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RISC-V: KVM: Write hgatp register with valid mode bits

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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: fd7bb4a251 ("RISC-V: KVM: Implement VMID allocator")
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Reviewed-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
Link: https://lore.kernel.org/r/20250821142542.2472079-2-guoren@kernel.org
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Fangyu Yu 2025-08-21 10:25:40 -04:00 committed by Anup Patel
parent dbe3d1d160
commit 2b351e3d04
1 changed files with 2 additions and 1 deletions
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3
arch/riscv/kvm/vmid.c
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@ -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);