[PATCH v6 0/4] Support runtime configuration for per-VM's HGATP mode

[PATCH v6 0/4] Support runtime configuration for per-VM's HGATP mode

[fangyu.yu]

From: Fangyu Yu <fangyu.yu@linux.alibaba.com>

Currently, RISC-V KVM hardcodes the G-stage page table format (HGATP mode)
to the maximum mode detected at boot time (e.g., SV57x4 if supported). but
often such a wide GPA is unnecessary, just as a host sometimes doesn't need
sv57.

This patch introduces per-VM configurability of the G-stage mode via a new
KVM capability: KVM_CAP_RISCV_SET_HGATP_MODE. User-space can now explicitly
request a specific HGATP mode (SV39x4, SV48x4, SV57x4 or SV32x4) during
VM creation.

---
Changes in v6 (Anup's suggestions):
    - Reworked kvm_riscv_gstage_gpa_bits() and kvm_riscv_gstage_gpa_size() to
      take "unsigned long pgd_levels" instead of "struct kvm_arch *".
    - Moved kvm_riscv_gstage_mode() helper from kvm_host.h to kvm_gstage.h.
    - Renamed kvm->arch.kvm_riscv_gstage_pgd_levels to kvm->arch.pgd_levels.
    - Added pgd_levels to struct kvm_gstage to avoid repeated
      gstage->kvm->arch pointer chasing.
    - Link to v5:
      https://lore.kernel.org/linux-riscv/20260204134507.33912-1-fangyu.yu@linux.alibaba.com/
---
Changes in v5:
    - Use architectural HGATP.MODE encodings as the bit index for the supported-mode
      bitmap and for the VM-mode selection UAPI; no new UAPI mode/bit defines are
      introduced(per Radim).
    - Allow KVM_CAP_RISCV_SET_HGATP_MODE on RV32 as well(per Drew).
    - Link to v4:
      https://lore.kernel.org/linux-riscv/20260202140716.34323-1-fangyu.yu@linux.alibaba.com/
---
Changes in v4:
    - Extend kvm_riscv_gstage_mode_detect() to probe all HGATP.MODE values
      supported by the host and record them in a bitmask.
    - Treat unexpected pgd_levels in kvm_riscv_gstage_mode() as an internal error
      (e.g. WARN_ON_ONCE())(per Radim).
    - Move kvm_riscv_gstage_gpa_bits() and kvm_riscv_gstage_gpa_size() to header
      as static inline helpers(per Radim).
    - Drop gstage_mode_user_initialized and Remove the kvm_debug() message from
      KVM_CAP_RISCV_SET_HGATP_MODE(per Radim).
    - Link to v3:
      https://lore.kernel.org/linux-riscv/20260125150450.27068-1-fangyu.yu@linux.alibaba.com/
---
Changes in v3:
    - Reworked the patch formatting (per Drew).
    - Dropped kvm->arch.kvm_riscv_gstage_mode and derive HGATP.MODE from
      kvm_riscv_gstage_pgd_levels via a helper, avoiding redundant per-VM state(per Drew).
    - Removed kvm_riscv_gstage_max_mode and keep only kvm_riscv_gstage_max_pgd_levels
      for host capability detection(per Drew).
    - Other initialization and return value issues(per Drew).
    - Enforce that KVM_CAP_RISCV_SET_HGATP_MODE can only be enabled before any vCPUs
      are created by rejecting the ioctl once kvm->created_vcpus is non-zero(per Radim).
    - Add a memslot safety check and reject the capability unless
      kvm_are_all_memslots_empty(kvm) is true, ensuring the G-stage format is not
      changed after any memslots have been installed(per Radim).
    - Link to v2:
      https://lore.kernel.org/linux-riscv/20260105143232.76715-1-fangyu.yu@linux.alibaba.com/

Fangyu Yu (4):
  RISC-V: KVM: Support runtime configuration for per-VM's HGATP mode
  RISC-V: KVM: Cache gstage pgd_levels in struct kvm_gstage
  RISC-V: KVM: Detect and expose supported HGATP G-stage modes
  RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE

 Documentation/virt/kvm/api.rst      |  27 ++++++++
 arch/riscv/include/asm/kvm_gstage.h |  58 ++++++++++++++--
 arch/riscv/include/asm/kvm_host.h   |   1 +
 arch/riscv/kvm/gstage.c             | 102 ++++++++++++++--------------
 arch/riscv/kvm/main.c               |  12 ++--
 arch/riscv/kvm/mmu.c                |  70 ++++++-------------
 arch/riscv/kvm/vm.c                 |  20 +++++-
 arch/riscv/kvm/vmid.c               |   3 +-
 include/uapi/linux/kvm.h            |   1 +
 9 files changed, 178 insertions(+), 116 deletions(-)

-- 
2.50.1

[PATCH v6 1/4] RISC-V: KVM: Support runtime configuration for per-VM's HGATP mode

[fangyu.yu]

From: Fangyu Yu <fangyu.yu@linux.alibaba.com>

Introduces one per-VM architecture-specific fields to support runtime
configuration of the G-stage page table format:

- kvm->arch.pgd_levels: the corresponding number of page table levels
  for the selected mode.

These fields replace the previous global variables
kvm_riscv_gstage_mode and kvm_riscv_gstage_pgd_levels, enabling different
virtual machines to independently select their G-stage page table format
instead of being forced to share the maximum mode detected by the kernel
at boot time.

Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
---
 arch/riscv/include/asm/kvm_gstage.h | 37 ++++++++++++----
 arch/riscv/include/asm/kvm_host.h   |  1 +
 arch/riscv/kvm/gstage.c             | 65 ++++++++++++++---------------
 arch/riscv/kvm/main.c               | 12 +++---
 arch/riscv/kvm/mmu.c                | 20 +++++----
 arch/riscv/kvm/vm.c                 |  2 +-
 arch/riscv/kvm/vmid.c               |  3 +-
 7 files changed, 83 insertions(+), 57 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_gstage.h b/arch/riscv/include/asm/kvm_gstage.h
index 595e2183173e..5aa58d1f692a 100644
--- a/arch/riscv/include/asm/kvm_gstage.h
+++ b/arch/riscv/include/asm/kvm_gstage.h
@@ -29,16 +29,22 @@ struct kvm_gstage_mapping {
 #define kvm_riscv_gstage_index_bits	10
 #endif
 
-extern unsigned long kvm_riscv_gstage_mode;
-extern unsigned long kvm_riscv_gstage_pgd_levels;
+extern unsigned long kvm_riscv_gstage_max_pgd_levels;
 
 #define kvm_riscv_gstage_pgd_xbits	2
 #define kvm_riscv_gstage_pgd_size	(1UL << (HGATP_PAGE_SHIFT + kvm_riscv_gstage_pgd_xbits))
-#define kvm_riscv_gstage_gpa_bits	(HGATP_PAGE_SHIFT + \
-					 (kvm_riscv_gstage_pgd_levels * \
-					  kvm_riscv_gstage_index_bits) + \
-					 kvm_riscv_gstage_pgd_xbits)
-#define kvm_riscv_gstage_gpa_size	((gpa_t)(1ULL << kvm_riscv_gstage_gpa_bits))
+
+static inline unsigned long kvm_riscv_gstage_gpa_bits(unsigned long pgd_levels)
+{
+	return (HGATP_PAGE_SHIFT +
+		pgd_levels * kvm_riscv_gstage_index_bits +
+		kvm_riscv_gstage_pgd_xbits);
+}
+
+static inline gpa_t kvm_riscv_gstage_gpa_size(unsigned long pgd_levels)
+{
+	return BIT_ULL(kvm_riscv_gstage_gpa_bits(pgd_levels));
+}
 
 bool kvm_riscv_gstage_get_leaf(struct kvm_gstage *gstage, gpa_t addr,
 			       pte_t **ptepp, u32 *ptep_level);
@@ -69,4 +75,21 @@ void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
 
 void kvm_riscv_gstage_mode_detect(void);
 
+static inline unsigned long kvm_riscv_gstage_mode(unsigned long pgd_levels)
+{
+	switch (pgd_levels) {
+	case 2:
+		return HGATP_MODE_SV32X4;
+	case 3:
+		return HGATP_MODE_SV39X4;
+	case 4:
+		return HGATP_MODE_SV48X4;
+	case 5:
+		return HGATP_MODE_SV57X4;
+	default:
+		WARN_ON_ONCE(1);
+		return HGATP_MODE_OFF;
+	}
+}
+
 #endif
diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 24585304c02b..478f699e9dec 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -94,6 +94,7 @@ struct kvm_arch {
 	/* G-stage page table */
 	pgd_t *pgd;
 	phys_addr_t pgd_phys;
+	unsigned long pgd_levels;
 
 	/* Guest Timer */
 	struct kvm_guest_timer timer;
diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index b67d60d722c2..4beb9322fe76 100644
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -12,22 +12,21 @@
 #include <asm/kvm_gstage.h>
 
 #ifdef CONFIG_64BIT
-unsigned long kvm_riscv_gstage_mode __ro_after_init = HGATP_MODE_SV39X4;
-unsigned long kvm_riscv_gstage_pgd_levels __ro_after_init = 3;
+unsigned long kvm_riscv_gstage_max_pgd_levels __ro_after_init = 3;
 #else
-unsigned long kvm_riscv_gstage_mode __ro_after_init = HGATP_MODE_SV32X4;
-unsigned long kvm_riscv_gstage_pgd_levels __ro_after_init = 2;
+unsigned long kvm_riscv_gstage_max_pgd_levels __ro_after_init = 2;
 #endif
 
 #define gstage_pte_leaf(__ptep)	\
 	(pte_val(*(__ptep)) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC))
 
-static inline unsigned long gstage_pte_index(gpa_t addr, u32 level)
+static inline unsigned long gstage_pte_index(struct kvm_gstage *gstage,
+					     gpa_t addr, u32 level)
 {
 	unsigned long mask;
 	unsigned long shift = HGATP_PAGE_SHIFT + (kvm_riscv_gstage_index_bits * level);
 
-	if (level == (kvm_riscv_gstage_pgd_levels - 1))
+	if (level == gstage->kvm->arch.pgd_levels - 1)
 		mask = (PTRS_PER_PTE * (1UL << kvm_riscv_gstage_pgd_xbits)) - 1;
 	else
 		mask = PTRS_PER_PTE - 1;
@@ -40,12 +39,13 @@ static inline unsigned long gstage_pte_page_vaddr(pte_t pte)
 	return (unsigned long)pfn_to_virt(__page_val_to_pfn(pte_val(pte)));
 }
 
