWFT_GLOBAL_PLATFORM_START		= 0xc0000000,
>+	SBI_FWFT_GLOBAL_PLATFORM_END		= 0xffffffff,
>+};
>+
>+#define SBI_FWFT_PLATFORM_FEATURE_BIT		(1 << 30)
>+#define SBI_FWFT_GLOBAL_FEATURE_BIT		(1 << 31)
>+
>+#define SBI_FWFT_SET_FLAG_LOCK			(1 << 0)
>+
> /* SBI spec version fields */
> #define SBI_SPEC_VERSION_DEFAULT	0x1
> #define SBI_SPEC_VERSION_MAJOR_SHIFT	24
>@@ -419,6 +447,11 @@ enum sbi_ext_nacl_feature {
> #define SBI_ERR_ALREADY_STARTED -7
> #define SBI_ERR_ALREADY_STOPPED -8
> #define SBI_ERR_NO_SHMEM	-9
>+#define SBI_ERR_INVALID_STATE	-10
>+#define SBI_ERR_BAD_RANGE	-11
>+#define SBI_ERR_TIMEOUT		-12

nit: Space mis-aligned(^)	^

otherwise
Reviewed-by: Deepak Gupta <debug@rivosinc.com>

>+#define SBI_ERR_IO		-13
>+#define SBI_ERR_DENIED_LOCKED	-14
>
> extern unsigned long sbi_spec_version;
> struct sbiret {
>-- 
>2.47.2
>
>

Re: [PATCH v2 01/15] riscv: add Firmware Feature (FWFT) SBI extensions definitions

[Samuel Holland]

Hi Deepak,

On 2025-02-10 10:06 PM, Deepak Gupta wrote:
> On Mon, Feb 10, 2025 at 10:35:34PM +0100, Clément Léger wrote:
>> The Firmware Features extension (FWFT) was added as part of the SBI 3.0
>> specification. Add SBI definitions to use this extension.
>>
>> Signed-off-by: Clément Léger <cleger@rivosinc.com>
>> Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
>> Tested-by: Samuel Holland <samuel.holland@sifive.com>
>> ---
>> arch/riscv/include/asm/sbi.h | 33 +++++++++++++++++++++++++++++++++
>> 1 file changed, 33 insertions(+)
>>
>> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>> index 3d250824178b..d373b5c08039 100644
>> --- a/arch/riscv/include/asm/sbi.h
>> +++ b/arch/riscv/include/asm/sbi.h
>> @@ -35,6 +35,7 @@ enum sbi_ext_id {
>>     SBI_EXT_DBCN = 0x4442434E,
>>     SBI_EXT_STA = 0x535441,
>>     SBI_EXT_NACL = 0x4E41434C,
>> +    SBI_EXT_FWFT = 0x46574654,
>>
>>     /* Experimentals extensions must lie within this range */
>>     SBI_EXT_EXPERIMENTAL_START = 0x08000000,
>> @@ -402,6 +403,33 @@ enum sbi_ext_nacl_feature {
>> #define SBI_NACL_SHMEM_SRET_X(__i)        ((__riscv_xlen / 8) * (__i))
>> #define SBI_NACL_SHMEM_SRET_X_LAST        31
>>
>> +/* SBI function IDs for FW feature extension */
>> +#define SBI_EXT_FWFT_SET        0x0
>> +#define SBI_EXT_FWFT_GET        0x1
>> +
>> +enum sbi_fwft_feature_t {
>> +    SBI_FWFT_MISALIGNED_EXC_DELEG        = 0x0,
>> +    SBI_FWFT_LANDING_PAD            = 0x1,
>> +    SBI_FWFT_SHADOW_STACK            = 0x2,
>> +    SBI_FWFT_DOUBLE_TRAP            = 0x3,
>> +    SBI_FWFT_PTE_AD_HW_UPDATING        = 0x4,
>> +    SBI_FWFT_POINTER_MASKING_PMLEN        = 0x5,
>> +    SBI_FWFT_LOCAL_RESERVED_START        = 0x6,
>> +    SBI_FWFT_LOCAL_RESERVED_END        = 0x3fffffff,
>> +    SBI_FWFT_LOCAL_PLATFORM_START        = 0x40000000,
>> +    SBI_FWFT_LOCAL_PLATFORM_END        = 0x7fffffff,
>> +
>> +    SBI_FWFT_GLOBAL_RESERVED_START        = 0x80000000,
>> +    SBI_FWFT_GLOBAL_RESERVED_END        = 0xbfffffff,
>> +    SBI_FWFT_GLOBAL_PLATFORM_START        = 0xc0000000,
>> +    SBI_FWFT_GLOBAL_PLATFORM_END        = 0xffffffff,
>> +};
>> +
>> +#define SBI_FWFT_PLATFORM_FEATURE_BIT        (1 << 30)
>> +#define SBI_FWFT_GLOBAL_FEATURE_BIT        (1 << 31)
>> +
>> +#define SBI_FWFT_SET_FLAG_LOCK            (1 << 0)
>> +
>> /* SBI spec version fields */
>> #define SBI_SPEC_VERSION_DEFAULT    0x1
>> #define SBI_SPEC_VERSION_MAJOR_SHIFT    24
>> @@ -419,6 +447,11 @@ enum sbi_ext_nacl_feature {
>> #define SBI_ERR_ALREADY_STARTED -7
>> #define SBI_ERR_ALREADY_STOPPED -8
>> #define SBI_ERR_NO_SHMEM    -9
>> +#define SBI_ERR_INVALID_STATE    -10
>> +#define SBI_ERR_BAD_RANGE    -11
>> +#define SBI_ERR_TIMEOUT        -12
> 
> nit: Space mis-aligned(^)    ^

The alignment is correct when the patch is applied. It only looks wrong in the
patch because the "+" from the unified diff format causes an overflow to the
next tab stop.

