From: Dylan.Wu <fredwudi0305@gmail.com>
Date: Wed, 1 Jul 2026 07:52:39 +0000 (-0400)
Subject: riscv: kvm: Skip TLB flush when G-stage PTE becomes valid with Svvptc
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1cc935ec2d87673e3c52ba04f943ab1276c0635b;p=thirdparty%2Fkernel%2Flinux.git

riscv: kvm: Skip TLB flush when G-stage PTE becomes valid with Svvptc

The gstage_tlb_flush() in the kvm_riscv_gstage_set_pte() is not needed
when an invalid G-stage PTE becomes valid and Svvptc extension is available
because new valid PTEs become visible to the page-table walker within a
bounded time.

Assisted-by: YuanSheng: deepseek-v4-pro
Co-developed-by: Quan Zhou <zhouquan@iscas.ac.cn>
Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
Signed-off-by: Dylan.Wu <fredwudi0305@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260701075239.95542-1-fredwudi0305@gmail.com
Signed-off-by: Anup Patel <anup@brainfault.org>
---

diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index c4c3b79567f1..b0474fcf065a 100644
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -5,11 +5,13 @@
  */
 
 #include <linux/bitops.h>
+#include <linux/cpufeature.h>
 #include <linux/errno.h>
 #include <linux/kvm_host.h>
 #include <linux/module.h>
 #include <linux/pgtable.h>
 #include <asm/kvm_gstage.h>
+#include <asm/hwcap.h>
 
 #ifdef CONFIG_64BIT
 unsigned long kvm_riscv_gstage_max_pgd_levels __ro_after_init = 3;
@@ -171,8 +173,10 @@ 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);
 	}