linux-kernel - Re: [PATCH v2 06/12] RISC-V: KVM: Implement kvm_arch_flush_remote_tlbs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAK9=C2UQAKk3kVswTzKRG43Ds3T3etfK-45Y+Uv2g3wn+Qg1fg@mail.gmail.com>
Date: Tue, 17 Jun 2025 10:28:45 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Atish Patra <atish.patra@...ux.dev>
Cc: Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Alexandre Ghiti <alex@...ti.fr>, Andrew Jones <ajones@...tanamicro.com>, 
	Anup Patel <anup@...infault.org>, kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/12] RISC-V: KVM: Implement kvm_arch_flush_remote_tlbs_range()

On Sat, Jun 14, 2025 at 6:14 AM Atish Patra <atish.patra@...ux.dev> wrote:
>
>
> On 6/12/25 11:57 PM, Anup Patel wrote:
> > The kvm_arch_flush_remote_tlbs_range() expected by KVM core can be
> > easily implemented for RISC-V using kvm_riscv_hfence_gvma_vmid_gpa()
> > hence provide it.
> >
> > Also with kvm_arch_flush_remote_tlbs_range() available for RISC-V, the
> > mmu_wp_memory_region() can happily use kvm_flush_remote_tlbs_memslot()
> > instead of kvm_flush_remote_tlbs().
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > ---
> >   arch/riscv/include/asm/kvm_host.h | 2 ++
> >   arch/riscv/kvm/mmu.c              | 2 +-
> >   arch/riscv/kvm/tlb.c              | 8 ++++++++
> >   3 files changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> > index ff1f76d6f177..6162575e2177 100644
> > --- a/arch/riscv/include/asm/kvm_host.h
> > +++ b/arch/riscv/include/asm/kvm_host.h
> > @@ -43,6 +43,8 @@
> >       KVM_ARCH_REQ_FLAGS(5, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
> >   #define KVM_REQ_STEAL_UPDATE                KVM_ARCH_REQ(6)
> >
> > +#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> > +
> >   #define KVM_HEDELEG_DEFAULT         (BIT(EXC_INST_MISALIGNED) | \
> >                                        BIT(EXC_BREAKPOINT)      | \
> >                                        BIT(EXC_SYSCALL)         | \
> > diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> > index 29f1bd853a66..a5387927a1c1 100644
> > --- a/arch/riscv/kvm/mmu.c
> > +++ b/arch/riscv/kvm/mmu.c
> > @@ -344,7 +344,7 @@ static void gstage_wp_memory_region(struct kvm *kvm, int slot)
> >       spin_lock(&kvm->mmu_lock);
> >       gstage_wp_range(kvm, start, end);
> >       spin_unlock(&kvm->mmu_lock);
> > -     kvm_flush_remote_tlbs(kvm);
> > +     kvm_flush_remote_tlbs_memslot(kvm, memslot);
> >   }
> >
> >   int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
> > diff --git a/arch/riscv/kvm/tlb.c b/arch/riscv/kvm/tlb.c
> > index da98ca801d31..f46a27658c2e 100644
> > --- a/arch/riscv/kvm/tlb.c
> > +++ b/arch/riscv/kvm/tlb.c
> > @@ -403,3 +403,11 @@ void kvm_riscv_hfence_vvma_all(struct kvm *kvm,
> >       make_xfence_request(kvm, hbase, hmask, KVM_REQ_HFENCE_VVMA_ALL,
> >                           KVM_REQ_HFENCE_VVMA_ALL, NULL);
> >   }
> > +
> > +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages)
> > +{
> > +     kvm_riscv_hfence_gvma_vmid_gpa(kvm, -1UL, 0,
> > +                                    gfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT,
> > +                                    PAGE_SHIFT);
> > +     return 0;
> > +}
>
> LGTM. However, I noticed that kvm_flush_remote_tlbs_range doesn't
> increment remote_tlb_flush_requests/remote_tlb_flush stat counter.
>
> So we would be losing those stats here. Do you know if there is a
> specific reason behind not supporting the stat counters in the *tlbs_range
> function ?

Looks like this was missed out in generic kvm_flush_remote_tlbs_range().

Regards,
Anup