Re: [RFC] KVM: arm64: support enabling dirty log graually in small chunks
From: Marc Zyngier
Date: Mon Mar 09 2020 - 07:45:43 EST
Kegian,
In the future, please Cc me on your KVM/arm64 patches, as well as
all the reviewers mentioned in the MAINTAINERS file.
On 2020-03-09 08:57, Keqian Zhu wrote:
There is already support of enabling dirty log graually
gradually?
in small chunks for x86. This adds support for arm64.
Under the Huawei Kunpeng 920 2.6GHz platform, I did some
tests with a 128G linux VM and counted the time taken of
Linux
memory_global_dirty_log_start, here is the numbers:
VM Size Before After optimization
128G 527ms 4ms
What does this benchmark do? Can you please provide a pointer to it?
Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
---
Cc: Jay Zhou <jianjay.zhou@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 2 +-
arch/arm64/include/asm/kvm_host.h | 4 ++++
virt/kvm/arm/mmu.c | 30 ++++++++++++++++++++++--------
3 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst
b/Documentation/virt/kvm/api.rst
index 0adef66585b1..89d4f2680af1 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5735,7 +5735,7 @@ will be initialized to 1 when created. This
also improves performance because
dirty logging can be enabled gradually in small chunks on the first
call
to KVM_CLEAR_DIRTY_LOG. KVM_DIRTY_LOG_INITIALLY_SET depends on
KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (it is also only available on
-x86 for now).
+x86 and arm64 for now).
What is this based on? I can't find this in -next, and you provide no
context whatsoever.
I assume this is related to this:
https://lore.kernel.org/kvm/20200227013227.1401-1-jianjay.zhou@xxxxxxxxxx/
Is there a userspace counterpart to it?
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the
name
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that
make
diff --git a/arch/arm64/include/asm/kvm_host.h
b/arch/arm64/include/asm/kvm_host.h
index d87aa609d2b6..0deb2ac7d091 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -16,6 +16,7 @@
#include <linux/jump_label.h>
#include <linux/kvm_types.h>
#include <linux/percpu.h>
+#include <linux/kvm.h>
#include <asm/arch_gicv3.h>
#include <asm/barrier.h>
#include <asm/cpufeature.h>
@@ -45,6 +46,9 @@
#define KVM_REQ_VCPU_RESET KVM_ARCH_REQ(2)
#define KVM_REQ_RECORD_STEAL KVM_ARCH_REQ(3)
+#define KVM_DIRTY_LOG_MANUAL_CAPS
(KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE | \
+ KVM_DIRTY_LOG_INITIALLY_SET)
+
DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
extern unsigned int kvm_sve_max_vl;
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index e3b9ee268823..5c7ca84dec85 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1438,9 +1438,11 @@ static void stage2_wp_ptes(pmd_t *pmd,
phys_addr_t addr, phys_addr_t end)
* @pud: pointer to pud entry
* @addr: range start address
* @end: range end address
+ * @wp_ptes: write protect ptes or not
*/
static void stage2_wp_pmds(struct kvm *kvm, pud_t *pud,
- phys_addr_t addr, phys_addr_t end)
+ phys_addr_t addr, phys_addr_t end,
+ bool wp_ptes)
If you are going to pass extra parameters like this, make it at least
extensible (unsigned long flags, for example).
{
pmd_t *pmd;
phys_addr_t next;
@@ -1453,7 +1455,7 @@ static void stage2_wp_pmds(struct kvm *kvm, pud_t
*pud,
if (pmd_thp_or_huge(*pmd)) {
if (!kvm_s2pmd_readonly(pmd))
kvm_set_s2pmd_readonly(pmd);
- } else {
+ } else if (wp_ptes) {
stage2_wp_ptes(pmd, addr, next);
}
}
@@ -1465,9 +1467,11 @@ static void stage2_wp_pmds(struct kvm *kvm,
pud_t *pud,
* @pgd: pointer to pgd entry
* @addr: range start address
* @end: range end address
+ * @wp_ptes: write protect ptes or not
*/
static void stage2_wp_puds(struct kvm *kvm, pgd_t *pgd,
- phys_addr_t addr, phys_addr_t end)
+ phys_addr_t addr, phys_addr_t end,
+ bool wp_ptes)
{
pud_t *pud;
phys_addr_t next;
@@ -1480,7 +1484,7 @@ static void stage2_wp_puds(struct kvm *kvm,
pgd_t *pgd,
if (!kvm_s2pud_readonly(pud))
kvm_set_s2pud_readonly(pud);
} else {
- stage2_wp_pmds(kvm, pud, addr, next);
+ stage2_wp_pmds(kvm, pud, addr, next, wp_ptes);
}
}
} while (pud++, addr = next, addr != end);
@@ -1491,8 +1495,10 @@ static void stage2_wp_puds(struct kvm *kvm,
pgd_t *pgd,
* @kvm: The KVM pointer
* @addr: Start address of range
* @end: End address of range
+ * @wp_ptes: Write protect ptes or not
*/
-static void stage2_wp_range(struct kvm *kvm, phys_addr_t addr,
phys_addr_t end)
+static void stage2_wp_range(struct kvm *kvm, phys_addr_t addr,
+ phys_addr_t end, bool wp_ptes)
{
pgd_t *pgd;
phys_addr_t next;
@@ -1513,7 +1519,7 @@ static void stage2_wp_range(struct kvm *kvm,
phys_addr_t addr, phys_addr_t end)
break;
next = stage2_pgd_addr_end(kvm, addr, end);
if (stage2_pgd_present(kvm, *pgd))
- stage2_wp_puds(kvm, pgd, addr, next);
+ stage2_wp_puds(kvm, pgd, addr, next, wp_ptes);
} while (pgd++, addr = next, addr != end);
}
@@ -1535,6 +1541,7 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm,
int slot)
struct kvm_memslots *slots = kvm_memslots(kvm);
struct kvm_memory_slot *memslot = id_to_memslot(slots, slot);
phys_addr_t start, end;
+ bool wp_ptes;
if (WARN_ON_ONCE(!memslot))
return;
@@ -1543,7 +1550,14 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm,
int slot)
end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;
spin_lock(&kvm->mmu_lock);
- stage2_wp_range(kvm, start, end);
+ /*
+ * If we're with initial-all-set, we don't need to write protect
+ * any small page because they're reported as dirty already.
+ * However we still need to write-protect huge pages so that the
+ * page split can happen lazily on the first write to the huge page.
+ */
+ wp_ptes = !kvm_dirty_log_manual_protect_and_init_set(kvm);
+ stage2_wp_range(kvm, start, end, wp_ptes);
spin_unlock(&kvm->mmu_lock);
kvm_flush_remote_tlbs(kvm);
}
@@ -1567,7 +1581,7 @@ static void
kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
phys_addr_t start = (base_gfn + __ffs(mask)) << PAGE_SHIFT;
phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
- stage2_wp_range(kvm, start, end);
+ stage2_wp_range(kvm, start, end, true);
}
/*
Thanks,
M.
--
Jazz is not dead. It just smells funny...