[PATCH v4 0/2] iommu/riscv: Support Svpbmt memory types in generic_pt

[PATCH v4 0/2] iommu/riscv: Support Svpbmt memory types in generic_pt

[fangyu.yu]

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

RISC-V Svpbmt adds page-based memory types (PBMT) to PTEs, allowing
mappings to be tagged as e.g. normal memory, non-cacheable memory, or
I/O.

This series wires the RISC-V IOMMU Svpbmt capability into generic_pt
and uses PBMT to encode device memory attributes for IOMMU mappings.

---
Changes in v4:
    - Fix build warning on 32-bit configurations by using BIT_ULL() for RISCVPT_NC and RISCVPT_IO. 
    - Link to v3:
      https://lore.kernel.org/linux-riscv/20260417140746.97817-1-fangyu.yu@linux.alibaba.com/
---
Changes in v3:
    - Include RISCVPT_NC and RISCVPT_IO in riscvpt_attr_from_entry()
      so iommupt KUnit tests preserve these descriptor bits..
    - Link to v2:
      https://lore.kernel.org/linux-riscv/20260414110212.79526-1-fangyu.yu@linux.alibaba.com
---
Changes in v2:
    - Add a comment for PT_FEAT_RISCV_SVPBMT (per Kevin and Jason).
    - Clarify PBMT encoding condition, sort PBMT-related bits by
      position, and drop the redundant PBMT clear(per Kevin).
    - Link to v1:
      https://lore.kernel.org/linux-iommu/20260411022223.91029-1-fangyu.yu@linux.alibaba.com/

Fangyu Yu (2):
  iommu/riscv: Advertise Svpbmt support to generic page table
  iommupt: Encode IOMMU_MMIO/IOMMU_CACHE via RISC-V Svpbmt bits

 drivers/iommu/generic_pt/fmt/riscv.h | 11 ++++++++++-
 drivers/iommu/riscv/iommu.c          |  2 ++
 include/linux/generic_pt/common.h    |  4 ++++
 3 files changed, 16 insertions(+), 1 deletion(-)

-- 
2.50.1

[PATCH v4 1/2] iommu/riscv: Advertise Svpbmt support to generic page table

[fangyu.yu]

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

The RISC-V IOMMU can optionally support Svpbmt page-based memory types
in its page table format. When present,the generic page table code can
use this capability to encode memory attributes (e.g. MMIO vs normal
memory) in PTEs.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
---
 drivers/iommu/riscv/iommu.c       | 2 ++
 include/linux/generic_pt/common.h | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index a31f50bbad35..6c324f9fdc53 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -1268,6 +1268,8 @@ static struct iommu_domain *riscv_iommu_alloc_paging_domain(struct device *dev)
 	cfg.common.features = BIT(PT_FEAT_SIGN_EXTEND) |
 			      BIT(PT_FEAT_FLUSH_RANGE) |
 			      BIT(PT_FEAT_RISCV_SVNAPOT_64K);
+	if (iommu->caps & RISCV_IOMMU_CAPABILITIES_SVPBMT)
+		cfg.common.features |= BIT(PT_FEAT_RISCV_SVPBMT);
 	domain->riscvpt.iommu.nid = dev_to_node(iommu->dev);
 	domain->domain.ops = &riscv_iommu_paging_domain_ops;
 
diff --git a/include/linux/generic_pt/common.h b/include/linux/generic_pt/common.h
index fc5d0b5edadc..2683e5b38998 100644
--- a/include/linux/generic_pt/common.h
+++ b/include/linux/generic_pt/common.h
@@ -188,6 +188,10 @@ enum {
 	 * Support the 64k contiguous page size following the Svnapot extension.
 	 */
 	PT_FEAT_RISCV_SVNAPOT_64K = PT_FEAT_FMT_START,
+	/*
+	 * Support Svpbmt extension: encode page-based memory type (PBMT) in PTEs.
+	 */
+	PT_FEAT_RISCV_SVPBMT,
 
 };
 
-- 
2.50.1

[PATCH v4 2/2] iommupt: Encode IOMMU_MMIO/IOMMU_CACHE via RISC-V Svpbmt bits

[fangyu.yu]