Regards,
Samuel

> otherwise
> Reviewed-by: Deepak Gupta <debug@rivosinc.com>
> 
>> +#define SBI_ERR_IO        -13
>> +#define SBI_ERR_DENIED_LOCKED    -14
>>
>> extern unsigned long sbi_spec_version;
>> struct sbiret {
>> -- 
>> 2.47.2
>>
>>

Re: [PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

[Deepak Gupta]

On Mon, Feb 10, 2025 at 10:35:47PM +0100, Clément Léger wrote:
>Add basic infrastructure to support the FWFT extension in KVM.
>
>Signed-off-by: Clément Léger <cleger@rivosinc.com>
>---
> arch/riscv/include/asm/kvm_host.h          |   4 +
> 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_sbi.c                  |   4 +
> arch/riscv/kvm/vcpu_sbi_fwft.c             | 187 +++++++++++++++++++++
> 7 files changed, 235 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 bb93d2995ea2..c0db61ba691a 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>
>
>@@ -281,6 +282,9 @@ 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 cb68b3a57c8f..ffd03fed0c06 100644
>--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
>+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>@@ -98,6 +98,7 @@ 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_susp;
> 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..5782517f6e08
>--- /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) 2025 Rivos Inc.
>+ *
>+ * Authors:
>+ *     Clément Léger <cleger@rivosinc.com>
>+ */
>+
>+#ifndef __KVM_VCPU_RISCV_FWFT_H
>+#define __KVM_VCPU_RISCV_FWFT_H
>+
>+#include <asm/sbi.h>
>+
>+struct kvm_sbi_fwft_config;
>+struct kvm_vcpu;
>+
>+struct kvm_sbi_fwft_feature {
>+	enum sbi_fwft_feature_t id;
>+	bool (*supported)(struct kvm_vcpu *vcpu);
>+	int (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
>+	int (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);
>+};
>+
>+struct kvm_sbi_fwft_config {
>+	const struct kvm_sbi_fwft_feature *feature;
>+	bool supported;
>+	unsigned long flags;
>+};
>+
>+/* FWFT data structure per vcpu */
>+struct kvm_sbi_fwft {
>+	struct kvm_sbi_fwft_config *configs;
>+};
>+
>+#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
>+
>+#endif /* !__KVM_VCPU_RISCV_FWFT_H */
>diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
>index f06bc5efcd79..fa6eee1caf41 100644
>--- a/arch/riscv/include/uapi/asm/kvm.h
>+++ b/arch/riscv/include/uapi/asm/kvm.h
>@@ -202,6 +202,7 @@ enum KVM_RISCV_SBI_EXT_ID {
> 	KVM_RISCV_SBI_EXT_DBCN,
> 	KVM_RISCV_SBI_EXT_STA,
> 	KVM_RISCV_SBI_EXT_SUSP,
>+	KVM_RISCV_SBI_EXT_FWFT,
> 	KVM_RISCV_SBI_EXT_MAX,
> };
>
>diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
>index 4e0bba91d284..06e2d52a9b88 100644
>--- a/arch/riscv/kvm/Makefile
>+++ b/arch/riscv/kvm/Makefile
>@@ -26,6 +26,7 @@ kvm-y += vcpu_onereg.o
> kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
> kvm-y += vcpu_sbi.o
> kvm-y += vcpu_sbi_base.o
>+kvm-y += vcpu_sbi_fwft.o
> kvm-y += vcpu_sbi_hsm.o
> kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
> kvm-y += vcpu_sbi_replace.o
>diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
>index f81f06f82650..3b37deaed4e7 100644
>--- a/arch/riscv/kvm/vcpu_sbi.c
>+++ b/arch/riscv/kvm/vcpu_sbi.c
>@@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
> 		.ext_idx = KVM_RISCV_SBI_EXT_STA,
> 		.ext_ptr = &vcpu_sbi_ext_sta,
> 	},
>+	{
>+		.ext_idx = KVM_RISCV_SBI_EXT_FWFT,
>+		.ext_ptr = &vcpu_sbi_ext_fwft,
>+	},
> 	{
> 		.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
> 		.ext_ptr = &vcpu_sbi_ext_experimental,
>diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
>new file mode 100644
>index 000000000000..fe608bf16558
>--- /dev/null
>+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
>@@ -0,0 +1,187 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/*
>+ * Copyright (c) 2025 Rivos Inc.
>+ *
>+ * Authors:
>+ *     Clément Léger <cleger@rivosinc.com>
>+ */
>+
>+#include <linux/errno.h>
>+#include <linux/err.h>
>+#include <linux/kvm_host.h>
>+#include <asm/cpufeature.h>
>+#include <asm/sbi.h>
>+#include <asm/kvm_vcpu_sbi.h>
>+#include <asm/kvm_vcpu_sbi_fwft.h>
>+
>+static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
>+	SBI_FWFT_MISALIGNED_EXC_DELEG,
>+	SBI_FWFT_LANDING_PAD,
>+	SBI_FWFT_SHADOW_STACK,
>+	SBI_FWFT_DOUBLE_TRAP,
>+	SBI_FWFT_PTE_AD_HW_UPDATING,
>+	SBI_FWFT_POINTER_MASKING_PMLEN,
>+};
>+
>+static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
>+{
>+	int i;
>+
>+	for (i = 0; i < ARRAY_SIZE(kvm_fwft_defined_features); i++) {
>+		if (kvm_fwft_defined_features[i] == feature)
>+			return true;
>+	}
>+
>+	return false;
>+}
>+
>+static const struct kvm_sbi_fwft_feature features[] = {
>+};
>+
>+static struct kvm_sbi_fwft_config *
>+kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum sbi_fwft_feature_t feature)
>+{
>+	int i = 0;
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+
>+	for (i = 0; i < ARRAY_SIZE(features); i++) {
>+		if (fwft->configs[i].feature->id == feature)
>+			return &fwft->configs[i];
>+	}
>+
>+	return NULL;
>+}
>+
>+static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, unsigned long feature,
>+				struct kvm_sbi_fwft_config **conf)
>+{
>+	struct kvm_sbi_fwft_config *tconf;
>+
>+	/* Feature are defined as 32 bits identifiers */
>+	if (feature & ~(BIT_ULL(32) - 1))
>+		return SBI_ERR_INVALID_PARAM;
>+
>+	tconf = kvm_sbi_fwft_get_config(vcpu, feature);
>+	if (!tconf) {
>+		if (kvm_fwft_is_defined_feature(feature))
>+			return SBI_ERR_NOT_SUPPORTED;
>+
>+		return SBI_ERR_DENIED;
>+	}
>+
>+	if (!tconf->supported)
>+		return SBI_ERR_NOT_SUPPORTED;
>+
>+	*conf = tconf;
>+
>+	return SBI_SUCCESS;
>+}
>+
>+static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, unsigned long feature,
>+			    unsigned long value, unsigned long flags)
>+{
>+	int ret;
>+	struct kvm_sbi_fwft_config *conf;
>+
>+	ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>+	if (ret)
>+		return ret;
>+
>+	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_LOCKED;
>+
>+	conf->flags = flags;
>+
>+	return conf->feature->set(vcpu, conf, value);
>+}
>+
>+static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
>+			    unsigned long *value)
>+{
>+	int ret;
>+	struct kvm_sbi_fwft_config *conf;
>+
>+	ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>+	if (ret)
>+		return ret;
>+
>+	return conf->feature->get(vcpu, conf, value);
>+}
>+
>+static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
>+				    struct kvm_vcpu_sbi_return *retdata)
>+{
>+	int ret = 0;
>+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
>+	unsigned long funcid = cp->a6;
>+
>+	switch (funcid) {
>+	case SBI_EXT_FWFT_SET:
>+		ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
>+		break;
>+	case SBI_EXT_FWFT_GET:
>+		ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
>+		break;
>+	default:
>+		ret = SBI_ERR_NOT_SUPPORTED;
>+		break;
>+	}
>+
>+	retdata->err_val = ret;
>+
>+	return 0;
>+}
>+
>+static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
>+{
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+	const struct kvm_sbi_fwft_feature *feature;
>+	struct kvm_sbi_fwft_config *conf;
>+	int i;
>+
>+	fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct kvm_sbi_fwft_config),
>+				GFP_KERNEL);
nit:

