Re: RISC-V: KVM: Fix hugepage mapping handling during dirty logging

[wang.yechao255]

> On Thu, Feb 26, 2026 at 2:52 PM <wang.yechao255@xxxxxxxxxx> wrote:

> >

> > From: Wang Yechao <wang.yechao255@xxxxxxxxxx>

> >

> > When dirty logging is enabled, the gstage page tables must be mapped

> > at PAGE_SIZE granularity to track dirty pages accurately. Currently,

> > if a huge PTE is encountered during the write-protect fault, the code

> > returns -EEXIST, which breaks VM migration.

> >

> > Instead of returning an error, drop the huge PTE and map only the page

> > that is currently being accessed. This on‑demand approach avoids the

> > overhead of splitting the entire huge page into small pages upfront.

> >

> > Signed-off-by: Wang Yechao <wang.yechao255@xxxxxxxxxx>

> > ---

> >  arch/riscv/kvm/gstage.c | 2 +-

> >  1 file changed, 1 insertion(+), 1 deletion(-)

> >

> > diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c

> > index b67d60d722c2..16c8afdafbfb 100644

> > --- a/arch/riscv/kvm/gstage.c

> > +++ b/arch/riscv/kvm/gstage.c

> > @@ -134,7 +134,7 @@ int kvm_riscv_gstage_set_pte(struct kvm_gstage *gstage,

> >

> >         while (current_level != map->level) {

> >                 if (gstage_pte_leaf(ptep))

> > -                       return -EEXIST;

> > +                       set_pte(ptep, __pte(0));

> 

> Making a leaf PTE invalid mut be followed by TLB invalidation

> using gstage_tlb_flush().

> 

Thank you for the review. You are right, I missed the required TLB invalidation.

> I think returning -EEXIST is the right thing to do here because

> caller has to split a huge PTE with proper TLB invalidation.

> 

> Regards,

> Anup

ok, let the caller split the huge PTE with proper TLB invalidation.

I will update the patch accordingly in the next version.

Regards,

Yechao