-static int gstage_page_size_to_level(unsigned long page_size, u32 *out_level)
+static int gstage_page_size_to_level(struct kvm_gstage *gstage, unsigned long page_size,
+				     u32 *out_level)
 {
 	u32 i;
 	unsigned long psz = 1UL << 12;
 
-	for (i = 0; i < kvm_riscv_gstage_pgd_levels; i++) {
+	for (i = 0; i < gstage->kvm->arch.pgd_levels; i++) {
 		if (page_size == (psz << (i * kvm_riscv_gstage_index_bits))) {
 			*out_level = i;
 			return 0;
@@ -55,21 +55,23 @@ static int gstage_page_size_to_level(unsigned long page_size, u32 *out_level)
 	return -EINVAL;
 }
 
-static int gstage_level_to_page_order(u32 level, unsigned long *out_pgorder)
+static int gstage_level_to_page_order(struct kvm_gstage *gstage, u32 level,
+				      unsigned long *out_pgorder)
 {
-	if (kvm_riscv_gstage_pgd_levels < level)
+	if (gstage->kvm->arch.pgd_levels < level)
 		return -EINVAL;
 
 	*out_pgorder = 12 + (level * kvm_riscv_gstage_index_bits);
 	return 0;
 }
 
-static int gstage_level_to_page_size(u32 level, unsigned long *out_pgsize)
+static int gstage_level_to_page_size(struct kvm_gstage *gstage, u32 level,
+				     unsigned long *out_pgsize)
 {
 	int rc;
 	unsigned long page_order = PAGE_SHIFT;
 
-	rc = gstage_level_to_page_order(level, &page_order);
+	rc = gstage_level_to_page_order(gstage, level, &page_order);
 	if (rc)
 		return rc;
 
@@ -81,11 +83,11 @@ bool kvm_riscv_gstage_get_leaf(struct kvm_gstage *gstage, gpa_t addr,
 			       pte_t **ptepp, u32 *ptep_level)
 {
 	pte_t *ptep;
-	u32 current_level = kvm_riscv_gstage_pgd_levels - 1;
+	u32 current_level = gstage->kvm->arch.pgd_levels - 1;
 
 	*ptep_level = current_level;
 	ptep = (pte_t *)gstage->pgd;
-	ptep = &ptep[gstage_pte_index(addr, current_level)];
+	ptep = &ptep[gstage_pte_index(gstage, addr, current_level)];
 	while (ptep && pte_val(ptep_get(ptep))) {
 		if (gstage_pte_leaf(ptep)) {
 			*ptep_level = current_level;
@@ -97,7 +99,7 @@ bool kvm_riscv_gstage_get_leaf(struct kvm_gstage *gstage, gpa_t addr,
 			current_level--;
 			*ptep_level = current_level;
 			ptep = (pte_t *)gstage_pte_page_vaddr(ptep_get(ptep));
-			ptep = &ptep[gstage_pte_index(addr, current_level)];
+			ptep = &ptep[gstage_pte_index(gstage, addr, current_level)];
 		} else {
 			ptep = NULL;
 		}
@@ -110,7 +112,7 @@ static void gstage_tlb_flush(struct kvm_gstage *gstage, u32 level, gpa_t addr)
 {
 	unsigned long order = PAGE_SHIFT;
 
-	if (gstage_level_to_page_order(level, &order))
+	if (gstage_level_to_page_order(gstage, level, &order))
 		return;
 	addr &= ~(BIT(order) - 1);
 
@@ -125,9 +127,9 @@ int kvm_riscv_gstage_set_pte(struct kvm_gstage *gstage,
 			     struct kvm_mmu_memory_cache *pcache,
 			     const struct kvm_gstage_mapping *map)
 {
-	u32 current_level = kvm_riscv_gstage_pgd_levels - 1;
+	u32 current_level = gstage->kvm->arch.pgd_levels - 1;
 	pte_t *next_ptep = (pte_t *)gstage->pgd;
-	pte_t *ptep = &next_ptep[gstage_pte_index(map->addr, current_level)];
+	pte_t *ptep = &next_ptep[gstage_pte_index(gstage, map->addr, current_level)];
 
 	if (current_level < map->level)
 		return -EINVAL;
@@ -151,7 +153,7 @@ int kvm_riscv_gstage_set_pte(struct kvm_gstage *gstage,
 		}
 
 		current_level--;
-		ptep = &next_ptep[gstage_pte_index(map->addr, current_level)];
+		ptep = &next_ptep[gstage_pte_index(gstage, map->addr, current_level)];
 	}
 
 	if (pte_val(*ptep) != pte_val(map->pte)) {
@@ -175,7 +177,7 @@ int kvm_riscv_gstage_map_page(struct kvm_gstage *gstage,
 	out_map->addr = gpa;
 	out_map->level = 0;
 
-	ret = gstage_page_size_to_level(page_size, &out_map->level);
+	ret = gstage_page_size_to_level(gstage, page_size, &out_map->level);
 	if (ret)
 		return ret;
 
@@ -217,7 +219,7 @@ void kvm_riscv_gstage_op_pte(struct kvm_gstage *gstage, gpa_t addr,
 	u32 next_ptep_level;
 	unsigned long next_page_size, page_size;
 