I understand that in next patch you grow the static array`features`. But in this patch
`ARRAY_SIZE(features)` evaluates to 0, thus kcalloc will be returning a pointer
to some slab block (IIRC, kcalloc will not return NULL if size eventually evals to 0)

This probably won't result in some bad stuff. But still there is a pointer in
fwft->configs which is pointing to some random stuff if `features` turns out to be
empty.

Let me know if I got that right or missing something.

>+	if (!fwft->configs)
>+		return -ENOMEM;
>+
>+	for (i = 0; i < ARRAY_SIZE(features); i++) {
>+		feature = &features[i];
>+		conf = &fwft->configs[i];
>+		if (feature->supported)
>+			conf->supported = feature->supported(vcpu);
>+		else
>+			conf->supported = true;
>+
>+		conf->feature = feature;
>+	}
>+
>+	return 0;
>+}
>+
>+static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
>+{
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+
>+	kfree(fwft->configs);
>+}
>+
>+static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
>+{
>+	int i = 0;
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+
>+	for (i = 0; i < ARRAY_SIZE(features); i++)
>+		fwft->configs[i].flags = 0;
>+}
>+
>+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
>+	.extid_start = SBI_EXT_FWFT,
>+	.extid_end = SBI_EXT_FWFT,
>+	.handler = kvm_sbi_ext_fwft_handler,
>+	.init = kvm_sbi_ext_fwft_init,
>+	.deinit = kvm_sbi_ext_fwft_deinit,
>+	.reset = kvm_sbi_ext_fwft_reset,
>+};
>-- 
>2.47.2
>
>

Re: [PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

[Deepak Gupta]

