[PATCH v14 01/25] x86/kvmclock: Remove memblock dependency

Pavel Tatashin
2018-07-18T02:21:47Z

KVM clock is initialized later compared to other hypervisor clocks because
it has a dependency on the memblock allocator.

Bring it in line with other hypervisors by using memory from the BSS
instead of allocating it.

The benefits:

- Remove ifdef from common code
- Earlier availability of the clock
- Remove dependency on memblock, and reduce code

The downside:

- Static allocation of the per cpu data structures sized NR_CPUS * 64byte
Will be addressed in follow up patches.

[ tglx: Split out from larger series ]

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kernel/kvm.c | 1 +
arch/x86/kernel/kvmclock.c | 66 +++++++-------------------------------
arch/x86/kernel/setup.c | 4 ---
3 files changed, 12 insertions(+), 59 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 5b2300b818af..c65c232d3ddd 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -628,6 +628,7 @@ const __initconst struct hypervisor_x86 x86_hyper_kvm = {
.name = "KVM",
.detect = kvm_detect,
.type = X86_HYPER_KVM,
+ .init.init_platform = kvmclock_init,
.init.guest_late_init = kvm_guest_init,
.init.x2apic_available = kvm_para_available,
};
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index bf8d1eb7fca3..890e9e58e4bf 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -23,9 +23,9 @@
#include <asm/apic.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
-#include <linux/memblock.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
+#include <linux/mm.h>

#include <asm/mem_encrypt.h>
#include <asm/x86_init.h>
@@ -44,6 +44,13 @@ static int parse_no_kvmclock(char *arg)
}
early_param("no-kvmclock", parse_no_kvmclock);

+/* Aligned to page sizes to match whats mapped via vsyscalls to userspace */
+#define HV_CLOCK_SIZE (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS)
+#define WALL_CLOCK_SIZE (sizeof(struct pvclock_wall_clock))
+
+static u8 hv_clock_mem[PAGE_ALIGN(HV_CLOCK_SIZE)] __aligned(PAGE_SIZE);
+static u8 wall_clock_mem[PAGE_ALIGN(WALL_CLOCK_SIZE)] __aligned(PAGE_SIZE);
+
/* The hypervisor will put information about time periodically here */
static struct pvclock_vsyscall_time_info *hv_clock;
static struct pvclock_wall_clock *wall_clock;
@@ -244,43 +251,12 @@ static void kvm_shutdown(void)
native_machine_shutdown();
}

-static phys_addr_t __init kvm_memblock_alloc(phys_addr_t size,
- phys_addr_t align)
-{
- phys_addr_t mem;
-
- mem = memblock_alloc(size, align);
- if (!mem)
- return 0;
-
- if (sev_active()) {
- if (early_set_memory_decrypted((unsigned long)__va(mem), size))
- goto e_free;
- }
-
- return mem;
-e_free:
- memblock_free(mem, size);
- return 0;
-}
-
-static void __init kvm_memblock_free(phys_addr_t addr, phys_addr_t size)
-{
- if (sev_active())
- early_set_memory_encrypted((unsigned long)__va(addr), size);
-
- memblock_free(addr, size);
-}
-
void __init kvmclock_init(void)
{
struct pvclock_vcpu_time_info *vcpu_time;
- unsigned long mem, mem_wall_clock;
- int size, cpu, wall_clock_size;
+ int cpu;
u8 flags;

- size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
-
if (!kvm_para_available())
return;

@@ -290,28 +266,11 @@ void __init kvmclock_init(void)
} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
return;

- wall_clock_size = PAGE_ALIGN(sizeof(struct pvclock_wall_clock));
- mem_wall_clock = kvm_memblock_alloc(wall_clock_size, PAGE_SIZE);
- if (!mem_wall_clock)
- return;
-
- wall_clock = __va(mem_wall_clock);
- memset(wall_clock, 0, wall_clock_size);
-
- mem = kvm_memblock_alloc(size, PAGE_SIZE);
- if (!mem) {
- kvm_memblock_free(mem_wall_clock, wall_clock_size);
- wall_clock = NULL;
- return;
- }
-
- hv_clock = __va(mem);
- memset(hv_clock, 0, size);
+ wall_clock = (struct pvclock_wall_clock *)wall_clock_mem;
+ hv_clock = (struct pvclock_vsyscall_time_info *)hv_clock_mem;

if (kvm_register_clock("primary cpu clock")) {
hv_clock = NULL;
- kvm_memblock_free(mem, size);
- kvm_memblock_free(mem_wall_clock, wall_clock_size);
wall_clock = NULL;
return;
}
@@ -354,13 +313,10 @@ int __init kvm_setup_vsyscall_timeinfo(void)
int cpu;
u8 flags;
struct pvclock_vcpu_time_info *vcpu_time;
- unsigned int size;

if (!hv_clock)
return 0;

- size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
-
cpu = get_cpu();

vcpu_time = &hv_clock[cpu].pvti;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 2f86d883dd95..da1dbd99cb6e 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1197,10 +1197,6 @@ void __init setup_arch(char **cmdline_p)

memblock_find_dma_reserve();

-#ifdef CONFIG_KVM_GUEST
- kvmclock_init();
-#endif
-
tsc_early_delay_calibrate();
if (!early_xdbc_setup_hardware())
early_xdbc_register_console();
--
2.18.0