Hyper-V host can suggest us to use hypercall for doing remote TLB flush,
this is supposed to work faster than IPIs.
Implementation details: to do HvFlushVirtualAddress{Space,List} hypercalls
we need to put the input somewhere in memory and we don't really want to
have memory allocation on each call so we pre-allocate per cpu memory areas
on boot. These areas are of fixes size, limit them with an arbitrary number
of 16 (16 gvas are able to specify 16 * 4096 pages).
pv_ops patching is happening very early so we need to separate
hyperv_setup_mmu_ops() and hyper_alloc_mmu().
It is possible and easy to implement local TLB flushing too and there is
even a hint for that. However, I don't see a room for optimization on the
host side as both hypercall and native tlb flush will result in vmexit. The
hint is also not set on modern Hyper-V versions.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/hyperv/Makefile | 2 +-
arch/x86/hyperv/hv_init.c | 2 +
arch/x86/hyperv/mmu.c | 128 +++++++++++++++++++++++++++++++++++++
arch/x86/include/asm/mshyperv.h | 2 +
arch/x86/include/uapi/asm/hyperv.h | 7 ++
arch/x86/kernel/cpu/mshyperv.c | 1 +
6 files changed, 141 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/hyperv/mmu.c
diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
index 171ae09..367a820 100644
--- a/arch/x86/hyperv/Makefile
+++ b/arch/x86/hyperv/Makefile
@@ -1 +1 @@
-obj-y := hv_init.o
+obj-y := hv_init.o mmu.o
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 1c14088..2cf8a98 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -163,6 +163,8 @@ void hyperv_init(void)
hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+ hyper_alloc_mmu();
+
/*
* Register Hyper-V specific clocksource.
*/
diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
new file mode 100644
index 0000000..fb487cb
--- /dev/null
+++ b/arch/x86/hyperv/mmu.c
@@ -0,0 +1,128 @@
+#include <linux/types.h>
+#include <linux/hyperv.h>
+#include <linux/slab.h>
+#include <asm/mshyperv.h>
+#include <asm/tlbflush.h>
+#include <asm/msr.h>
+#include <asm/fpu/api.h>
+
+/*
+ * Arbitrary number; we need to pre-allocate per-cpu struct for doing TLB
+ * flush hypercalls and we need to pick a size. '16' means we'll be able
+ * to flush 16 * 4096 pages (256MB) with one hypercall.
+ */
+#define HV_MMU_MAX_GVAS 16
+
+/* HvFlushVirtualAddressSpace*, HvFlushVirtualAddressList hypercalls */
+struct hv_flush_pcpu {
+ struct {
+ __u64 address_space;
+ __u64 flags;
+ __u64 processor_mask;
+ __u64 gva_list[HV_MMU_MAX_GVAS];
+ } flush;
+
+ spinlock_t lock;
+};
+
+static struct hv_flush_pcpu __percpu *pcpu_flush;
+
+static void hyperv_flush_tlb_others(const struct cpumask *cpus,
+ struct mm_struct *mm, unsigned long start,
+ unsigned long end)
+{
+ struct hv_flush_pcpu *flush;
+ unsigned long cur, flags;
+ u64 status = -1ULL;
+ int cpu, vcpu, gva_n;
+
+ if (!pcpu_flush || !hv_hypercall_pg)
+ goto do_native;
+
+ if (cpumask_empty(cpus))
+ return;
+
+ flush = this_cpu_ptr(pcpu_flush);
+ spin_lock_irqsave(&flush->lock, flags);
+
+ flush->flush.address_space = virt_to_phys(mm->pgd);
+ flush->flush.processor_mask = 0;
+ if (cpumask_equal(cpus, cpu_present_mask)) {
+ flush->flush.flags = HV_FLUSH_ALL_PROCESSORS;
+ } else {
+ flush->flush.flags = 0;
+ for_each_cpu(cpu, cpus) {
+ vcpu = vmbus_cpu_number_to_vp_number(cpu);
+ if (vcpu != -1 && vcpu < 64)
+ flush->flush.processor_mask |= 1 << vcpu;
+ else
+ goto unlock_do_native;
+ }
+ }
+
+ if (end == TLB_FLUSH_ALL) {
+ flush->flush.flags = HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY;
+ status = hv_do_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE,
+ &flush->flush, NULL);
+ } else {
+ cur = start;
+more_gvas:
+ gva_n = 0;
+
+ do {
+ flush->flush.gva_list[gva_n] = cur & PAGE_MASK;
+ /*
+ * Lower 12 bits encode the number of additional
+ * pages to flush (in addition to the 'cur' page).