On Mon, Feb 10, 2025 at 10:35:47PM +0100, Clément Léger wrote:
>Add basic infrastructure to support the FWFT extension in KVM.
>
>Signed-off-by: Clément Léger <cleger@rivosinc.com>
>---
> arch/riscv/include/asm/kvm_host.h          |   4 +
> 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_sbi.c                  |   4 +
> arch/riscv/kvm/vcpu_sbi_fwft.c             | 187 +++++++++++++++++++++
> 7 files changed, 235 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 bb93d2995ea2..c0db61ba691a 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>
>
>@@ -281,6 +282,9 @@ 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 cb68b3a57c8f..ffd03fed0c06 100644
>--- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
>+++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>@@ -98,6 +98,7 @@ 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_susp;
> 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..5782517f6e08
>--- /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) 2025 Rivos Inc.
>+ *
>+ * Authors:
>+ *     Clément Léger <cleger@rivosinc.com>
>+ */
>+
>+#ifndef __KVM_VCPU_RISCV_FWFT_H
>+#define __KVM_VCPU_RISCV_FWFT_H
>+
>+#include <asm/sbi.h>
>+
>+struct kvm_sbi_fwft_config;
>+struct kvm_vcpu;
>+


Can we add some comments here for future fwft providers along below lines?

Reason being, patch defaults to `conf->supported = true` if `supported` fn
pointer in `kvm_sbi_fwft_feature` was NULL. Although `kvm_sbi_fwft_set/get`
does get/set fn pointers (it would happen even if `supported` fn pointer
was NULL).

>+struct kvm_sbi_fwft_feature {
>+	enum sbi_fwft_feature_t id;
	/* If function not provided, KVM will default assume to be true */
>+	bool (*supported)(struct kvm_vcpu *vcpu);
	/* Must always provide function pointers for get/set */
>+	int (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long value);
>+	int (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config *conf, unsigned long *value);


>+};
>+
>+struct kvm_sbi_fwft_config {
>+	const struct kvm_sbi_fwft_feature *feature;
>+	bool supported;
>+	unsigned long flags;
>+};
>+
>+/* FWFT data structure per vcpu */
>+struct kvm_sbi_fwft {
>+	struct kvm_sbi_fwft_config *configs;
>+};
>+
>+#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
>+
>+#endif /* !__KVM_VCPU_RISCV_FWFT_H */
>diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
>index f06bc5efcd79..fa6eee1caf41 100644
>--- a/arch/riscv/include/uapi/asm/kvm.h
>+++ b/arch/riscv/include/uapi/asm/kvm.h
>@@ -202,6 +202,7 @@ enum KVM_RISCV_SBI_EXT_ID {
> 	KVM_RISCV_SBI_EXT_DBCN,
> 	KVM_RISCV_SBI_EXT_STA,
> 	KVM_RISCV_SBI_EXT_SUSP,
>+	KVM_RISCV_SBI_EXT_FWFT,
> 	KVM_RISCV_SBI_EXT_MAX,
> };
>
>diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
>index 4e0bba91d284..06e2d52a9b88 100644
>--- a/arch/riscv/kvm/Makefile
>+++ b/arch/riscv/kvm/Makefile
>@@ -26,6 +26,7 @@ kvm-y += vcpu_onereg.o
> kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
> kvm-y += vcpu_sbi.o
> kvm-y += vcpu_sbi_base.o
>+kvm-y += vcpu_sbi_fwft.o
> kvm-y += vcpu_sbi_hsm.o
> kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
> kvm-y += vcpu_sbi_replace.o
>diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
>index f81f06f82650..3b37deaed4e7 100644
>--- a/arch/riscv/kvm/vcpu_sbi.c
>+++ b/arch/riscv/kvm/vcpu_sbi.c
>@@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
> 		.ext_idx = KVM_RISCV_SBI_EXT_STA,
> 		.ext_ptr = &vcpu_sbi_ext_sta,
> 	},
>+	{
>+		.ext_idx = KVM_RISCV_SBI_EXT_FWFT,
>+		.ext_ptr = &vcpu_sbi_ext_fwft,
>+	},
> 	{
> 		.ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
> 		.ext_ptr = &vcpu_sbi_ext_experimental,
>diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/vcpu_sbi_fwft.c
>new file mode 100644
>index 000000000000..fe608bf16558
>--- /dev/null
>+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
>@@ -0,0 +1,187 @@
>+// SPDX-License-Identifier: GPL-2.0
>+/*
>+ * Copyright (c) 2025 Rivos Inc.
>+ *
>+ * Authors:
>+ *     Clément Léger <cleger@rivosinc.com>
>+ */
>+
>+#include <linux/errno.h>
>+#include <linux/err.h>
>+#include <linux/kvm_host.h>
>+#include <asm/cpufeature.h>
>+#include <asm/sbi.h>
>+#include <asm/kvm_vcpu_sbi.h>
>+#include <asm/kvm_vcpu_sbi_fwft.h>
>+
>+static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
>+	SBI_FWFT_MISALIGNED_EXC_DELEG,
>+	SBI_FWFT_LANDING_PAD,
>+	SBI_FWFT_SHADOW_STACK,
>+	SBI_FWFT_DOUBLE_TRAP,
>+	SBI_FWFT_PTE_AD_HW_UPDATING,
>+	SBI_FWFT_POINTER_MASKING_PMLEN,
>+};
>+
>+static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
>+{
>+	int i;
>+
>+	for (i = 0; i < ARRAY_SIZE(kvm_fwft_defined_features); i++) {
>+		if (kvm_fwft_defined_features[i] == feature)
>+			return true;
>+	}
>+
>+	return false;
>+}
>+
>+static const struct kvm_sbi_fwft_feature features[] = {
>+};
>+
>+static struct kvm_sbi_fwft_config *
>+kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum sbi_fwft_feature_t feature)
>+{
>+	int i = 0;
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+
>+	for (i = 0; i < ARRAY_SIZE(features); i++) {
>+		if (fwft->configs[i].feature->id == feature)
>+			return &fwft->configs[i];
>+	}
>+
>+	return NULL;
>+}
>+
>+static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, unsigned long feature,
>+				struct kvm_sbi_fwft_config **conf)
>+{
>+	struct kvm_sbi_fwft_config *tconf;
>+
>+	/* Feature are defined as 32 bits identifiers */
>+	if (feature & ~(BIT_ULL(32) - 1))
>+		return SBI_ERR_INVALID_PARAM;
>+
>+	tconf = kvm_sbi_fwft_get_config(vcpu, feature);
>+	if (!tconf) {
>+		if (kvm_fwft_is_defined_feature(feature))
>+			return SBI_ERR_NOT_SUPPORTED;
>+
>+		return SBI_ERR_DENIED;
>+	}
>+
>+	if (!tconf->supported)
>+		return SBI_ERR_NOT_SUPPORTED;
>+
>+	*conf = tconf;
>+
>+	return SBI_SUCCESS;
>+}
>+
>+static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, unsigned long feature,
>+			    unsigned long value, unsigned long flags)
>+{
>+	int ret;
>+	struct kvm_sbi_fwft_config *conf;
>+
>+	ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>+	if (ret)
>+		return ret;
>+
>+	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_LOCKED;
>+
>+	conf->flags = flags;
>+
>+	return conf->feature->set(vcpu, conf, value);
>+}
>+
>+static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long feature,
>+			    unsigned long *value)
>+{
>+	int ret;
>+	struct kvm_sbi_fwft_config *conf;
>+
>+	ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>+	if (ret)
>+		return ret;
>+
>+	return conf->feature->get(vcpu, conf, value);
>+}
>+
>+static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
>+				    struct kvm_vcpu_sbi_return *retdata)
>+{
>+	int ret = 0;
>+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
>+	unsigned long funcid = cp->a6;
>+
>+	switch (funcid) {
>+	case SBI_EXT_FWFT_SET:
>+		ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
>+		break;
>+	case SBI_EXT_FWFT_GET:
>+		ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
>+		break;
>+	default:
>+		ret = SBI_ERR_NOT_SUPPORTED;
>+		break;
>+	}
>+
>+	retdata->err_val = ret;
>+
>+	return 0;
>+}
>+
>+static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
>+{
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+	const struct kvm_sbi_fwft_feature *feature;
>+	struct kvm_sbi_fwft_config *conf;
>+	int i;
>+
>+	fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct kvm_sbi_fwft_config),
>+				GFP_KERNEL);
>+	if (!fwft->configs)
>+		return -ENOMEM;
>+
>+	for (i = 0; i < ARRAY_SIZE(features); i++) {
>+		feature = &features[i];
>+		conf = &fwft->configs[i];
>+		if (feature->supported)
>+			conf->supported = feature->supported(vcpu);
>+		else
>+			conf->supported = true;
>+
>+		conf->feature = feature;
>+	}
>+
>+	return 0;
>+}
>+
>+static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
>+{
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+
>+	kfree(fwft->configs);
>+}
>+
>+static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
>+{
>+	int i = 0;
>+	struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>+
>+	for (i = 0; i < ARRAY_SIZE(features); i++)
>+		fwft->configs[i].flags = 0;
>+}
>+
>+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
>+	.extid_start = SBI_EXT_FWFT,
>+	.extid_end = SBI_EXT_FWFT,
>+	.handler = kvm_sbi_ext_fwft_handler,
>+	.init = kvm_sbi_ext_fwft_init,
>+	.deinit = kvm_sbi_ext_fwft_deinit,
>+	.reset = kvm_sbi_ext_fwft_reset,
>+};
>-- 
>2.47.2
>
>

