linux-kernel - [PATCH 1/5] RISC-V: KVM: Forward SEED CSR access to user space

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Date: Wed, 14 Feb 2024 18:07:53 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Paolo Bonzini <pbonzini@...hat.com>,
	Atish Patra <atishp@...shpatra.org>,
	Shuah Khan <shuah@...nel.org>
Cc: Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Anup Patel <anup@...infault.org>,
	kvm@...r.kernel.org,
	kvm-riscv@...ts.infradead.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Anup Patel <apatel@...tanamicro.com>
Subject: [PATCH 1/5] RISC-V: KVM: Forward SEED CSR access to user space

The SEED CSR access from VS/VU mode (guest) will always trap to
HS-mode (KVM) when Zkr extension is available to the Guest/VM.

We must forward this CSR access to KVM user space so that it
can be emulated based on the method chosen by VMM.

Fixes: f370b4e668f0 ("RISC-V: KVM: Allow scalar crypto extensions for Guest/VM")
Signed-off-by: Anup Patel <apatel@...tanamicro.com>
---
 arch/riscv/kvm/vcpu_insn.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
index 7a6abed41bc1..ee7215f4071f 100644
--- a/arch/riscv/kvm/vcpu_insn.c
+++ b/arch/riscv/kvm/vcpu_insn.c
@@ -7,6 +7,8 @@
 #include <linux/bitops.h>
 #include <linux/kvm_host.h>
 
+#include <asm/cpufeature.h>
+
 #define INSN_OPCODE_MASK	0x007c
 #define INSN_OPCODE_SHIFT	2
 #define INSN_OPCODE_SYSTEM	28
@@ -213,9 +215,20 @@ struct csr_func {
 		    unsigned long wr_mask);
 };
 
+static int seed_csr_rmw(struct kvm_vcpu *vcpu, unsigned int csr_num,
+			unsigned long *val, unsigned long new_val,
+			unsigned long wr_mask)
+{
+	if (!riscv_isa_extension_available(vcpu->arch.isa, ZKR))
+		return KVM_INSN_ILLEGAL_TRAP;
+
+	return KVM_INSN_EXIT_TO_USER_SPACE;
+}
+
 static const struct csr_func csr_funcs[] = {
 	KVM_RISCV_VCPU_AIA_CSR_FUNCS
 	KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS
+	{ .base = CSR_SEED, .count = 1, .func = seed_csr_rmw },
 };
 
 /**
-- 
2.34.1