-	ret = gstage_level_to_page_size(ptep_level, &page_size);
+	ret = gstage_level_to_page_size(gstage, ptep_level, &page_size);
 	if (ret)
 		return;
 
@@ -229,7 +231,7 @@ void kvm_riscv_gstage_op_pte(struct kvm_gstage *gstage, gpa_t addr,
 	if (ptep_level && !gstage_pte_leaf(ptep)) {
 		next_ptep = (pte_t *)gstage_pte_page_vaddr(ptep_get(ptep));
 		next_ptep_level = ptep_level - 1;
-		ret = gstage_level_to_page_size(next_ptep_level, &next_page_size);
+		ret = gstage_level_to_page_size(gstage, next_ptep_level, &next_page_size);
 		if (ret)
 			return;
 
@@ -263,7 +265,7 @@ void kvm_riscv_gstage_unmap_range(struct kvm_gstage *gstage,
 
 	while (addr < end) {
 		found_leaf = kvm_riscv_gstage_get_leaf(gstage, addr, &ptep, &ptep_level);
-		ret = gstage_level_to_page_size(ptep_level, &page_size);
+		ret = gstage_level_to_page_size(gstage, ptep_level, &page_size);
 		if (ret)
 			break;
 
@@ -297,7 +299,7 @@ void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
 
 	while (addr < end) {
 		found_leaf = kvm_riscv_gstage_get_leaf(gstage, addr, &ptep, &ptep_level);
-		ret = gstage_level_to_page_size(ptep_level, &page_size);
+		ret = gstage_level_to_page_size(gstage, ptep_level, &page_size);
 		if (ret)
 			break;
 
@@ -319,39 +321,34 @@ void __init kvm_riscv_gstage_mode_detect(void)
 	/* Try Sv57x4 G-stage mode */
 	csr_write(CSR_HGATP, HGATP_MODE_SV57X4 << HGATP_MODE_SHIFT);
 	if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == HGATP_MODE_SV57X4) {
-		kvm_riscv_gstage_mode = HGATP_MODE_SV57X4;
-		kvm_riscv_gstage_pgd_levels = 5;
+		kvm_riscv_gstage_max_pgd_levels = 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) == HGATP_MODE_SV48X4) {
-		kvm_riscv_gstage_mode = HGATP_MODE_SV48X4;
-		kvm_riscv_gstage_pgd_levels = 4;
+		kvm_riscv_gstage_max_pgd_levels = 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) == HGATP_MODE_SV39X4) {
-		kvm_riscv_gstage_mode = HGATP_MODE_SV39X4;
-		kvm_riscv_gstage_pgd_levels = 3;
+		kvm_riscv_gstage_max_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;
+		kvm_riscv_gstage_max_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;
+	kvm_riscv_gstage_max_pgd_levels = 0;
 
 done:
 	csr_write(CSR_HGATP, 0);
diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index 0f3fe3986fc0..90ee0a032b9a 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -105,17 +105,17 @@ static int __init riscv_kvm_init(void)
 		return rc;
 
 	kvm_riscv_gstage_mode_detect();
-	switch (kvm_riscv_gstage_mode) {
-	case HGATP_MODE_SV32X4:
+	switch (kvm_riscv_gstage_max_pgd_levels) {
+	case 2:
 		str = "Sv32x4";
 		break;
-	case HGATP_MODE_SV39X4:
+	case 3:
 		str = "Sv39x4";
 		break;
-	case HGATP_MODE_SV48X4:
+	case 4:
 		str = "Sv48x4";
 		break;
-	case HGATP_MODE_SV57X4:
+	case 5:
 		str = "Sv57x4";
 		break;
 	default:
@@ -164,7 +164,7 @@ static int __init riscv_kvm_init(void)
 			 (rc) ? slist : "no features");
 	}
 
-	kvm_info("using %s G-stage page table format\n", str);
+	kvm_info("highest G-stage page table mode is %s\n", str);
 
 	kvm_info("VMID %ld bits available\n", kvm_riscv_gstage_vmid_bits());
 
diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 088d33ba90ed..fbcdd75cb9af 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -67,7 +67,7 @@ int kvm_riscv_mmu_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
 		if (!writable)
 			map.pte = pte_wrprotect(map.pte);
 
-		ret = kvm_mmu_topup_memory_cache(&pcache, kvm_riscv_gstage_pgd_levels);
+		ret = kvm_mmu_topup_memory_cache(&pcache, kvm->arch.pgd_levels);
 		if (ret)
 			goto out;
 
@@ -186,7 +186,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	 * space addressable by the KVM guest GPA space.
 	 */
 	if ((new->base_gfn + new->npages) >=
-	    (kvm_riscv_gstage_gpa_size >> PAGE_SHIFT))
+	     kvm_riscv_gstage_gpa_size(kvm->arch.pgd_levels) >> PAGE_SHIFT)
 		return -EFAULT;
 
 	hva = new->userspace_addr;
@@ -472,7 +472,7 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 	memset(out_map, 0, sizeof(*out_map));
 
