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[86.49.253.11]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4806ce4c3c6sm150902865e9.10.2026.01.29.12.25.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Jan 2026 12:25:10 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Date: Thu, 29 Jan 2026 20:25:08 +0000 Message-Id: From: =?utf-8?q?Radim_Kr=C4=8Dm=C3=A1=C5=99?= Subject: [SUGGESTION] KVM: RISC-V: detect gstage mode hierarchy Cc: , , , , , , , , , , , , , , , To: References: <20260125150450.27068-1-fangyu.yu@linux.alibaba.com> <20260125150450.27068-2-fangyu.yu@linux.alibaba.com> In-Reply-To: X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTI5MDE0NyBTYWx0ZWRfX+lp5jhC2WQJ+ 6CkVas6yCIoKE70vUPcixxXFkvSYiVo8zkGeKGpMcmQa/OZTbesojX54JQItT/dX1RWOifx9i/o BPioYQ9UHtY9CXr6Vkm+ltNQBZA6/uFcgcA860eVbjIh8S1sTVnz3JP7eQq8YB71F8PMTos0v8s T+Vfw3dL+JQGlgsdV1xfuzzZLE0SSYCLm1J5LnGteLc3l3IvmLDJ5wM1qUTLlrtvG/QAvPI5djj FIBEm/HJTFE8V8t4EJOo2CnV5xJLHfn0vOFku2XwMxt2nVOPcZilV3ESGuUYrmz3vf5h8INCvPR rABpte9Xi1IB7C/s+vQY+bDT/SWkgwcYbNgCeHMlNe7cg5YW3+xJNu5o3/989xG0c8csg2tQshP YDQAmrkHZ7KpiSRt2zbrtJZxQhaova+el8VPZI63nHl6ypbSAx2/fz/TdWE1l3XSPRKPDy0aEKl 8mMIzn4A44JIjaNZY0A== X-Authority-Analysis: v=2.4 cv=U/6fzOru c=1 sm=1 tr=0 ts=697bc227 cx=c_pps a=hnmNkyzTK/kJ09Xio7VxxA==:117 a=HFCiZzTCIv7qJCpyeE1rag==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=M51BFTxLslgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=EUspDBNiAAAA:8 a=B30jFbksMaAZlFPmlSQA:9 a=QEXdDO2ut3YA:10 a=PEH46H7Ffwr30OY-TuGO:22 X-Proofpoint-ORIG-GUID: ypNKwQa4Zo1evqOWS4yz8QWxCBanoynL X-Proofpoint-GUID: ypNKwQa4Zo1evqOWS4yz8QWxCBanoynL X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-01-29_03,2026-01-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 impostorscore=0 bulkscore=0 spamscore=0 clxscore=1015 adultscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2601290147 Content-Type: text/plain; charset="utf-8" 2026-01-29T15:27:35+00:00, Radim Kr=C4=8Dm=C3=A1=C5=99 : > (I'll reply with a patch later.) Something like this would avoid a bit of technical debt. The solution could be even more generic by returning a bitmap of supported modes, but that would be larger refactoring... Feel free to use it in the series, but beware: only compile-tested. It's late and hope it at least boots. :) Thanks. ---8<--- RISC-V ISA does not require a hierarchy of standard hgatp mode (i.e. 57x4 does not depend on 48x4 onr 39x4), yet future patches want to assume that the hierarchy exists, for simplicity. Only accept a hgatp mode if all narrower modes are supported as well. All sensible RISC-V implementations should have the hierarchy, since it's very cheap to add the narrower modes. Signed-off-by: Radim Kr=C4=8Dm=C3=A1=C5=99 --- The hunk that removes the default values at the beginning of gstage.c should have been a separate patch, sorry. --- arch/riscv/include/asm/kvm_gstage.h | 2 +- arch/riscv/kvm/gstage.c | 66 ++++++++++++----------------- arch/riscv/kvm/main.c | 6 ++- 3 files changed, 32 insertions(+), 42 deletions(-) diff --git a/arch/riscv/include/asm/kvm_gstage.h b/arch/riscv/include/asm/k= vm_gstage.h index 595e2183173e..18db474ce583 100644 --- a/arch/riscv/include/asm/kvm_gstage.h +++ b/arch/riscv/include/asm/kvm_gstage.h @@ -67,6 +67,6 @@ void kvm_riscv_gstage_unmap_range(struct kvm_gstage *gsta= ge, =20 void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa= _t end); =20 -void kvm_riscv_gstage_mode_detect(void); +unsigned long kvm_riscv_gstage_mode_detect(void); =20 #endif diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c index b67d60d722c2..678b304553bc 100644 --- a/arch/riscv/kvm/gstage.c +++ b/arch/riscv/kvm/gstage.c @@ -11,13 +11,8 @@ #include #include =20 -#ifdef CONFIG_64BIT -unsigned long kvm_riscv_gstage_mode __ro_after_init =3D HGATP_MODE_SV39X4; -unsigned long kvm_riscv_gstage_pgd_levels __ro_after_init =3D 3; -#else -unsigned long kvm_riscv_gstage_mode __ro_after_init =3D HGATP_MODE_SV32X4; -unsigned long kvm_riscv_gstage_pgd_levels __ro_after_init =3D 2; -#endif +unsigned long kvm_riscv_gstage_mode __ro_after_init; +unsigned long kvm_riscv_gstage_pgd_levels __ro_after_init; =20 #define gstage_pte_leaf(__ptep) \ (pte_val(*(__ptep)) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC)) @@ -313,47 +308,38 @@ void kvm_riscv_gstage_wp_range(struct kvm_gstage *gst= age, gpa_t start, gpa_t end } } =20 -void __init kvm_riscv_gstage_mode_detect(void) +static inline unsigned long __init __kvm_riscv_gstage_mode_detect(void) { #ifdef CONFIG_64BIT - /* Try Sv57x4 G-stage mode */ - csr_write(CSR_HGATP, HGATP_MODE_SV57X4 << HGATP_MODE_SHIFT); - if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) =3D=3D HGATP_MODE_SV57X4) { - kvm_riscv_gstage_mode =3D HGATP_MODE_SV57X4; - kvm_riscv_gstage_pgd_levels =3D 5; - goto done; - } - - /* Try Sv48x4 G-stage mode */ - csr_write(CSR_HGATP, HGATP_MODE_SV48X4 << HGATP_MODE_SHIFT); - if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) =3D=3D HGATP_MODE_SV48X4) { - kvm_riscv_gstage_mode =3D HGATP_MODE_SV48X4; - kvm_riscv_gstage_pgd_levels =3D 4; - goto done; - } - - /* Try Sv39x4 G-stage mode */ csr_write(CSR_HGATP, HGATP_MODE_SV39X4 << HGATP_MODE_SHIFT); - if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) =3D=3D HGATP_MODE_SV39X4) { - kvm_riscv_gstage_mode =3D HGATP_MODE_SV39X4; - kvm_riscv_gstage_pgd_levels =3D 3; - goto done; - } + if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) !=3D HGATP_MODE_SV39X4) + return HGATP_MODE_OFF; + + csr_write(CSR_HGATP, HGATP_MODE_SV48X4 << HGATP_MODE_SHIFT); + if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) !=3D HGATP_MODE_SV48X4) + return HGATP_MODE_SV39X4; + + csr_write(CSR_HGATP, HGATP_MODE_SV57X4 << HGATP_MODE_SHIFT); + if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) !=3D HGATP_MODE_SV57X4) + return HGATP_MODE_SV48X4; + + return HGATP_MODE_SV57X4; #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) =3D=3D HGATP_MODE_SV32X4) { - kvm_riscv_gstage_mode =3D HGATP_MODE_SV32X4; - kvm_riscv_gstage_pgd_levels =3D 2; - goto done; - } + if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) !=3D HGATP_MODE_SV32X4) + return HGATP_MODE_OFF; + + return HGATP_MODE_SV32X4; #endif +} =20 - /* KVM depends on !HGATP_MODE_OFF */ - kvm_riscv_gstage_mode =3D HGATP_MODE_OFF; - kvm_riscv_gstage_pgd_levels =3D 0; +/* We could probably omit the HGATP write and fence. */ +unsigned long __init kvm_riscv_gstage_mode_detect(void) +{ + unsigned long gstage_mode =3D __kvm_riscv_gstage_mode_detect(); =20 -done: csr_write(CSR_HGATP, 0); kvm_riscv_local_hfence_gvma_all(); + + return gstage_mode; } diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c index 45536af521f0..58fd6ae8e04a 100644 --- a/arch/riscv/kvm/main.c +++ b/arch/riscv/kvm/main.c @@ -104,19 +104,23 @@ static int __init riscv_kvm_init(void) if (rc && rc !=3D -ENODEV) return rc; =20 - kvm_riscv_gstage_mode_detect(); + kvm_riscv_gstage_mode =3D kvm_riscv_gstage_mode_detect(); switch (kvm_riscv_gstage_mode) { case HGATP_MODE_SV32X4: str =3D "Sv32x4"; + kvm_riscv_gstage_pgd_levels =3D 2; break; case HGATP_MODE_SV39X4: str =3D "Sv39x4"; + kvm_riscv_gstage_pgd_levels =3D 3; break; case HGATP_MODE_SV48X4: str =3D "Sv48x4"; + kvm_riscv_gstage_pgd_levels =3D 4; break; case HGATP_MODE_SV57X4: str =3D "Sv57x4"; + kvm_riscv_gstage_pgd_levels =3D 5; break; default: kvm_riscv_nacl_exit(); --=20 2.51.0