Re: [PATCH v2 15/15] RISC-V: KVM: add support for SBI_FWFT_MISALIGNED_DELEG

[Deepak Gupta]

On Mon, Feb 10, 2025 at 10:35:48PM +0100, 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@rivosinc.com>

Reviewed-by: Deepak Gupta <debug@rivosinc.com>

>---
> arch/riscv/kvm/vcpu.c          |  3 +++
> arch/riscv/kvm/vcpu_sbi_fwft.c | 39 ++++++++++++++++++++++++++++++++++
> 2 files changed, 42 insertions(+)
>
>diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c

Re: [PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

[Clément Léger]

On 11/02/2025 06:43, Deepak Gupta wrote:
>> +static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long
>> feature,
>> +                unsigned long *value)
>> +{
>> +    int ret;
>> +    struct kvm_sbi_fwft_config *conf;
>> +
>> +    ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>> +    if (ret)
>> +        return ret;
>> +
>> +    return conf->feature->get(vcpu, conf, value);
>> +}
>> +
>> +static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct
>> kvm_run *run,
>> +                    struct kvm_vcpu_sbi_return *retdata)
>> +{
>> +    int ret = 0;
>> +    struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
>> +    unsigned long funcid = cp->a6;
>> +
>> +    switch (funcid) {
>> +    case SBI_EXT_FWFT_SET:
>> +        ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
>> +        break;
>> +    case SBI_EXT_FWFT_GET:
>> +        ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
>> +        break;
>> +    default:
>> +        ret = SBI_ERR_NOT_SUPPORTED;
>> +        break;
>> +    }
>> +
>> +    retdata->err_val = ret;
>> +
>> +    return 0;
>> +}
>> +
>> +static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
>> +{
>> +    struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>> +    const struct kvm_sbi_fwft_feature *feature;
>> +    struct kvm_sbi_fwft_config *conf;
>> +    int i;
>> +
>> +    fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct
>> kvm_sbi_fwft_config),
>> +                GFP_KERNEL);
> nit:
> 
> I understand that in next patch you grow the static array`features`. But
> in this patch
> `ARRAY_SIZE(features)` evaluates to 0, thus kcalloc will be returning a
> pointer
> to some slab block (IIRC, kcalloc will not return NULL if size
> eventually evals to 0)
> 
> This probably won't result in some bad stuff. But still there is a
> pointer in
> fwft->configs which is pointing to some random stuff if `features` turns
> out to be
> empty.
> 
> Let me know if I got that right or missing something.