 	/* We need minimum second+third level pages */
-	ret = kvm_mmu_topup_memory_cache(pcache, kvm_riscv_gstage_pgd_levels);
+	ret = kvm_mmu_topup_memory_cache(pcache, kvm->arch.pgd_levels);
 	if (ret) {
 		kvm_err("Failed to topup G-stage cache\n");
 		return ret;
@@ -575,6 +575,7 @@ int kvm_riscv_mmu_alloc_pgd(struct kvm *kvm)
 		return -ENOMEM;
 	kvm->arch.pgd = page_to_virt(pgd_page);
 	kvm->arch.pgd_phys = page_to_phys(pgd_page);
+	kvm->arch.pgd_levels = kvm_riscv_gstage_max_pgd_levels;
 
 	return 0;
 }
@@ -590,10 +591,12 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm)
 		gstage.flags = 0;
 		gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
 		gstage.pgd = kvm->arch.pgd;
-		kvm_riscv_gstage_unmap_range(&gstage, 0UL, kvm_riscv_gstage_gpa_size, false);
+		kvm_riscv_gstage_unmap_range(&gstage, 0UL,
+			kvm_riscv_gstage_gpa_size(kvm->arch.pgd_levels), false);
 		pgd = READ_ONCE(kvm->arch.pgd);
 		kvm->arch.pgd = NULL;
 		kvm->arch.pgd_phys = 0;
+		kvm->arch.pgd_levels = 0;
 	}
 	spin_unlock(&kvm->mmu_lock);
 
@@ -603,11 +606,12 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm)
 
 void kvm_riscv_mmu_update_hgatp(struct kvm_vcpu *vcpu)
 {
-	unsigned long hgatp = kvm_riscv_gstage_mode << HGATP_MODE_SHIFT;
-	struct kvm_arch *k = &vcpu->kvm->arch;
+	struct kvm_arch *ka = &vcpu->kvm->arch;
+	unsigned long hgatp = kvm_riscv_gstage_mode(ka->pgd_levels)
+			      << HGATP_MODE_SHIFT;
 
-	hgatp |= (READ_ONCE(k->vmid.vmid) << HGATP_VMID_SHIFT) & HGATP_VMID;
-	hgatp |= (k->pgd_phys >> PAGE_SHIFT) & HGATP_PPN;
+	hgatp |= (READ_ONCE(ka->vmid.vmid) << HGATP_VMID_SHIFT) & HGATP_VMID;
+	hgatp |= (ka->pgd_phys >> PAGE_SHIFT) & HGATP_PPN;
 
 	ncsr_write(CSR_HGATP, hgatp);
 
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 13c63ae1a78b..4d82a886102c 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -199,7 +199,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = KVM_USER_MEM_SLOTS;
 		break;
 	case KVM_CAP_VM_GPA_BITS:
-		r = kvm_riscv_gstage_gpa_bits;
+		r = kvm_riscv_gstage_gpa_bits(kvm->arch.pgd_levels);
 		break;
 	default:
 		r = 0;
diff --git a/arch/riscv/kvm/vmid.c b/arch/riscv/kvm/vmid.c
index cf34d448289d..c15bdb1dd8be 100644
--- a/arch/riscv/kvm/vmid.c
+++ b/arch/riscv/kvm/vmid.c
@@ -26,7 +26,8 @@ static DEFINE_SPINLOCK(vmid_lock);
 void __init kvm_riscv_gstage_vmid_detect(void)
 {
 	/* Figure-out number of VMID bits in HW */
-	csr_write(CSR_HGATP, (kvm_riscv_gstage_mode << HGATP_MODE_SHIFT) | HGATP_VMID);
+	csr_write(CSR_HGATP, (kvm_riscv_gstage_mode(kvm_riscv_gstage_max_pgd_levels) <<
+			      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);
-- 
2.50.1

[PATCH v6 2/4] RISC-V: KVM: Cache gstage pgd_levels in struct kvm_gstage

[fangyu.yu]

From: Fangyu Yu <fangyu.yu@linux.alibaba.com>

Gstage page-table helpers frequently chase gstage->kvm->arch to
fetch pgd_levels. This adds noise and repeats the same dereference
chain in hot paths.

Add pgd_levels to struct kvm_gstage and initialize it from kvm->arch
when setting up a gstage instance. Introduce kvm_riscv_gstage_init()
to centralize initialization and switch gstage code to use
gstage->pgd_levels.

Suggested-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
---
 arch/riscv/include/asm/kvm_gstage.h | 10 ++++++
 arch/riscv/kvm/gstage.c             | 10 +++---
 arch/riscv/kvm/mmu.c                | 50 ++++++-----------------------
 3 files changed, 25 insertions(+), 45 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_gstage.h b/arch/riscv/include/asm/kvm_gstage.h
index 5aa58d1f692a..70d9d483365e 100644
--- a/arch/riscv/include/asm/kvm_gstage.h
+++ b/arch/riscv/include/asm/kvm_gstage.h
@@ -15,6 +15,7 @@ struct kvm_gstage {
 #define KVM_GSTAGE_FLAGS_LOCAL		BIT(0)
 	unsigned long vmid;
 	pgd_t *pgd;
+	unsigned long pgd_levels;
 };
 
 struct kvm_gstage_mapping {
@@ -92,4 +93,13 @@ static inline unsigned long kvm_riscv_gstage_mode(unsigned long pgd_levels)
 	}
 }
 
