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powerpc/pseries: Add KVM guest doorbell restrictions

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KVM guests have certain restrictions and performance quirks when using
doorbells. This patch moves the EPAPR KVM guest test so it can be shared
with PSERIES, and uses that in doorbell setup code to apply the KVM
guest quirks and  improves IPI performance for two cases:

 - PowerVM guests may now use doorbells even if they are secure.

 - KVM guests no longer use doorbells if XIVE is available.

There is a valid complaint that "KVM guest" is not a very reasonable
thing to test for, it's preferable for the hypervisor to advertise
particular behaviours to the guest so they could change if the
hypervisor implementation or configuration changes. However in this case
we were already assuming a KVM guest worst case, so this patch is about
containing those quirks. If KVM later advertises fast doorbells, we
should test for that and override the quirks.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200726035155.1424103-4-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin
2020-07-26 13:51:55 +10:00
committed by Michael Ellerman
parent 5b06d1679f
commit 107c55005f
5 changed files with 53 additions and 41 deletions
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5
arch/powerpc/kernel/Makefile
View File

@@ -45,11 +45,10 @@ obj-y := cputable.o syscalls.o \
signal.o sysfs.o cacheinfo.o time.o \
prom.o traps.o setup-common.o \
udbg.o misc.o io.o misc_$(BITS).o \
of_platform.o prom_parse.o
of_platform.o prom_parse.o firmware.o
obj-y += ptrace/
obj-$(CONFIG_PPC64) += setup_64.o \
paca.o nvram_64.o firmware.o note.o \
syscall_64.o
paca.o nvram_64.o note.o syscall_64.o
obj-$(CONFIG_COMPAT) += sys_ppc32.o signal_32.o
obj-$(CONFIG_VDSO32) += vdso32/
obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o

19
arch/powerpc/kernel/firmware.c
View File

@@ -11,8 +11,27 @@
#include <linux/export.h>
#include <linux/cache.h>
#include <linux/of.h>
#include <asm/firmware.h>
#ifdef CONFIG_PPC64
unsigned long powerpc_firmware_features __read_mostly;
EXPORT_SYMBOL_GPL(powerpc_firmware_features);
#endif
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
bool is_kvm_guest(void)
{
struct device_node *hyper_node;
hyper_node = of_find_node_by_path("/hypervisor");
if (!hyper_node)
return 0;
if (!of_device_is_compatible(hyper_node, "linux,kvm"))
return 0;
return 1;
}
#endif