[PATCH] RISC-V KVM: Remove unnecessary HGATP csr_read

From: guoren@kernel.org
To: guoren@kernel.org
Cc: alex@ghiti.fr, anup@brainfault.org, aou@eecs.berkeley.edu,
	atish.patra@linux.dev, fangyu.yu@linux.alibaba.com,
	guoren@linux.alibaba.com, kvm-riscv@lists.infradead.org,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, palmer@dabbelt.com,
	paul.walmsley@sifive.com
Subject: [PATCH] RISC-V KVM: Remove unnecessary HGATP csr_read
Date: Tue, 19 Aug 2025 02:44:29 -0400	[thread overview]
Message-ID: <20250819064429.1947476-1-guoren@kernel.org> (raw)
In-Reply-To: <CAJF2gTQFWJzHhRoQ-oASO9nn1kC0dv+NuK-DD=JgfeHE90RWqw@mail.gmail.com>

From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>

The HGATP has been set to zero in gstage_mode_detect(), so there
is no need to save the old context. Unify the code convention
with gstage_mode_detect().

Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
---
This cleanup is based on yufang.yu's vmid fixup patch.
---
 arch/riscv/kvm/vmid.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/riscv/kvm/vmid.c b/arch/riscv/kvm/vmid.c
index 5f33625f4070..abb1c2bf2542 100644
--- a/arch/riscv/kvm/vmid.c
+++ b/arch/riscv/kvm/vmid.c
@@ -25,15 +25,12 @@ static DEFINE_SPINLOCK(vmid_lock);
 
 void __init kvm_riscv_gstage_vmid_detect(void)
 {
-	unsigned long old;
-
 	/* Figure-out number of VMID bits in HW */
-	old = csr_read(CSR_HGATP);
 	csr_write(CSR_HGATP, (kvm_riscv_gstage_mode << HGATP_MODE_SHIFT) | HGATP_VMID);
 	vmid_bits = csr_read(CSR_HGATP);
 	vmid_bits = (vmid_bits & HGATP_VMID) >> HGATP_VMID_SHIFT;
 	vmid_bits = fls_long(vmid_bits);
-	csr_write(CSR_HGATP, old);
+	csr_write(CSR_HGATP, 0);
 
 	/* We polluted local TLB so flush all guest TLB */
 	kvm_riscv_local_hfence_gvma_all();
-- 
2.40.1


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