From: Atish Patra <atish.patra@linux.dev>
To: Anup Patel <apatel@ventanamicro.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Alexandre Ghiti <alex@ghiti.fr>,
Andrew Jones <ajones@ventanamicro.com>,
Anup Patel <anup@brainfault.org>,
kvm@vger.kernel.org, kvm-riscv@lists.infradead.org,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 05/12] RISC-V: KVM: Don't flush TLB when PTE is unchanged
Date: Fri, 13 Jun 2025 17:09:41 -0700 [thread overview]
Message-ID: <ffd04c9b-030d-4eaa-bbf6-d1f416565c35@linux.dev> (raw)
In-Reply-To: <20250613065743.737102-6-apatel@ventanamicro.com>
On 6/12/25 11:57 PM, Anup Patel wrote:
> 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>
> ---
> 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 = &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);
> }
> }
>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
next prev parent reply other threads:[~2025-06-14 0:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-13 6:57 [PATCH v2 00/12] MMU related improvements for KVM RISC-V Anup Patel
2025-06-13 6:57 ` [PATCH v2 01/12] RISC-V: KVM: Check kvm_riscv_vcpu_alloc_vector_context() return value Anup Patel
2025-06-13 6:57 ` [PATCH v2 02/12] RISC-V: KVM: Drop the return value of kvm_riscv_vcpu_aia_init() Anup Patel
2025-06-13 6:57 ` [PATCH v2 03/12] RISC-V: KVM: Rename and move kvm_riscv_local_tlb_sanitize() Anup Patel
2025-06-13 6:57 ` [PATCH v2 04/12] RISC-V: KVM: Replace KVM_REQ_HFENCE_GVMA_VMID_ALL with KVM_REQ_TLB_FLUSH Anup Patel
2025-06-13 6:57 ` [PATCH v2 05/12] RISC-V: KVM: Don't flush TLB when PTE is unchanged Anup Patel
2025-06-14 0:09 ` Atish Patra [this message]
2025-06-13 6:57 ` [PATCH v2 06/12] RISC-V: KVM: Implement kvm_arch_flush_remote_tlbs_range() Anup Patel
2025-06-14 0:43 ` Atish Patra
2025-06-17 4:58 ` Anup Patel
2025-06-13 6:57 ` [PATCH v2 07/12] RISC-V: KVM: Use ncsr_xyz() in kvm_riscv_vcpu_trap_redirect() Anup Patel
2025-06-14 0:46 ` Atish Patra
2025-06-13 6:57 ` [PATCH v2 08/12] RISC-V: KVM: Factor-out MMU related declarations into separate headers Anup Patel
2025-06-18 6:41 ` Atish Patra
2025-06-13 6:57 ` [PATCH v2 09/12] RISC-V: KVM: Introduce struct kvm_gstage_mapping Anup Patel
2025-06-18 7:36 ` Atish Patra
2025-06-13 6:57 ` [PATCH v2 10/12] RISC-V: KVM: Add vmid field to struct kvm_riscv_hfence Anup Patel
2025-06-14 19:29 ` Atish Patra
2025-06-13 6:57 ` [PATCH v2 11/12] RISC-V: KVM: Factor-out g-stage page table management Anup Patel
2025-06-13 6:57 ` [PATCH v2 12/12] RISC-V: KVM: Pass VMID as parameter to kvm_riscv_hfence_xyz() APIs Anup Patel
2025-06-14 19:12 ` Atish Patra
2025-06-14 19:18 ` Atish Patra
2025-06-17 5:11 ` Anup Patel
2025-06-18 6:40 ` Atish Patra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ffd04c9b-030d-4eaa-bbf6-d1f416565c35@linux.dev \
--to=atish.patra@linux.dev \
--cc=ajones@ventanamicro.com \
--cc=alex@ghiti.fr \
--cc=anup@brainfault.org \
--cc=apatel@ventanamicro.com \
--cc=kvm-riscv@lists.infradead.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=palmer@dabbelt.com \
--cc=paul.walmsley@sifive.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®