[tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush
From: tip-bot for Vitaly Kuznetsov
Date: Thu Aug 10 2017 - 14:26:44 EST
Commit-ID: 2ffd9e33ce4af4e8cfa3e17bf493defe8474e2eb
Gitweb: http://git.kernel.org/tip/2ffd9e33ce4af4e8cfa3e17bf493defe8474e2eb
Author: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
AuthorDate: Wed, 2 Aug 2017 18:09:19 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 10 Aug 2017 20:16:44 +0200
x86/hyper-v: Use hypercall for remote TLB flush
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.
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>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Reviewed-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Jork Loeser <Jork.Loeser@xxxxxxxxxxxxx>
Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Simon Xiao <sixiao@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: devel@xxxxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170802160921.21791-8-vkuznets@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/hyperv/Makefile | 2 +-
arch/x86/hyperv/hv_init.c | 2 +
arch/x86/hyperv/mmu.c | 138 +++++++++++++++++++++++++++++++++++++
arch/x86/include/asm/mshyperv.h | 3 +
arch/x86/include/uapi/asm/hyperv.h | 7 ++
arch/x86/kernel/cpu/mshyperv.c | 1 +
drivers/hv/Kconfig | 1 +
7 files changed, 153 insertions(+), 1 deletion(-)
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 e93b9a0..1a8eb55 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -140,6 +140,8 @@ 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..9419a20
--- /dev/null
+++ b/arch/x86/hyperv/mmu.c
@@ -0,0 +1,138 @@
+#define pr_fmt(fmt) "Hyper-V: " fmt
+
+#include <linux/hyperv.h>
+#include <linux/log2.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/fpu/api.h>
+#include <asm/mshyperv.h>
+#include <asm/msr.h>
+#include <asm/tlbflush.h>
+
+/* HvFlushVirtualAddressSpace, HvFlushVirtualAddressList hypercalls */
+struct hv_flush_pcpu {
+ u64 address_space;
+ u64 flags;
+ u64 processor_mask;
+ u64 gva_list[];
+};
+
+/* Each gva in gva_list encodes up to 4096 pages to flush */
+#define HV_TLB_FLUSH_UNIT (4096 * PAGE_SIZE)
+
+static struct hv_flush_pcpu __percpu *pcpu_flush;
+
+/*
+ * Fills in gva_list starting from offset. Returns the number of items added.
+ */
+static inline int fill_gva_list(u64 gva_list[], int offset,
+ unsigned long start, unsigned long end)
+{
+ int gva_n = offset;
+ unsigned long cur = start, diff;
+
+ do {
+ diff = end > cur ? end - cur : 0;
+
+ 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 (diff >= HV_TLB_FLUSH_UNIT)
+ gva_list[gva_n] |= ~PAGE_MASK;
+ else if (diff)
+ gva_list[gva_n] |= (diff - 1) >> PAGE_SHIFT;
+
+ cur += HV_TLB_FLUSH_UNIT;
+ gva_n++;
+
+ } while (cur < end);
+
+ return gva_n - offset;
+}
+
+static void hyperv_flush_tlb_others(const struct cpumask *cpus,
+ const struct flush_tlb_info *info)
+{
+ int cpu, vcpu, gva_n, max_gvas;
+ struct hv_flush_pcpu *flush;
+ u64 status = U64_MAX;
+ unsigned long flags;
+
+ if (!pcpu_flush || !hv_hypercall_pg)
+ goto do_native;
+
+ if (cpumask_empty(cpus))
+ return;
+
+ local_irq_save(flags);
+
+ flush = this_cpu_ptr(pcpu_flush);
+
+ if (info->mm) {
+ flush->address_space = virt_to_phys(info->mm->pgd);
+ flush->flags = 0;
+ } else {
+ flush->address_space = 0;
+ flush->flags = HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES;
+ }
+
+ flush->processor_mask = 0;
+ if (cpumask_equal(cpus, cpu_present_mask)) {
+ flush->flags |= HV_FLUSH_ALL_PROCESSORS;
+ } else {
+ for_each_cpu(cpu, cpus) {
+ vcpu = hv_cpu_number_to_vp_number(cpu);
+ if (vcpu >= 64)
+ goto do_native;
+
+ __set_bit(vcpu, (unsigned long *)
+ &flush->processor_mask);
+ }
+ }
+
+ /*
+ * We can flush not more than max_gvas with one hypercall. Flush the
+ * whole address space if we were asked to do more.
+ */
+ max_gvas = (PAGE_SIZE - sizeof(*flush)) / sizeof(flush->gva_list[0]);
+
+ if (info->end == TLB_FLUSH_ALL) {
+ flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY;
+ status = hv_do_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE,
+ flush, NULL);
+ } else if (info->end &&
+ ((info->end - info->start)/HV_TLB_FLUSH_UNIT) > max_gvas) {
+ status = hv_do_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE,
+ flush, NULL);
+ } else {
+ gva_n = fill_gva_list(flush->gva_list, 0,
+ info->start, info->end);
+ status = hv_do_rep_hypercall(HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST,
+ gva_n, 0, flush, NULL);
+ }
+
+ local_irq_restore(flags);
+
+ if (!(status & HV_HYPERCALL_RESULT_MASK))
+ return;
+do_native:
+ native_flush_tlb_others(cpus, info);
+}
+
+void hyperv_setup_mmu_ops(void)
+{
+ if (ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED) {
+ pr_info("Using hypercall for remote TLB flush\n");
+ pv_mmu_ops.flush_tlb_others = hyperv_flush_tlb_others;
+ setup_clear_cpu_cap(X86_FEATURE_PCID);
+ }
+}
+
+void hyper_alloc_mmu(void)
+{
+ if (ms_hyperv.hints & HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED)
+ pcpu_flush = __alloc_percpu(PAGE_SIZE, PAGE_SIZE);
+}
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index efd2f80..0d4b01c 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -307,6 +307,8 @@ static inline int hv_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);
@@ -314,6 +316,7 @@ void hyperv_cleanup(void);
static inline void hyperv_init(void) {}
static inline bool hv_is_hypercall_page_setup(void) { return false; }
static inline void hyperv_cleanup(void) {}
+static inline void hyperv_setup_mmu_ops(void) {}
#endif /* CONFIG_HYPERV */
#ifdef CONFIG_HYPERV_TSCPAGE
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 127ddad..a6fdd3b 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -242,6 +242,8 @@
(~((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
@@ -259,6 +261,11 @@
#define HV_PROCESSOR_POWER_STATE_C2 2
#define HV_PROCESSOR_POWER_STATE_C3 3
+#define HV_FLUSH_ALL_PROCESSORS BIT(0)
+#define HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES BIT(1)
+#define HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY BIT(2)
+#define HV_FLUSH_USE_EXTENDED_RANGE_FORMAT BIT(3)
+
/* hypercall status code */
#define HV_STATUS_SUCCESS 0
#define HV_STATUS_INVALID_HYPERCALL_CODE 2
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 70e717f..daefd67 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -249,6 +249,7 @@ 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
}
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index c29cd53..50b89ea 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -3,6 +3,7 @@ menu "Microsoft Hyper-V guest support"
config HYPERV
tristate "Microsoft Hyper-V client drivers"
depends on X86 && ACPI && PCI && X86_LOCAL_APIC && HYPERVISOR_GUEST
+ select PARAVIRT
help
Select this option to run Linux as a Hyper-V client operating
system.