linux-kernel - [PATCH V4 RESEND 1/3] RISC-V: KVM: Write hgatp register with valid mode bits

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Message-Id: <20250821142542.2472079-2-guoren@kernel.org>
Date: Thu, 21 Aug 2025 10:25:40 -0400
From: guoren@...nel.org
To: guoren@...nel.org,
	troy.mitchell@...ux.dev
Cc: alex@...ti.fr,
	anup@...infault.org,
	aou@...s.berkeley.edu,
	atish.patra@...ux.dev,
	fangyu.yu@...ux.alibaba.com,
	guoren@...ux.alibaba.com,
	kvm-riscv@...ts.infradead.org,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	palmer@...belt.com,
	paul.walmsley@...ive.com,
	Nutty Liu <nutty.liu@...mail.com>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: [PATCH V4 RESEND 1/3] RISC-V: KVM: Write hgatp register with valid mode bits

From: Fangyu Yu <fangyu.yu@...ux.alibaba.com>

According to the RISC-V Privileged Architecture Spec, when MODE=Bare
is selected,software must write zero to the remaining fields of hgatp.

We have detected the valid mode supported by the HW before, So using a
valid mode to detect how many vmid bits are supported.

Fixes: fd7bb4a251df ("RISC-V: KVM: Implement VMID allocator")
Reviewed-by: Nutty Liu <nutty.liu@...mail.com>
Reviewed-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Reviewed-by: Guo Ren (Alibaba DAMO Academy) <guoren@...nel.org>
Signed-off-by: Fangyu Yu <fangyu.yu@...ux.alibaba.com>
Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@...nel.org>
---
 arch/riscv/kvm/vmid.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kvm/vmid.c b/arch/riscv/kvm/vmid.c
index 3b426c800480..5f33625f4070 100644
--- a/arch/riscv/kvm/vmid.c
+++ b/arch/riscv/kvm/vmid.c
@@ -14,6 +14,7 @@
 #include <linux/smp.h>
 #include <linux/kvm_host.h>
 #include <asm/csr.h>
+#include <asm/kvm_mmu.h>
 #include <asm/kvm_tlb.h>
 #include <asm/kvm_vmid.h>
 
@@ -28,7 +29,7 @@ void __init kvm_riscv_gstage_vmid_detect(void)
 
 	/* Figure-out number of VMID bits in HW */
 	old = csr_read(CSR_HGATP);
-	csr_write(CSR_HGATP, old | HGATP_VMID);
+	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);
-- 
2.40.1