RISC-V: KVM: Prevent HGATP_MODE_BARE passed

Current kvm_riscv_gstage_mode_detect() assumes H-extension must
have HGATP_MODE_SV39X4/SV32X4 at least, but the spec allows
H-extension with HGATP_MODE_BARE alone. The KVM depends on
!HGATP_MODE_BARE at least, so enhance the gstage-mode-detect
to block HGATP_MODE_BARE.

Move gstage-mode-check closer to gstage-mode-detect to prevent
unnecessary init.

Reviewed-by: Troy Mitchell <troy.mitchell@linux.dev>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
Reviewed-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250821142542.2472079-4-guoren@kernel.org
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index 24c270d6d0e27457a8b228593a120e506758b09a..b67d60d722c2fb30465073a1863b2cdccb8cc510 100644 (file)
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -321,7 +321,7 @@ void __init kvm_riscv_gstage_mode_detect(void)
        if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == HGATP_MODE_SV57X4) {
                kvm_riscv_gstage_mode = HGATP_MODE_SV57X4;
                kvm_riscv_gstage_pgd_levels = 5;
-               goto skip_sv48x4_test;
+               goto done;
        }
 
        /* Try Sv48x4 G-stage mode */
@@ -329,10 +329,31 @@ void __init kvm_riscv_gstage_mode_detect(void)
        if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == HGATP_MODE_SV48X4) {
                kvm_riscv_gstage_mode = HGATP_MODE_SV48X4;
                kvm_riscv_gstage_pgd_levels = 4;
+               goto done;
        }
-skip_sv48x4_test:
 
+       /* Try Sv39x4 G-stage mode */
+       csr_write(CSR_HGATP, HGATP_MODE_SV39X4 << HGATP_MODE_SHIFT);
+       if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == HGATP_MODE_SV39X4) {
+               kvm_riscv_gstage_mode = HGATP_MODE_SV39X4;
+               kvm_riscv_gstage_pgd_levels = 3;
+               goto done;
+       }
+#else /* CONFIG_32BIT */
+       /* Try Sv32x4 G-stage mode */
+       csr_write(CSR_HGATP, HGATP_MODE_SV32X4 << HGATP_MODE_SHIFT);
+       if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == HGATP_MODE_SV32X4) {
+               kvm_riscv_gstage_mode = HGATP_MODE_SV32X4;
+               kvm_riscv_gstage_pgd_levels = 2;
+               goto done;
+       }
+#endif
+
+       /* KVM depends on !HGATP_MODE_OFF */
+       kvm_riscv_gstage_mode = HGATP_MODE_OFF;
+       kvm_riscv_gstage_pgd_levels = 0;
+
+done:
        csr_write(CSR_HGATP, 0);
        kvm_riscv_local_hfence_gvma_all();
-#endif
 }

diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index 67c876de74efb1d03f7b4d87cef6febec506b34d..77dc1655b442380a9c31daf70dce622df32e9f0d 100644 (file)
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -93,6 +93,23 @@ static int __init riscv_kvm_init(void)
                return rc;
 
        kvm_riscv_gstage_mode_detect();
+       switch (kvm_riscv_gstage_mode) {
+       case HGATP_MODE_SV32X4:
+               str = "Sv32x4";
+               break;
+       case HGATP_MODE_SV39X4:
+               str = "Sv39x4";
+               break;
+       case HGATP_MODE_SV48X4:
+               str = "Sv48x4";
+               break;
+       case HGATP_MODE_SV57X4:
+               str = "Sv57x4";
+               break;
+       default:
+               kvm_riscv_nacl_exit();
+               return -ENODEV;
+       }
 
        kvm_riscv_gstage_vmid_detect();
 
@@ -135,22 +152,6 @@ static int __init riscv_kvm_init(void)
                         (rc) ? slist : "no features");
        }
 
-       switch (kvm_riscv_gstage_mode) {
-       case HGATP_MODE_SV32X4:
-               str = "Sv32x4";
-               break;
-       case HGATP_MODE_SV39X4:
-               str = "Sv39x4";
-               break;
-       case HGATP_MODE_SV48X4:
-               str = "Sv48x4";
-               break;
-       case HGATP_MODE_SV57X4:
-               str = "Sv57x4";
-               break;
-       default:
-               return -ENODEV;
-       }
        kvm_info("using %s G-stage page table format\n", str);
 
        kvm_info("VMID %ld bits available\n", kvm_riscv_gstage_vmid_bits());