So I actually searched into the kmalloc code to see what hapopens with a
zero size allocation and it actually return ZERO_SIZE_PTR:

/*
 * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
 *
 * Dereferencing ZERO_SIZE_PTR will lead to a distinct access fault.
 *
 * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL
can.
 * Both make kfree a no-op.
 */

Which seems like it's not really random and will fault if accessed. I
think that's enough for that commit (which will be bisectable if needed
then).

Clément

Re: [PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

[Deepak Gupta]

On Tue, Feb 11, 2025 at 11:31:28AM +0100, Clément Léger wrote:
>
>
>On 11/02/2025 06:43, Deepak Gupta wrote:
>>> +static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long
>>> feature,
>>> +                unsigned long *value)
>>> +{
>>> +    int ret;
>>> +    struct kvm_sbi_fwft_config *conf;
>>> +
>>> +    ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>>> +    if (ret)
>>> +        return ret;
>>> +
>>> +    return conf->feature->get(vcpu, conf, value);
>>> +}
>>> +
>>> +static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct
>>> kvm_run *run,
>>> +                    struct kvm_vcpu_sbi_return *retdata)
>>> +{
>>> +    int ret = 0;
>>> +    struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
>>> +    unsigned long funcid = cp->a6;
>>> +
>>> +    switch (funcid) {
>>> +    case SBI_EXT_FWFT_SET:
>>> +        ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
>>> +        break;
>>> +    case SBI_EXT_FWFT_GET:
>>> +        ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
>>> +        break;
>>> +    default:
>>> +        ret = SBI_ERR_NOT_SUPPORTED;
>>> +        break;
>>> +    }
>>> +
>>> +    retdata->err_val = ret;
>>> +
>>> +    return 0;
>>> +}
>>> +
>>> +static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
>>> +{
>>> +    struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>>> +    const struct kvm_sbi_fwft_feature *feature;
>>> +    struct kvm_sbi_fwft_config *conf;
>>> +    int i;
>>> +
>>> +    fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct
>>> kvm_sbi_fwft_config),
>>> +                GFP_KERNEL);
>> nit:
>>
>> I understand that in next patch you grow the static array`features`. But
>> in this patch
>> `ARRAY_SIZE(features)` evaluates to 0, thus kcalloc will be returning a
>> pointer
>> to some slab block (IIRC, kcalloc will not return NULL if size
>> eventually evals to 0)
>>
>> This probably won't result in some bad stuff. But still there is a
>> pointer in
>> fwft->configs which is pointing to some random stuff if `features` turns
>> out to be
>> empty.
>>
>> Let me know if I got that right or missing something.
>
>So I actually searched into the kmalloc code to see what hapopens with a
>zero size allocation and it actually return ZERO_SIZE_PTR:
>
>/*
> * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
> *
> * Dereferencing ZERO_SIZE_PTR will lead to a distinct access fault.
> *
> * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL
>can.
> * Both make kfree a no-op.
> */
>
>Which seems like it's not really random and will fault if accessed. I
>think that's enough for that commit (which will be bisectable if needed
>then).
>

Awesome. Thanks for looking into it.

>Clément

Re: [PATCH v2 14/15] RISC-V: KVM: add support for FWFT SBI extension

[Clément Léger]

On 11/02/2025 06:57, Deepak Gupta wrote:
> On Mon, Feb 10, 2025 at 10:35:47PM +0100, Clément Léger wrote:
>> Add basic infrastructure to support the FWFT extension in KVM.
>>
>> Signed-off-by: Clément Léger <cleger@rivosinc.com>
>> ---
>> arch/riscv/include/asm/kvm_host.h          |   4 +
>> 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_sbi.c                  |   4 +
>> arch/riscv/kvm/vcpu_sbi_fwft.c             | 187 +++++++++++++++++++++
>> 7 files changed, 235 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 bb93d2995ea2..c0db61ba691a 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>
>>
>> @@ -281,6 +282,9 @@ 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 cb68b3a57c8f..ffd03fed0c06 100644
>> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
>> @@ -98,6 +98,7 @@ 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_susp;
>> 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..5782517f6e08
>> --- /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) 2025 Rivos Inc.
>> + *
>> + * Authors:
>> + *     Clément Léger <cleger@rivosinc.com>
>> + */
>> +
>> +#ifndef __KVM_VCPU_RISCV_FWFT_H
>> +#define __KVM_VCPU_RISCV_FWFT_H
>> +
>> +#include <asm/sbi.h>
>> +
>> +struct kvm_sbi_fwft_config;
>> +struct kvm_vcpu;
>> +
> 
> 
> Can we add some comments here for future fwft providers along below lines?
> 
> Reason being, patch defaults to `conf->supported = true` if `supported` fn
> pointer in `kvm_sbi_fwft_feature` was NULL. Although `kvm_sbi_fwft_set/get`
> does get/set fn pointers (it would happen even if `supported` fn pointer
> was NULL).

