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Message-ID: <266701ad-90df-e4c8-bbf7-c6411b759c5f@gmail.com>
Date: Thu, 6 Jul 2023 14:15:13 +1000
From: Jordan Niethe <jniethe5@...il.com>
To: Kautuk Consul <kconsul@...ux.vnet.ibm.com>,
Nicholas Piggin <npiggin@...il.com>,
Fabiano Rosas <farosas@...ux.ibm.com>, jpn@...ux.vnet.ibm.com,
Michael Ellerman <mpe@...erman.id.au>,
Paul Mackerras <paulus@...abs.org>,
Thomas Huth <thuth@...hat.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] KVM: ppc64: Enable ring-based dirty memory tracking
On 8/6/23 10:34 pm, Kautuk Consul wrote:
Need at least a little context in the commit message itself:
"Enable ring-based dirty memory tracking on ppc64:"
> - Enable CONFIG_HAVE_KVM_DIRTY_RING_ACQ_REL as ppc64 is weakly
> ordered.
> - Enable CONFIG_NEED_KVM_DIRTY_RING_WITH_BITMAP because the
> kvmppc_xive_native_set_attr is called in the context of an ioctl
> syscall and will call kvmppc_xive_native_eq_sync for setting the
> KVM_DEV_XIVE_EQ_SYNC attribute which will call mark_dirty_page()
> when there isn't a running vcpu. Implemented the
> kvm_arch_allow_write_without_running_vcpu to always return true
> to allow mark_page_dirty_in_slot to mark the page dirty in the
> memslot->dirty_bitmap in this case.
Should kvm_arch_allow_write_without_running_vcpu() only return true in
the context of kvmppc_xive_native_eq_sync()?
> - Set KVM_DIRTY_LOG_PAGE_OFFSET for the ring buffer's physical page
> offset.
> - Implement the kvm_arch_mmu_enable_log_dirty_pt_masked function required
> for the generic KVM code to call.
> - Add a check to kvmppc_vcpu_run_hv for checking whether the dirty
> ring is soft full.
> - Implement the kvm_arch_flush_remote_tlbs_memslot function to support
> the CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT config option.
>
> On testing with live migration it was found that there is around
> 150-180 ms improvment in overall migration time with this
>
> Signed-off-by: Kautuk Consul <kconsul@...ux.vnet.ibm.com>
> ---
> Documentation/virt/kvm/api.rst | 2 +-
> arch/powerpc/include/uapi/asm/kvm.h | 2 ++
> arch/powerpc/kvm/Kconfig | 2 ++
> arch/powerpc/kvm/book3s_64_mmu_hv.c | 42 +++++++++++++++++++++++++++++
> arch/powerpc/kvm/book3s_hv.c | 3 +++
> include/linux/kvm_dirty_ring.h | 5 ++++
> 6 files changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index add067793b90..ce1ebc513bae 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -8114,7 +8114,7 @@ regardless of what has actually been exposed through the CPUID leaf.
> 8.29 KVM_CAP_DIRTY_LOG_RING/KVM_CAP_DIRTY_LOG_RING_ACQ_REL
> ----------------------------------------------------------
>
> -:Architectures: x86, arm64
> +:Architectures: x86, arm64, ppc64
> :Parameters: args[0] - size of the dirty log ring
>
> KVM is capable of tracking dirty memory using ring buffers that are
> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> index 9f18fa090f1f..f722309ed7fb 100644
> --- a/arch/powerpc/include/uapi/asm/kvm.h
> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> @@ -33,6 +33,8 @@
> /* Not always available, but if it is, this is the correct offset. */
> #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
>
> +#define KVM_DIRTY_LOG_PAGE_OFFSET 64
> +
> struct kvm_regs {
> __u64 pc;
> __u64 cr;
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 902611954200..c93354ec3bd5 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -26,6 +26,8 @@ config KVM
> select IRQ_BYPASS_MANAGER
> select HAVE_KVM_IRQ_BYPASS
> select INTERVAL_TREE
> + select HAVE_KVM_DIRTY_RING_ACQ_REL
> + select NEED_KVM_DIRTY_RING_WITH_BITMAP
>
> config KVM_BOOK3S_HANDLER
> bool
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 7f765d5ad436..c92e8022e017 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -2147,3 +2147,45 @@ void kvmppc_mmu_book3s_hv_init(struct kvm_vcpu *vcpu)
>
> vcpu->arch.hflags |= BOOK3S_HFLAG_SLB;
> }
> +
> +/*
> + * kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
> + * dirty pages.
> + *
> + * It write protects selected pages to enable dirty logging for them.
> + */
> +void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
> + struct kvm_memory_slot *slot,
> + gfn_t gfn_offset,
> + unsigned long mask)
> +{
> + phys_addr_t base_gfn = slot->base_gfn + gfn_offset;
> + phys_addr_t start = (base_gfn + __ffs(mask)) << PAGE_SHIFT;
> + phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
> +
> + while (start < end) {
> + pte_t *ptep;
> + unsigned int shift;
> +
> + ptep = find_kvm_secondary_pte(kvm, start, &shift);
> +
> + *ptep = __pte(pte_val(*ptep) & ~(_PAGE_WRITE));
On rpt I think you'd need to use kvmppc_radix_update_pte()?
> +
> + start += PAGE_SIZE > + }
> +}
> +
> +#ifdef CONFIG_NEED_KVM_DIRTY_RING_WITH_BITMAP
> +bool kvm_arch_allow_write_without_running_vcpu(struct kvm *kvm)
> +{
> + return true;
> +}
> +#endif
> +
> +#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> +void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
> + const struct kvm_memory_slot *memslot)
> +{
> + kvm_flush_remote_tlbs(kvm);
> +}
> +#endif
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 130bafdb1430..1d1264ea72c4 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4804,6 +4804,9 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu)
> return -EINTR;
> }
>
> + if (kvm_dirty_ring_check_request(vcpu))
> + return 0;
> +
> #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> /*
> * Don't allow entry with a suspended transaction, because
> diff --git a/include/linux/kvm_dirty_ring.h b/include/linux/kvm_dirty_ring.h
> index 4862c98d80d3..a00301059da5 100644
> --- a/include/linux/kvm_dirty_ring.h
> +++ b/include/linux/kvm_dirty_ring.h
> @@ -69,6 +69,11 @@ static inline void kvm_dirty_ring_free(struct kvm_dirty_ring *ring)
> {
> }
>
> +static inline bool kvm_dirty_ring_check_request(struct kvm_vcpu *vcpu)
> +{
> + return false;
> +}
> + > #else /* CONFIG_HAVE_KVM_DIRTY_RING */
>
> int kvm_cpu_dirty_log_size(void);
>
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