| Message ID | 20181129171230.18699-11-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | 80424b02d42bb22f8ff8839cb93a84ade53b39c0 |
| Headers | show |
| Series | EFI updates | expand |
* Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > The current implementation of efi_mem_reserve_persistent() is rather > naive, in the sense that for each invocation, it creates a separate > linked list entry to describe the reservation. Since the linked list > entries themselves need to persist across subsequent kexec reboots, > every reservation created this way results in two memblock_reserve() > calls at the next boot. > > On arm64 systems with 100s of CPUs, this may result in a excessive > number of memblock reservations, and needless fragmentation. > > So instead, make use of the newly updated struct linux_efi_memreserve > layout to put multiple reservations into a single linked list entry. > This should get rid of the numerous tiny memblock reservations, and > effectively cut the total number of reservations in half on arm64 > systems with many CPUs. > > Tested-by: Marc Zyngier <marc.zyngier@arm.com> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > drivers/firmware/efi/efi.c | 20 +++++++++++++++++--- > include/linux/efi.h | 3 +++ > 2 files changed, 20 insertions(+), 3 deletions(-) > > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c > index 80b11521627a..e90bc32c2670 100644 > --- a/drivers/firmware/efi/efi.c > +++ b/drivers/firmware/efi/efi.c > @@ -998,7 +998,8 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) > { > struct linux_efi_memreserve *rsv; > int rsvsize = EFI_MEMRESERVE_SIZE(1); > - int rc; > + unsigned long prsv; > + int rc, index; > > if (efi_memreserve_root == (void *)ULONG_MAX) > return -ENODEV; > @@ -1009,11 +1010,24 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) > return rc; > } > > - rsv = kmalloc(rsvsize, GFP_ATOMIC); I fixed the following build warning in this patch: drivers/firmware/efi/efi.c:1000:6: warning: unused variable ‘rsvsize’ [-Wunused-variable] 'rsvsize' got entirely orphaned by the patch, so it can be removed. Thanks, Ingo
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index 80b11521627a..e90bc32c2670 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -998,7 +998,8 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) { struct linux_efi_memreserve *rsv; int rsvsize = EFI_MEMRESERVE_SIZE(1); - int rc; + unsigned long prsv; + int rc, index; if (efi_memreserve_root == (void *)ULONG_MAX) return -ENODEV; @@ -1009,11 +1010,24 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) return rc; } - rsv = kmalloc(rsvsize, GFP_ATOMIC); + /* first try to find a slot in an existing linked list entry */ + for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) { + rsv = __va(prsv); + index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size); + if (index < rsv->size) { + rsv->entry[index].base = addr; + rsv->entry[index].size = size; + + return 0; + } + } + + /* no slot found - allocate a new linked list entry */ + rsv = (struct linux_efi_memreserve *)__get_free_page(GFP_ATOMIC); if (!rsv) return -ENOMEM; - rsv->size = 1; + rsv->size = EFI_MEMRESERVE_COUNT(PAGE_SIZE); atomic_set(&rsv->count, 1); rsv->entry[0].base = addr; rsv->entry[0].size = size; diff --git a/include/linux/efi.h b/include/linux/efi.h index 4f27640fdcdc..becd5d76a207 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1724,4 +1724,7 @@ struct linux_efi_memreserve { #define EFI_MEMRESERVE_SIZE(count) (sizeof(struct linux_efi_memreserve) + \ (count) * sizeof(((struct linux_efi_memreserve *)0)->entry[0])) +#define EFI_MEMRESERVE_COUNT(size) (((size) - sizeof(struct linux_efi_memreserve)) \ + / sizeof(((struct linux_efi_memreserve *)0)->entry[0])) + #endif /* _LINUX_EFI_H */