+static inline void kvm_riscv_gstage_init(struct kvm_gstage *gstage, struct kvm *kvm)
+{
+	gstage->kvm = kvm;
+	gstage->flags = 0;
+	gstage->vmid = READ_ONCE(kvm->arch.vmid.vmid);
+	gstage->pgd = kvm->arch.pgd;
+	gstage->pgd_levels = kvm->arch.pgd_levels;
+}
+
 #endif
diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index 4beb9322fe76..7c4c34bc191b 100644
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -26,7 +26,7 @@ static inline unsigned long gstage_pte_index(struct kvm_gstage *gstage,
 	unsigned long mask;
 	unsigned long shift = HGATP_PAGE_SHIFT + (kvm_riscv_gstage_index_bits * level);
 
-	if (level == gstage->kvm->arch.pgd_levels - 1)
+	if (level == gstage->pgd_levels - 1)
 		mask = (PTRS_PER_PTE * (1UL << kvm_riscv_gstage_pgd_xbits)) - 1;
 	else
 		mask = PTRS_PER_PTE - 1;
@@ -45,7 +45,7 @@ static int gstage_page_size_to_level(struct kvm_gstage *gstage, unsigned long pa
 	u32 i;
 	unsigned long psz = 1UL << 12;
 
-	for (i = 0; i < gstage->kvm->arch.pgd_levels; i++) {
+	for (i = 0; i < gstage->pgd_levels; i++) {
 		if (page_size == (psz << (i * kvm_riscv_gstage_index_bits))) {
 			*out_level = i;
 			return 0;
@@ -58,7 +58,7 @@ static int gstage_page_size_to_level(struct kvm_gstage *gstage, unsigned long pa
 static int gstage_level_to_page_order(struct kvm_gstage *gstage, u32 level,
 				      unsigned long *out_pgorder)
 {
-	if (gstage->kvm->arch.pgd_levels < level)
+	if (gstage->pgd_levels < level)
 		return -EINVAL;
 
 	*out_pgorder = 12 + (level * kvm_riscv_gstage_index_bits);
@@ -83,7 +83,7 @@ bool kvm_riscv_gstage_get_leaf(struct kvm_gstage *gstage, gpa_t addr,
 			       pte_t **ptepp, u32 *ptep_level)
 {
 	pte_t *ptep;
-	u32 current_level = gstage->kvm->arch.pgd_levels - 1;
+	u32 current_level = gstage->pgd_levels - 1;
 
 	*ptep_level = current_level;
 	ptep = (pte_t *)gstage->pgd;
@@ -127,7 +127,7 @@ int kvm_riscv_gstage_set_pte(struct kvm_gstage *gstage,
 			     struct kvm_mmu_memory_cache *pcache,
 			     const struct kvm_gstage_mapping *map)
 {
-	u32 current_level = gstage->kvm->arch.pgd_levels - 1;
+	u32 current_level = gstage->pgd_levels - 1;
 	pte_t *next_ptep = (pte_t *)gstage->pgd;
 	pte_t *ptep = &next_ptep[gstage_pte_index(gstage, map->addr, current_level)];
 
diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index fbcdd75cb9af..2d3def024270 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -24,10 +24,7 @@ static void mmu_wp_memory_region(struct kvm *kvm, int slot)
 	phys_addr_t end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;
 	struct kvm_gstage gstage;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 
 	spin_lock(&kvm->mmu_lock);
 	kvm_riscv_gstage_wp_range(&gstage, start, end);
@@ -49,10 +46,7 @@ int kvm_riscv_mmu_ioremap(struct kvm *kvm, gpa_t gpa, phys_addr_t hpa,
 	struct kvm_gstage_mapping map;
 	struct kvm_gstage gstage;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 
 	end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
 	pfn = __phys_to_pfn(hpa);
@@ -89,10 +83,7 @@ void kvm_riscv_mmu_iounmap(struct kvm *kvm, gpa_t gpa, unsigned long size)
 {
 	struct kvm_gstage gstage;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 
 	spin_lock(&kvm->mmu_lock);
 	kvm_riscv_gstage_unmap_range(&gstage, gpa, size, false);
@@ -109,10 +100,7 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
 	phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
 	struct kvm_gstage gstage;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 
 	kvm_riscv_gstage_wp_range(&gstage, start, end);
 }
@@ -141,10 +129,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
 	phys_addr_t size = slot->npages << PAGE_SHIFT;
 	struct kvm_gstage gstage;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 
 	spin_lock(&kvm->mmu_lock);
 	kvm_riscv_gstage_unmap_range(&gstage, gpa, size, false);
@@ -250,10 +235,7 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
 	if (!kvm->arch.pgd)
 		return false;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 	mmu_locked = spin_trylock(&kvm->mmu_lock);
 	kvm_riscv_gstage_unmap_range(&gstage, range->start << PAGE_SHIFT,
 				     (range->end - range->start) << PAGE_SHIFT,
@@ -275,10 +257,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 
 	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 	if (!kvm_riscv_gstage_get_leaf(&gstage, range->start << PAGE_SHIFT,
 				       &ptep, &ptep_level))
 		return false;
@@ -298,10 +277,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 
 	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 	if (!kvm_riscv_gstage_get_leaf(&gstage, range->start << PAGE_SHIFT,
 				       &ptep, &ptep_level))
 		return false;
@@ -463,10 +439,7 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 	struct kvm_gstage gstage;
 	struct page *page;
 