Yes sure, I'll add some kernel doc comments.

Thanks,

Clément

> 
>> +struct kvm_sbi_fwft_feature {
>> +    enum sbi_fwft_feature_t id;
>     /* If function not provided, KVM will default assume to be true */
>> +    bool (*supported)(struct kvm_vcpu *vcpu);
>     /* Must always provide function pointers for get/set */
>> +    int (*set)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config
>> *conf, unsigned long value);
>> +    int (*get)(struct kvm_vcpu *vcpu, struct kvm_sbi_fwft_config
>> *conf, unsigned long *value);
> 
> 
>> +};
>> +
>> +struct kvm_sbi_fwft_config {
>> +    const struct kvm_sbi_fwft_feature *feature;
>> +    bool supported;
>> +    unsigned long flags;
>> +};
>> +
>> +/* FWFT data structure per vcpu */
>> +struct kvm_sbi_fwft {
>> +    struct kvm_sbi_fwft_config *configs;
>> +};
>> +
>> +#define vcpu_to_fwft(vcpu) (&(vcpu)->arch.fwft_context)
>> +
>> +#endif /* !__KVM_VCPU_RISCV_FWFT_H */
>> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/
>> uapi/asm/kvm.h
>> index f06bc5efcd79..fa6eee1caf41 100644
>> --- a/arch/riscv/include/uapi/asm/kvm.h
>> +++ b/arch/riscv/include/uapi/asm/kvm.h
>> @@ -202,6 +202,7 @@ enum KVM_RISCV_SBI_EXT_ID {
>>     KVM_RISCV_SBI_EXT_DBCN,
>>     KVM_RISCV_SBI_EXT_STA,
>>     KVM_RISCV_SBI_EXT_SUSP,
>> +    KVM_RISCV_SBI_EXT_FWFT,
>>     KVM_RISCV_SBI_EXT_MAX,
>> };
>>
>> diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
>> index 4e0bba91d284..06e2d52a9b88 100644
>> --- a/arch/riscv/kvm/Makefile
>> +++ b/arch/riscv/kvm/Makefile
>> @@ -26,6 +26,7 @@ kvm-y += vcpu_onereg.o
>> kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o
>> kvm-y += vcpu_sbi.o
>> kvm-y += vcpu_sbi_base.o
>> +kvm-y += vcpu_sbi_fwft.o
>> kvm-y += vcpu_sbi_hsm.o
>> kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_sbi_pmu.o
>> kvm-y += vcpu_sbi_replace.o
>> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
>> index f81f06f82650..3b37deaed4e7 100644
>> --- a/arch/riscv/kvm/vcpu_sbi.c
>> +++ b/arch/riscv/kvm/vcpu_sbi.c
>> @@ -78,6 +78,10 @@ static const struct kvm_riscv_sbi_extension_entry
>> sbi_ext[] = {
>>         .ext_idx = KVM_RISCV_SBI_EXT_STA,
>>         .ext_ptr = &vcpu_sbi_ext_sta,
>>     },
>> +    {
>> +        .ext_idx = KVM_RISCV_SBI_EXT_FWFT,
>> +        .ext_ptr = &vcpu_sbi_ext_fwft,
>> +    },
>>     {
>>         .ext_idx = KVM_RISCV_SBI_EXT_EXPERIMENTAL,
>>         .ext_ptr = &vcpu_sbi_ext_experimental,
>> diff --git a/arch/riscv/kvm/vcpu_sbi_fwft.c b/arch/riscv/kvm/
>> vcpu_sbi_fwft.c
>> new file mode 100644
>> index 000000000000..fe608bf16558
>> --- /dev/null
>> +++ b/arch/riscv/kvm/vcpu_sbi_fwft.c
>> @@ -0,0 +1,187 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2025 Rivos Inc.
>> + *
>> + * Authors:
>> + *     Clément Léger <cleger@rivosinc.com>
>> + */
>> +
>> +#include <linux/errno.h>
>> +#include <linux/err.h>
>> +#include <linux/kvm_host.h>
>> +#include <asm/cpufeature.h>
>> +#include <asm/sbi.h>
>> +#include <asm/kvm_vcpu_sbi.h>
>> +#include <asm/kvm_vcpu_sbi_fwft.h>
>> +
>> +static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = {
>> +    SBI_FWFT_MISALIGNED_EXC_DELEG,
>> +    SBI_FWFT_LANDING_PAD,
>> +    SBI_FWFT_SHADOW_STACK,
>> +    SBI_FWFT_DOUBLE_TRAP,
>> +    SBI_FWFT_PTE_AD_HW_UPDATING,
>> +    SBI_FWFT_POINTER_MASKING_PMLEN,
>> +};
>> +
>> +static bool kvm_fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
>> +{
>> +    int i;
>> +
>> +    for (i = 0; i < ARRAY_SIZE(kvm_fwft_defined_features); i++) {
>> +        if (kvm_fwft_defined_features[i] == feature)
>> +            return true;
>> +    }
>> +
>> +    return false;
>> +}
>> +
>> +static const struct kvm_sbi_fwft_feature features[] = {
>> +};
>> +
>> +static struct kvm_sbi_fwft_config *
>> +kvm_sbi_fwft_get_config(struct kvm_vcpu *vcpu, enum
>> sbi_fwft_feature_t feature)
>> +{
>> +    int i = 0;
>> +    struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>> +
>> +    for (i = 0; i < ARRAY_SIZE(features); i++) {
>> +        if (fwft->configs[i].feature->id == feature)
