| Message ID | 20170316172243.GE14076@potion (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Mar 16, 2017 at 06:22:44PM +0100, Radim Krčmář wrote: > 2017-03-16 12:47-0400, Gabriel L. Somlo: > > On Thu, Mar 16, 2017 at 05:01:58PM +0100, Radim Krčmář wrote: > > > 2017-03-16 16:35+0100, Radim Krčmář: > > > > 2017-03-16 10:58-0400, Gabriel L. Somlo: > > > >> The intel manual said the same thing back in 2010 as well. However, > > > >> regardless of how any flags were set, interrupt-window exiting or not, > > > >> "normal" L1 MWAIT behavior was that it woke up immediately regardless. > > > >> Remember, never going to sleep is still correct ("normal" ?) behavior > > > >> per the ISA definition of MWAIT :) > > > > > > > > I'll write a simple kvm-unit-test to better understand why it is broken > > > > for you ... > > > > > > Please get git://git.kernel.org/pub/scm/virt/kvm/kvm-unit-tests.git > > > > > > and try this, thanks! > > > > > > ---8<--- > > > x86/mwait: crappy test > > > > > > `./configure && make` to build it, then follow the comment in code to > > > try few cases. > > > > kvm-unit-tests]$ time TIMEOUT=20 ./x86-run x86/mwait.flat -append '0 1 1' > > timeout -k 1s --foreground 20 qemu-kvm -nodefaults -enable-kvm -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -kernel x86/mwait.flat -append 0 1 1 > > enabling apic > > PASS: resumed from mwait 10000 times > > SUMMARY: 1 tests > > > > real 0m10.564s > > user 0m10.339s > > sys 0m0.225s > > > > > > and > > > > kvm-unit-tests]$ time TIMEOUT=20 ./x86-run x86/mwait.flat -append '0 1 0' > > timeout -k 1s --foreground 20 qemu-kvm -nodefaults -enable-kvm -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -kernel x86/mwait.flat -append 0 1 0 > > enabling apic > > PASS: resumed from mwait 10000 times > > SUMMARY: 1 tests > > > > real 0m0.746s > > user 0m0.555s > > sys 0m0.200s > > > > Both of these with Michael's v5 patch applied, on the MacPro1,1. > > > > Similar behavior (0 1 1 takes 10 seconds, 0 1 0 returns immediately) > > on the macbook air. > > > > If I revert to the original (nop-emulated MWAIT) kvm source, I get > > both versions to return immediately. > > Those look normal ... maybe MWAIT just ignores writes to the monitored > area? > > Please apply the patch below and following and try: > > time TIMEOUT=20 ./x86-run x86/mwait.flat -append '0 1 1' -smp 2 timeout -k 1s --foreground 20 qemu-kvm -nodefaults -enable-kvm -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -kernel x86/mwait.flat -append 0 1 1 -smp 2 enabling apic enabling apic PASS: resumed from mwait 10000 times SUMMARY: 1 tests real 0m0.758s user 0m0.557s sys 0m0.220s > time TIMEOUT=20 ./x86-run x86/mwait.flat -append '0 0 1' -smp 2 timeout -k 1s --foreground 20 qemu-kvm -nodefaults -enable-kvm -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -kernel x86/mwait.flat -append 0 0 1 -smp 2 enabling apic enabling apic PASS: resumed from mwait 10000 times SUMMARY: 1 tests real 0m0.748s user 0m0.550s sys 0m0.210s > time TIMEOUT=20 ./x86-run x86/mwait.flat -append '0 0 0' -smp 2 timeout -k 1s --foreground 20 qemu-kvm -nodefaults -enable-kvm -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -kernel x86/mwait.flat -append 0 0 0 -smp 2 enabling apic enabling apic PASS: resumed from mwait 10000 times SUMMARY: 1 tests real 0m0.745s user 0m0.558s sys 0m0.203s > > All of them should take rougly the same time as the NOP one, > > time TIMEOUT=20 ./x86-run x86/mwait.flat -append '0 1 0' -smp 2 They all *did* return fast, as you expected. > ---8<--- > diff --git a/x86/mwait.c b/x86/mwait.c > index c21dab5cc97d..ca38e7223596 100644 > --- a/x86/mwait.c > +++ b/x86/mwait.c > @@ -1,7 +1,9 @@ > #include "vm.h" > +#include "smp.h" > > #define TARGET_RESUMES 10000 > volatile unsigned page[4096 / 4]; > +volatile unsigned resumes; > > /* > * Execute > @@ -18,19 +20,39 @@ volatile unsigned page[4096 / 4]; > * Getting killed by the TIMEOUT most likely means that you have different HZ, > * but could also be a bug ... > */ > +void writer(void *null) > +{ > + int i; > + unsigned old_resumes = 0, new_resumes; > + > + for (i = 0; i < TARGET_RESUMES; i++) { > + (*page)++; > + > + while (old_resumes == (new_resumes = resumes)) > + pause(); > + old_resumes = new_resumes; > + } > +} > + > int main(int argc, char **argv) > { > uint32_t eax = atol(argv[1]); > uint32_t ecx = atol(argv[2]); > bool sti = atol(argv[3]); > - unsigned resumes = 0; > + bool smp; > + > + smp_init(); > + smp = cpu_count() > 1; > + > + if (smp) > + on_cpu_async(1, writer, NULL); > > if (sti) > asm volatile ("sti"); > else > asm volatile ("cli"); > > - while (resumes < TARGET_RESUMES) { > + while ((smp ? *page : resumes) < TARGET_RESUMES) { > asm volatile("monitor" :: "a" (page), "c" (0), "d" (0)); > asm volatile("mwait" :: "a" (eax), "c" (ecx)); > resumes++;
diff --git a/x86/mwait.c b/x86/mwait.c index c21dab5cc97d..ca38e7223596 100644 --- a/x86/mwait.c +++ b/x86/mwait.c @@ -1,7 +1,9 @@ #include "vm.h" +#include "smp.h" #define TARGET_RESUMES 10000 volatile unsigned page[4096 / 4]; +volatile unsigned resumes; /* * Execute @@ -18,19 +20,39 @@ volatile unsigned page[4096 / 4]; * Getting killed by the TIMEOUT most likely means that you have different HZ, * but could also be a bug ... */ +void writer(void *null) +{ + int i; + unsigned old_resumes = 0, new_resumes; + + for (i = 0; i < TARGET_RESUMES; i++) { + (*page)++; + + while (old_resumes == (new_resumes = resumes)) + pause(); + old_resumes = new_resumes; + } +} + int main(int argc, char **argv) { uint32_t eax = atol(argv[1]); uint32_t ecx = atol(argv[2]); bool sti = atol(argv[3]); - unsigned resumes = 0; + bool smp; + + smp_init(); + smp = cpu_count() > 1; + + if (smp) + on_cpu_async(1, writer, NULL); if (sti) asm volatile ("sti"); else asm volatile ("cli"); - while (resumes < TARGET_RESUMES) { + while ((smp ? *page : resumes) < TARGET_RESUMES) { asm volatile("monitor" :: "a" (page), "c" (0), "d" (0)); asm volatile("mwait" :: "a" (eax), "c" (ecx)); resumes++;