+ */
+ if (end >= cur + PAGE_SIZE * PAGE_SIZE)
+ flush->flush.gva_list[gva_n] |= ~PAGE_MASK;
+ else if (end > cur)
+ flush->flush.gva_list[gva_n] |=
+ (end - cur - 1) >> PAGE_SHIFT;
+
+ cur += PAGE_SIZE * PAGE_SIZE;
+ ++gva_n;
+
+ } while (cur < end && gva_n < HV_MMU_MAX_GVAS);
+
+ status = hv_do_rep_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST,
+ gva_n, &flush->flush, NULL);
+
+ if (!(status & 0xffff) && cur < end)
+ goto more_gvas;
+ }
+
+unlock_do_native:
+ spin_unlock_irqrestore(&flush->lock, flags);
+
+ if (!(status & 0xffff))
+ return;
+do_native:
+ native_flush_tlb_others(cpus, mm, start, end);
+}
+
+void hyperv_setup_mmu_ops(void)
+{
+ if (ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED) {
+ pr_info("Hyper-V: Using hypercall for remote TLB flush\n");
+ pv_mmu_ops.flush_tlb_others = hyperv_flush_tlb_others;
+ }
+}
+
+void hyper_alloc_mmu(void)
+{
+ int cpu;
+ struct hv_flush_pcpu *flush;
+
+ if (ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED) {
+ pcpu_flush = alloc_percpu(struct hv_flush_pcpu);
+ if (!pcpu_flush)
+ return;
+
+ for_each_possible_cpu(cpu) {
+ flush = per_cpu_ptr(pcpu_flush, cpu);
+ spin_lock_init(&flush->lock);
+ }
+ }
+}
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 1293c84..a5041c3 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -301,6 +301,8 @@ static inline int vmbus_cpu_number_to_vp_number(int cpu_number)
}
void hyperv_init(void);
+void hyperv_setup_mmu_ops(void);
+void hyper_alloc_mmu(void);
void hyperv_report_panic(struct pt_regs *regs);
bool hv_is_hypercall_page_setup(void);
void hyperv_cleanup(void);
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index c87e900..3d44036 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -239,6 +239,8 @@
(~((1ull << HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT) - 1))
/* Declare the various hypercall operations. */
+#define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE 0x0002
+#define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST 0x0003
#define HVCALL_NOTIFY_LONG_SPIN_WAIT 0x0008
#define HVCALL_POST_MESSAGE 0x005c
#define HVCALL_SIGNAL_EVENT 0x005d
@@ -256,6 +258,11 @@
#define HV_PROCESSOR_POWER_STATE_C2 2
#define HV_PROCESSOR_POWER_STATE_C3 3
+#define HV_FLUSH_ALL_PROCESSORS 0x00000001
+#define HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES 0x00000002
+#define HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY 0x00000004
+#define HV_FLUSH_USE_EXTENDED_RANGE_FORMAT 0x00000008
+
/* Hypercall interface */
union hv_hypercall_input {
u64 as_uint64;
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 04cb8d3..fc228d8 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -233,6 +233,7 @@ static void __init ms_hyperv_init_platform(void)
* Setup the hook to get control post apic initialization.
*/
x86_platform.apic_post_init = hyperv_init;
+ hyperv_setup_mmu_ops();
#endif
}
--
2.9.3
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