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Wed, 01 Jul 2026 00:53:00 -0700 (PDT) Received: from wud.bbrouter ([2409:8a1e:9473:9f10:5de9:783b:c249:18c5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8479ff8f959sm3608232b3a.3.2026.07.01.00.52.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jul 2026 00:53:00 -0700 (PDT) From: "Dylan.Wu" To: anup@brainfault.org, palmer@dabbelt.com Cc: atish.patra@linux.dev, pjw@kernel.org, aou@eecs.berkeley.edu, alex@ghiti.fr, zhouquan@iscas.ac.cn, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, "Dylan.Wu" Subject: [PATCH] riscv: kvm: Skip preventive hfence.gvma for new G-stage mappings with Svvptc Date: Wed, 1 Jul 2026 03:52:39 -0400 Message-Id: <20260701075239.95542-1-fredwudi0305@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit For Invalid->Valid G-stage leaf PTE updates, the flush in kvm_riscv_gstage_set_pte() is preventive. When Svvptc is available, new valid PTEs become visible to the page-table walker within a bounded time, so an immediate hfence.gvma is unnecessary. Skip gstage_tlb_flush() for that case. Permission-restricting updates continue to use the existing flush path. Assisted-by: YuanSheng: deepseek-v4-pro Co-developed-by: Quan Zhou Signed-off-by: Quan Zhou Signed-off-by: Dylan.Wu --- arch/riscv/kvm/gstage.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c index c4c3b7956..7b805112d 100644 --- a/arch/riscv/kvm/gstage.c +++ b/arch/riscv/kvm/gstage.c @@ -10,6 +10,8 @@ #include #include #include +#include +#include #ifdef CONFIG_64BIT unsigned long kvm_riscv_gstage_max_pgd_levels __ro_after_init = 3; @@ -171,8 +173,11 @@ int kvm_riscv_gstage_set_pte(struct kvm_gstage *gstage, } if (pte_val(*ptep) != pte_val(map->pte)) { + bool was_invalid = !pte_val(*ptep); set_pte(ptep, map->pte); - if (gstage_pte_leaf(ptep)) + if (gstage_pte_leaf(ptep) && + !(was_invalid && + riscv_has_extension_unlikely(RISCV_ISA_EXT_SVVPTC))) gstage_tlb_flush(gstage, current_level, map->addr); } -- 2.34.1