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Thu, 12 Jun 2025 23:58:17 -0700 (PDT) From: Anup Patel To: Atish Patra Cc: Palmer Dabbelt , Paul Walmsley , Alexandre Ghiti , Andrew Jones , Anup Patel , kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Anup Patel Subject: [PATCH v2 05/12] RISC-V: KVM: Don't flush TLB when PTE is unchanged Date: Fri, 13 Jun 2025 12:27:36 +0530 Message-ID: <20250613065743.737102-6-apatel@ventanamicro.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250613065743.737102-1-apatel@ventanamicro.com> References: <20250613065743.737102-1-apatel@ventanamicro.com> 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 Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Atish Patra --- arch/riscv/kvm/mmu.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c index 1087ea74567b..29f1bd853a66 100644 --- a/arch/riscv/kvm/mmu.c +++ b/arch/riscv/kvm/mmu.c @@ -167,9 +167,11 @@ static int gstage_set_pte(struct kvm *kvm, u32 level, ptep =3D &next_ptep[gstage_pte_index(addr, current_level)]; } =20 - set_pte(ptep, *new_pte); - if (gstage_pte_leaf(ptep)) - gstage_remote_tlb_flush(kvm, current_level, addr); + if (pte_val(*ptep) !=3D pte_val(*new_pte)) { + set_pte(ptep, *new_pte); + if (gstage_pte_leaf(ptep)) + gstage_remote_tlb_flush(kvm, current_level, addr); + } =20 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; =20 @@ -258,11 +260,13 @@ static void gstage_op_pte(struct kvm *kvm, gpa_t addr, if (op =3D=3D GSTAGE_OP_CLEAR) put_page(virt_to_page(next_ptep)); } else { + old_pte =3D *ptep; if (op =3D=3D GSTAGE_OP_CLEAR) set_pte(ptep, __pte(0)); else if (op =3D=3D 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) !=3D pte_val(old_pte)) + gstage_remote_tlb_flush(kvm, ptep_level, addr); } } =20 --=20 2.43.0