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Message-ID: <aKSJtqea0x0r44Tq@troy-wujie14pro-arch>
Date: Tue, 19 Aug 2025 22:27:02 +0800
From: Troy Mitchell <troy.mitchell@...ux.dev>
To: guoren@...nel.org, paul.walmsley@...ive.com, anup@...infault.org,
atish.patra@...ux.dev, fangyu.yu@...ux.alibaba.com
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
Troy Mitchell <troy.mitchell@...ux.dev>
Subject: Re: [PATCH] RISC-V: KVM: Prevent HGATP_MODE_BARE passed
On Mon, Aug 18, 2025 at 08:46:43PM -0400, guoren@...nel.org wrote:
> From: "Guo Ren (Alibaba DAMO Academy)" <guoren@...nel.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@...nel.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@...ux.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@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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