RISC-V: KVM: Prevent HGATP_MODE_BARE passed

[PATCH] RISC-V: KVM: Prevent HGATP_MODE_BARE passed

Posted by guoren@kernel.org 1 month, 2 weeks ago

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

urrent 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.

Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
---
 arch/riscv/kvm/gstage.c | 27 ++++++++++++++++++++++++---
 arch/riscv/kvm/main.c   | 35 +++++++++++++++++------------------
 2 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index 24c270d6d0e2..b67d60d722c2 100644
--- 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 67c876de74ef..8ee7aaa74ddc 100644
--- 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:
+		return -ENODEV;
+	}
+	kvm_info("using %s G-stage page table format\n", str);
 
 	kvm_riscv_gstage_vmid_detect();
 
@@ -135,24 +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());
 
 	if (kvm_riscv_aia_available())
-- 
2.40.1

Re: [PATCH] RISC-V: KVM: Prevent HGATP_MODE_BARE passed

Posted by Troy Mitchell 1 month, 2 weeks ago

On Mon, Aug 18, 2025 at 08:46:43PM -0400, guoren@kernel.org wrote:
> From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>
> 
> urrent 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.
> 
> Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
> ---
>  arch/riscv/kvm/gstage.c | 27 ++++++++++++++++++++++++---
>  arch/riscv/kvm/main.c   | 35 +++++++++++++++++------------------
>  2 files changed, 41 insertions(+), 21 deletions(-)
Reviewed-by: Troy Mitchell <troy.mitchell@linux.dev>

> 
> diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
> index 24c270d6d0e2..b67d60d722c2 100644
> --- 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 67c876de74ef..8ee7aaa74ddc 100644
> --- 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:
> +		return -ENODEV;
> +	}
> +	kvm_info("using %s G-stage page table format\n", str);
>  
>  	kvm_riscv_gstage_vmid_detect();
>  
> @@ -135,24 +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());
>  
>  	if (kvm_riscv_aia_available())
> -- 
> 2.40.1
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH] RISC-V: KVM: Prevent HGATP_MODE_BARE passed

Posted by fangyu.yu@linux.alibaba.com 1 month, 2 weeks ago

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

This patch helps to detect hardware function missing in advance,
prevent software from entering incorrect logic.

Reviewed-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>

>Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
>---
> arch/riscv/kvm/gstage.c | 27 ++++++++++++++++++++++++---
> arch/riscv/kvm/main.c   | 35 +++++++++++++++++------------------
> 2 files changed, 41 insertions(+), 21 deletions(-)
>
>diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
>index 24c270d6d0e2..b67d60d722c2 100644
>--- 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 67c876de74ef..8ee7aaa74ddc 100644
>--- 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:
>+		return -ENODEV;
>+	}
>+	kvm_info("using %s G-stage page table format\n", str);
>
> 	kvm_riscv_gstage_vmid_detect();
>
>@@ -135,24 +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());
>
> 	if (kvm_riscv_aia_available())
>--
>2.40.1