-	gstage.kvm = kvm;
-	gstage.flags = 0;
-	gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-	gstage.pgd = kvm->arch.pgd;
+	kvm_riscv_gstage_init(&gstage, kvm);
 
 	/* Setup initial state of output mapping */
 	memset(out_map, 0, sizeof(*out_map));
@@ -587,10 +560,7 @@ void kvm_riscv_mmu_free_pgd(struct kvm *kvm)
 
 	spin_lock(&kvm->mmu_lock);
 	if (kvm->arch.pgd) {
-		gstage.kvm = kvm;
-		gstage.flags = 0;
-		gstage.vmid = READ_ONCE(kvm->arch.vmid.vmid);
-		gstage.pgd = kvm->arch.pgd;
+		kvm_riscv_gstage_init(&gstage, kvm);
 		kvm_riscv_gstage_unmap_range(&gstage, 0UL,
 			kvm_riscv_gstage_gpa_size(kvm->arch.pgd_levels), false);
 		pgd = READ_ONCE(kvm->arch.pgd);
-- 
2.50.1

[PATCH v6 3/4] RISC-V: KVM: Detect and expose supported HGATP G-stage modes

[fangyu.yu]

From: Fangyu Yu <fangyu.yu@linux.alibaba.com>

Extend kvm_riscv_gstage_mode_detect() to probe all HGATP.MODE values
supported by the host and record them in a bitmask. Keep tracking the
maximum supported G-stage page table level for existing internal users.

Also provide lightweight helpers to retrieve the supported-mode bitmask
and validate a requested HGATP.MODE against it.

Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
---
 arch/riscv/include/asm/kvm_gstage.h | 11 ++++++++
 arch/riscv/kvm/gstage.c             | 43 +++++++++++++++--------------
 2 files changed, 34 insertions(+), 20 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_gstage.h b/arch/riscv/include/asm/kvm_gstage.h
index 70d9d483365e..bbf8f45c6563 100644
--- a/arch/riscv/include/asm/kvm_gstage.h
+++ b/arch/riscv/include/asm/kvm_gstage.h
@@ -31,6 +31,7 @@ struct kvm_gstage_mapping {
 #endif
 
 extern unsigned long kvm_riscv_gstage_max_pgd_levels;
+extern u32 kvm_riscv_gstage_supported_mode_mask;
 
 #define kvm_riscv_gstage_pgd_xbits	2
 #define kvm_riscv_gstage_pgd_size	(1UL << (HGATP_PAGE_SHIFT + kvm_riscv_gstage_pgd_xbits))
@@ -102,4 +103,14 @@ static inline void kvm_riscv_gstage_init(struct kvm_gstage *gstage, struct kvm *
 	gstage->pgd_levels = kvm->arch.pgd_levels;
 }
 
+static inline u32 kvm_riscv_get_hgatp_mode_mask(void)
+{
+	return kvm_riscv_gstage_supported_mode_mask;
+}
+
+static inline bool kvm_riscv_hgatp_mode_is_valid(unsigned long mode)
+{
+	return kvm_riscv_gstage_supported_mode_mask & BIT(mode);
+}
+
 #endif
diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index 7c4c34bc191b..459041255c14 100644
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -16,6 +16,8 @@ unsigned long kvm_riscv_gstage_max_pgd_levels __ro_after_init = 3;
 #else
 unsigned long kvm_riscv_gstage_max_pgd_levels __ro_after_init = 2;
 #endif
+/* Bitmask of supported HGATP.MODE encodings (BIT(HGATP_MODE_*)). */
+u32 kvm_riscv_gstage_supported_mode_mask __ro_after_init;
 
 #define gstage_pte_leaf(__ptep)	\
 	(pte_val(*(__ptep)) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC))
@@ -315,42 +317,43 @@ void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
 	}
 }
 
+static bool __init kvm_riscv_hgatp_mode_supported(unsigned long mode)
+{
+	csr_write(CSR_HGATP, mode << HGATP_MODE_SHIFT);
+	return ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == mode);
+}
+
 void __init kvm_riscv_gstage_mode_detect(void)
 {
+	kvm_riscv_gstage_supported_mode_mask = 0;
+	kvm_riscv_gstage_max_pgd_levels = 0;
+
 #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) == HGATP_MODE_SV57X4) {
-		kvm_riscv_gstage_max_pgd_levels = 5;
-		goto done;
+	/* Try Sv39x4 G-stage mode */
+	if (kvm_riscv_hgatp_mode_supported(HGATP_MODE_SV39X4)) {
+		kvm_riscv_gstage_supported_mode_mask |= BIT(HGATP_MODE_SV39X4);
+		kvm_riscv_gstage_max_pgd_levels = 3;
 	}
 