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

When the RISC-V IOMMU page table format support Svpbmt, PBMT provides
a way to tag mappings with page-based memory types. Encode memory type
via PBMT in RISC-V IOMMU PTEs:

  - IOMMU_MMIO   -> PBMT=IO
  - !IOMMU_MMIO && !IOMMU_CACHE -> PBMT=NC
  - otherwise    -> PBMT=Normal (PBMT=0)

Only touch PBMT when PT_FEAT_RISCV_SVPBMT is advertised.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
---
 drivers/iommu/generic_pt/fmt/riscv.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/generic_pt/fmt/riscv.h b/drivers/iommu/generic_pt/fmt/riscv.h
index a7fef6266a36..ae9a76514416 100644
--- a/drivers/iommu/generic_pt/fmt/riscv.h
+++ b/drivers/iommu/generic_pt/fmt/riscv.h
@@ -64,6 +64,8 @@ enum {
 	RISCVPT_PPN64 = GENMASK_ULL(53, 10),
 	RISCVPT_PPN64_64K = GENMASK_ULL(53, 14),
 	RISCVPT_PBMT = GENMASK_ULL(62, 61),
+	RISCVPT_NC = BIT_ULL(61),
+	RISCVPT_IO = BIT_ULL(62),
 	RISCVPT_N = BIT_ULL(63),
 
 	/* Svnapot encodings for ppn[0] */
@@ -201,7 +203,8 @@ static inline void riscvpt_attr_from_entry(const struct pt_state *pts,
 {
 	attrs->descriptor_bits =
 		pts->entry & (RISCVPT_R | RISCVPT_W | RISCVPT_X | RISCVPT_U |
-			      RISCVPT_G | RISCVPT_A | RISCVPT_D);
+			      RISCVPT_G | RISCVPT_A | RISCVPT_D | RISCVPT_NC |
+			      RISCVPT_IO);
 }
 #define pt_attr_from_entry riscvpt_attr_from_entry
 
@@ -237,6 +240,12 @@ static inline int riscvpt_iommu_set_prot(struct pt_common *common,
 		pte |= RISCVPT_R;
 	if (!(iommu_prot & IOMMU_NOEXEC))
 		pte |= RISCVPT_X;
+	if (common->features & BIT(PT_FEAT_RISCV_SVPBMT)) {
+		if (iommu_prot & IOMMU_MMIO)
+			pte |= RISCVPT_IO;
+		else if (!(iommu_prot & IOMMU_CACHE))
+			pte |= RISCVPT_NC;
+	}
 
 	/* Caller must specify a supported combination of flags */
 	if (unlikely((pte & (RISCVPT_X | RISCVPT_W | RISCVPT_R)) == 0))
-- 
2.50.1

Re: [PATCH v4 0/2] iommu/riscv: Support Svpbmt memory types in generic_pt

[Jörg Rödel]

On Tue, May 12, 2026 at 03:41:40PM +0800, fangyu.yu@linux.alibaba.com wrote:
> Changes in v4:
>     - Fix build warning on 32-bit configurations by using BIT_ULL() for RISCVPT_NC and RISCVPT_IO. 
>     - Link to v3:
>       https://lore.kernel.org/linux-riscv/20260417140746.97817-1-fangyu.yu@linux.alibaba.com/

Please send this as a diff to the patches which are already in the IOMMU tree.

-Joerg

Re: Re: [PATCH v4 0/2] iommu/riscv: Support Svpbmt memory types in generic_pt

[fangyu.yu]

>> Changes in v4:
>>     - Fix build warning on 32-bit configurations by using BIT_ULL() for RISCVPT_NC and RISCVPT_IO.
>>     - Link to v3:
>>       https://lore.kernel.org/linux-riscv/20260417140746.97817-1-fangyu.yu@linux.alibaba.com/
>
>Please send this as a diff to the patches which are already in the IOMMU tree.
>

Hi Joerg,

Thanks, I’ll resend the fixup diff [1] based on the current IOMMU tree `riscv` branch.

[1] https://lore.kernel.org/linux-riscv/20260512144330.91113-1-fangyu.yu@linux.alibaba.com/

Thanks,
Fangyu

>-Joerg