Commit 2ffd9e33 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Ingo Molnar
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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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: default avatarStephen Hemminger <sthemmin@microsoft.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jork Loeser <Jork.Loeser@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Simon Xiao <sixiao@microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: devel@linuxdriverproject.org
Link: http://lkml.kernel.org/r/20170802160921.21791-8-vkuznets@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7415aea6
obj-y := hv_init.o
obj-y := hv_init.o mmu.o
......@@ -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.
*/
......
#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);
}
......@@ -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
......
......@@ -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
......
......@@ -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
}
......
......@@ -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.
......
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