>> +            return &fwft->configs[i];
>> +    }
>> +
>> +    return NULL;
>> +}
>> +
>> +static int kvm_fwft_get_feature(struct kvm_vcpu *vcpu, unsigned long
>> feature,
>> +                struct kvm_sbi_fwft_config **conf)
>> +{
>> +    struct kvm_sbi_fwft_config *tconf;
>> +
>> +    /* Feature are defined as 32 bits identifiers */
>> +    if (feature & ~(BIT_ULL(32) - 1))
>> +        return SBI_ERR_INVALID_PARAM;
>> +
>> +    tconf = kvm_sbi_fwft_get_config(vcpu, feature);
>> +    if (!tconf) {
>> +        if (kvm_fwft_is_defined_feature(feature))
>> +            return SBI_ERR_NOT_SUPPORTED;
>> +
>> +        return SBI_ERR_DENIED;
>> +    }
>> +
>> +    if (!tconf->supported)
>> +        return SBI_ERR_NOT_SUPPORTED;
>> +
>> +    *conf = tconf;
>> +
>> +    return SBI_SUCCESS;
>> +}
>> +
>> +static int kvm_sbi_fwft_set(struct kvm_vcpu *vcpu, unsigned long
>> feature,
>> +                unsigned long value, unsigned long flags)
>> +{
>> +    int ret;
>> +    struct kvm_sbi_fwft_config *conf;
>> +
>> +    ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>> +    if (ret)
>> +        return ret;
>> +
>> +    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_LOCKED;
>> +
>> +    conf->flags = flags;
>> +
>> +    return conf->feature->set(vcpu, conf, value);
>> +}
>> +
>> +static int kvm_sbi_fwft_get(struct kvm_vcpu *vcpu, unsigned long
>> feature,
>> +                unsigned long *value)
>> +{
>> +    int ret;
>> +    struct kvm_sbi_fwft_config *conf;
>> +
>> +    ret = kvm_fwft_get_feature(vcpu, feature, &conf);
>> +    if (ret)
>> +        return ret;
>> +
>> +    return conf->feature->get(vcpu, conf, value);
>> +}
>> +
>> +static int kvm_sbi_ext_fwft_handler(struct kvm_vcpu *vcpu, struct
>> kvm_run *run,
>> +                    struct kvm_vcpu_sbi_return *retdata)
>> +{
>> +    int ret = 0;
>> +    struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
>> +    unsigned long funcid = cp->a6;
>> +
>> +    switch (funcid) {
>> +    case SBI_EXT_FWFT_SET:
>> +        ret = kvm_sbi_fwft_set(vcpu, cp->a0, cp->a1, cp->a2);
>> +        break;
>> +    case SBI_EXT_FWFT_GET:
>> +        ret = kvm_sbi_fwft_get(vcpu, cp->a0, &retdata->out_val);
>> +        break;
>> +    default:
>> +        ret = SBI_ERR_NOT_SUPPORTED;
>> +        break;
>> +    }
>> +
>> +    retdata->err_val = ret;
>> +
>> +    return 0;
>> +}
>> +
>> +static int kvm_sbi_ext_fwft_init(struct kvm_vcpu *vcpu)
>> +{
>> +    struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>> +    const struct kvm_sbi_fwft_feature *feature;
>> +    struct kvm_sbi_fwft_config *conf;
>> +    int i;
>> +
>> +    fwft->configs = kcalloc(ARRAY_SIZE(features), sizeof(struct
>> kvm_sbi_fwft_config),
>> +                GFP_KERNEL);
>> +    if (!fwft->configs)
>> +        return -ENOMEM;
>> +
>> +    for (i = 0; i < ARRAY_SIZE(features); i++) {
>> +        feature = &features[i];
>> +        conf = &fwft->configs[i];
>> +        if (feature->supported)
>> +            conf->supported = feature->supported(vcpu);
>> +        else
>> +            conf->supported = true;
>> +
>> +        conf->feature = feature;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static void kvm_sbi_ext_fwft_deinit(struct kvm_vcpu *vcpu)
>> +{
>> +    struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>> +
>> +    kfree(fwft->configs);
>> +}
>> +
>> +static void kvm_sbi_ext_fwft_reset(struct kvm_vcpu *vcpu)
>> +{
>> +    int i = 0;
>> +    struct kvm_sbi_fwft *fwft = vcpu_to_fwft(vcpu);
>> +
>> +    for (i = 0; i < ARRAY_SIZE(features); i++)
>> +        fwft->configs[i].flags = 0;
>> +}
>> +
>> +const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_fwft = {
>> +    .extid_start = SBI_EXT_FWFT,
>> +    .extid_end = SBI_EXT_FWFT,
>> +    .handler = kvm_sbi_ext_fwft_handler,
>> +    .init = kvm_sbi_ext_fwft_init,
>> +    .deinit = kvm_sbi_ext_fwft_deinit,
>> +    .reset = kvm_sbi_ext_fwft_reset,
>> +};
>> -- 
>> 2.47.2
>>
>>