Commit fdec9918 authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Alexander Graf

s390: autodetect map private

By default qemu will use MAP_PRIVATE for guest pages. This will write
protect pages and thus break on s390 systems that dont support this feature.
Therefore qemu has a hack to always use MAP_SHARED for s390. But MAP_SHARED
has other problems (no dirty pages tracking, a lot more swap overhead etc.)
Newer systems allow the distinction via KVM_CAP_S390_COW. With this feature
qemu can use the standard qemu alloc if available, otherwise it will use
the old s390 hack.
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarJens Freimann <jfrei@linux.vnet.ibm.com>
Acked-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
parent 92336855
......@@ -2536,26 +2536,14 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
exit(1);
#endif
} else {
#if defined(TARGET_S390X) && defined(CONFIG_KVM)
/* S390 KVM requires the topmost vma of the RAM to be smaller than
an system defined value, which is at least 256GB. Larger systems
have larger values. We put the guest between the end of data
segment (system break) and this value. We use 32GB as a base to
have enough room for the system break to grow. */
new_block->host = mmap((void*)0x800000000, size,
PROT_EXEC|PROT_READ|PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if (new_block->host == MAP_FAILED) {
fprintf(stderr, "Allocating RAM failed\n");
abort();
}
#else
if (xen_enabled()) {
xen_ram_alloc(new_block->offset, size, mr);
} else if (kvm_enabled()) {
/* some s390/kvm configurations have special constraints */
new_block->host = kvm_vmalloc(size);
} else {
new_block->host = qemu_vmalloc(size);
}
#endif
qemu_madvise(new_block->host, size, QEMU_MADV_MERGEABLE);
}
}
......
......@@ -1655,6 +1655,19 @@ int kvm_allows_irq0_override(void)
return !kvm_irqchip_in_kernel() || kvm_has_gsi_routing();
}
void *kvm_vmalloc(ram_addr_t size)
{
#ifdef TARGET_S390X
void *mem;
mem = kvm_arch_vmalloc(size);
if (mem) {
return mem;
}
#endif
return qemu_vmalloc(size);
}
void kvm_setup_guest_memory(void *start, size_t size)
{
if (!kvm_has_sync_mmu()) {
......
......@@ -70,6 +70,8 @@ int kvm_init_vcpu(CPUArchState *env);
int kvm_cpu_exec(CPUArchState *env);
#if !defined(CONFIG_USER_ONLY)
void *kvm_vmalloc(ram_addr_t size);
void *kvm_arch_vmalloc(ram_addr_t size);
void kvm_setup_guest_memory(void *start, size_t size);
int kvm_coalesce_mmio_region(target_phys_addr_t start, ram_addr_t size);
......
......@@ -41,6 +41,9 @@ extern int daemon(int, int);
therefore we need special code which handles running on Valgrind. */
# define QEMU_VMALLOC_ALIGN (512 * 4096)
# define CONFIG_VALGRIND
#elif defined(__linux__) && defined(__s390x__)
/* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
# define QEMU_VMALLOC_ALIGN (256 * 4096)
#else
# define QEMU_VMALLOC_ALIGN getpagesize()
#endif
......
......@@ -135,6 +135,41 @@ int kvm_arch_get_registers(CPUS390XState *env)
return 0;
}
/*
* Legacy layout for s390:
* Older S390 KVM requires the topmost vma of the RAM to be
* smaller than an system defined value, which is at least 256GB.
* Larger systems have larger values. We put the guest between
* the end of data segment (system break) and this value. We
* use 32GB as a base to have enough room for the system break
* to grow. We also have to use MAP parameters that avoid
* read-only mapping of guest pages.
*/
static void *legacy_s390_alloc(ram_addr_t size)
{
void *mem;
mem = mmap((void *) 0x800000000ULL, size,
PROT_EXEC|PROT_READ|PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
if (mem == MAP_FAILED) {
fprintf(stderr, "Allocating RAM failed\n");
abort();
}
return mem;
}
void *kvm_arch_vmalloc(ram_addr_t size)
{
/* Can we use the standard allocation ? */
if (kvm_check_extension(kvm_state, KVM_CAP_S390_GMAP) &&
kvm_check_extension(kvm_state, KVM_CAP_S390_COW)) {
return NULL;
} else {
return legacy_s390_alloc(size);
}
}
int kvm_arch_insert_sw_breakpoint(CPUS390XState *env, struct kvm_sw_breakpoint *bp)
{
static const uint8_t diag_501[] = {0x83, 0x24, 0x05, 0x01};
......
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