| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Tue, 29 Mar 2016 17:57:55 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org Cc: dmatlack@...gle.com Subject: [PATCH] KVM: x86: reduce default value of halt_poll_ns parameter Windows lets applications choose the frequency of the timer tick, and in Windows 10 the maximum rate was changed from 1024 Hz to 2048 Hz. Unfortunately, because of the way the Windows API works, most applications who need a higher rate than the default 64 Hz will just do timeGetDevCaps(&tc, sizeof(tc)); timeBeginPeriod(tc.wPeriodMin); and pick the maximum rate. This causes very high CPU usage when playing media or games on Windows 10, even if the guest does not actually use the CPU very much, because the frequent timer tick causes halt_poll_ns to kick in. There is no really good solution, especially because Microsoft could sooner or later bump the limit to 4096 Hz, but for now the best we can do is lower a bit the upper limit for halt_poll_ns. :-( Reported-by: Jon Panozzo <jonp@...e-technology.com> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com> --- arch/x86/include/asm/kvm_host.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index f62a9f37f79f..b7e394485a5f 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -43,7 +43,7 @@ #define KVM_PIO_PAGE_OFFSET 1 #define KVM_COALESCED_MMIO_PAGE_OFFSET 2 -#define KVM_HALT_POLL_NS_DEFAULT 500000 +#define KVM_HALT_POLL_NS_DEFAULT 400000 #define KVM_IRQCHIP_NUM_PINS KVM_IOAPIC_NUM_PINS -- 1.8.3.1
Powered by blists - more mailing lists