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RISC-V: KVM: Don't flush TLB when PTE is unchanged

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The gstage_set_pte() and gstage_op_pte() should flush TLB only when
a leaf PTE changes so that unnecessary TLB flushes can be avoided.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-6-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Anup Patel 2025-06-18 17:05:25 +05:30 committed by Anup Patel
parent 7584eb611e
commit eaa98ba20b
1 changed files with 9 additions and 5 deletions
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14
arch/riscv/kvm/mmu.c
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@ -167,9 +167,11 @@ static int gstage_set_pte(struct kvm *kvm, u32 level,
ptep = &next_ptep[gstage_pte_index(addr, current_level)];
}
set_pte(ptep, *new_pte);
if (gstage_pte_leaf(ptep))
gstage_remote_tlb_flush(kvm, current_level, addr);
if (pte_val(*ptep) != pte_val(*new_pte)) {
set_pte(ptep, *new_pte);
if (gstage_pte_leaf(ptep))
gstage_remote_tlb_flush(kvm, current_level, addr);
}
return 0;
}
@ -229,7 +231,7 @@ static void gstage_op_pte(struct kvm *kvm, gpa_t addr,
pte_t *ptep, u32 ptep_level, enum gstage_op op)
{
int i, ret;
pte_t *next_ptep;
pte_t old_pte, *next_ptep;
u32 next_ptep_level;
unsigned long next_page_size, page_size;
@ -258,11 +260,13 @@ static void gstage_op_pte(struct kvm *kvm, gpa_t addr,
if (op == GSTAGE_OP_CLEAR)
put_page(virt_to_page(next_ptep));
} else {
old_pte = *ptep;
if (op == GSTAGE_OP_CLEAR)
set_pte(ptep, __pte(0));
else if (op == GSTAGE_OP_WP)
set_pte(ptep, __pte(pte_val(ptep_get(ptep)) & ~_PAGE_WRITE));
gstage_remote_tlb_flush(kvm, ptep_level, addr);
if (pte_val(*ptep) != pte_val(old_pte))
gstage_remote_tlb_flush(kvm, ptep_level, addr);
}
}