 	/* Try Sv48x4 G-stage mode */
-	csr_write(CSR_HGATP, HGATP_MODE_SV48X4 << HGATP_MODE_SHIFT);
-	if ((csr_read(CSR_HGATP) >> HGATP_MODE_SHIFT) == HGATP_MODE_SV48X4) {
+	if (kvm_riscv_hgatp_mode_supported(HGATP_MODE_SV48X4)) {
+		kvm_riscv_gstage_supported_mode_mask |= BIT(HGATP_MODE_SV48X4);
 		kvm_riscv_gstage_max_pgd_levels = 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) == HGATP_MODE_SV39X4) {
-		kvm_riscv_gstage_max_pgd_levels = 3;
-		goto done;
+	/* Try Sv57x4 G-stage mode */
+	if (kvm_riscv_hgatp_mode_supported(HGATP_MODE_SV57X4)) {
+		kvm_riscv_gstage_supported_mode_mask |= BIT(HGATP_MODE_SV57X4);
+		kvm_riscv_gstage_max_pgd_levels = 5;
 	}
 #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) {
+	if (kvm_riscv_hgatp_mode_supported(HGATP_MODE_SV32X4)) {
+		kvm_riscv_gstage_supported_mode_mask |= BIT(HGATP_MODE_SV32X4);
 		kvm_riscv_gstage_max_pgd_levels = 2;
-		goto done;
 	}
 #endif
 
-	/* KVM depends on !HGATP_MODE_OFF */
-	kvm_riscv_gstage_max_pgd_levels = 0;
-
-done:
 	csr_write(CSR_HGATP, 0);
 	kvm_riscv_local_hfence_gvma_all();
 }
-- 
2.50.1

[PATCH v6 4/4] RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE

[fangyu.yu]

From: Fangyu Yu <fangyu.yu@linux.alibaba.com>

Add a VM capability that allows userspace to select the G-stage page table
format by setting HGATP.MODE on a per-VM basis.

Userspace enables the capability via KVM_ENABLE_CAP, passing the requested
HGATP.MODE in args[0]. The request is rejected with -EINVAL if the mode is
not supported by the host, and with -EBUSY if the VM has already been
committed (e.g. vCPUs have been created or any memslot is populated).

KVM_CHECK_EXTENSION(KVM_CAP_RISCV_SET_HGATP_MODE) returns a bitmask of the
HGATP.MODE formats supported by the host.

Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
---
 Documentation/virt/kvm/api.rst | 27 +++++++++++++++++++++++++++
 arch/riscv/kvm/vm.c            | 18 ++++++++++++++++--
 include/uapi/linux/kvm.h       |  1 +
 3 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 032516783e96..9d7f6958fa81 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8902,6 +8902,33 @@ helpful if user space wants to emulate instructions which are not
 This capability can be enabled dynamically even if VCPUs were already
 created and are running.
 
+7.47 KVM_CAP_RISCV_SET_HGATP_MODE
+---------------------------------
+
+:Architectures: riscv
+:Type: VM
+:Parameters: args[0] contains the requested HGATP mode
+:Returns:
+  - 0 on success.
+  - -EINVAL if args[0] is outside the range of HGATP modes supported by the
+    hardware.
+  - -EBUSY if vCPUs have already been created for the VM, if the VM has any
+    non-empty memslots.
+
+This capability allows userspace to explicitly select the HGATP mode for
+the VM. The selected mode must be supported by both KVM and hardware. This
+capability must be enabled before creating any vCPUs or memslots.
+
+If this capability is not enabled, KVM will select the default HGATP mode
+automatically. The default is the highest HGATP.MODE value supported by
+hardware.
+
+``KVM_CHECK_EXTENSION(KVM_CAP_RISCV_SET_HGATP_MODE)`` returns a bitmask of
+HGATP.MODE values supported by the host. A return value of 0 indicates that
+the capability is not supported. Supported-mode bitmask use HGATP.MODE
+encodings as defined by the RISC-V privileged specification, such as Sv39x4
+corresponds to HGATP.MODE=8, so userspace should test bitmask & BIT(8).
+
 8. Other capabilities.
 ======================
 
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 4d82a886102c..5e82a3ad3ad0 100644
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -201,6 +201,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_VM_GPA_BITS:
 		r = kvm_riscv_gstage_gpa_bits(kvm->arch.pgd_levels);
 		break;
+	case KVM_CAP_RISCV_SET_HGATP_MODE:
+		r = kvm_riscv_get_hgatp_mode_mask();
+		break;
 	default:
 		r = 0;
 		break;
@@ -211,12 +214,23 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 
 int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 {
+	if (cap->flags)
+		return -EINVAL;
+
 	switch (cap->cap) {
 	case KVM_CAP_RISCV_MP_STATE_RESET:
-		if (cap->flags)
-			return -EINVAL;
 		kvm->arch.mp_state_reset = true;
 		return 0;
+	case KVM_CAP_RISCV_SET_HGATP_MODE:
+		if (!kvm_riscv_hgatp_mode_is_valid(cap->args[0]))
+			return -EINVAL;
+
+		if (kvm->created_vcpus || !kvm_are_all_memslots_empty(kvm))
+			return -EBUSY;
+#ifdef CONFIG_64BIT
+		kvm->arch.pgd_levels = 3 + cap->args[0] - HGATP_MODE_SV39X4;
+#endif
+		return 0;
 	default:
 		return -EINVAL;
 	}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 80364d4dbebb..a74a80fd4046 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -989,6 +989,7 @@ struct kvm_enable_cap {
 #define KVM_CAP_ARM_SEA_TO_USER 245
 #define KVM_CAP_S390_USER_OPEREXEC 246
 #define KVM_CAP_S390_KEYOP 247
+#define KVM_CAP_RISCV_SET_HGATP_MODE 248
 
 struct kvm_irq_routing_irqchip {
 	__u32 irqchip;
-- 
2.50.1