riscv/qemu: QEMU main repository: Please see https://www.qemu.org/docs/master/devel/submitting-a-patch.html for how to submit changes to QEMU. Pull Requests are ignored. Please only use release tarballs from the QEMU website. http://www.qemu.org - qemu

QEMU main repository: Please see https://www.qemu.org/docs/master/devel/submitting-a-patch.html for how to submit changes to QEMU. Pull Requests are ignored. Please only use release tarballs from the QEMU website. http://www.qemu.org

emulation kvm qemu virtualization

History

Maciej S. Szmigiero f6b5f71f04 target/i386: Reset parked vCPUs together with the online ones Commit `3f2a05b31e` ("target/i386: Reset TSCs of parked vCPUs too on VM reset") introduced a way to reset TSCs of parked vCPUs during VM reset to prevent them getting desynchronized with the online vCPUs and therefore causing the KVM PV clock to lose PVCLOCK_TSC_STABLE_BIT. The way this was done was by registering a parked vCPU-specific QEMU reset callback via qemu_register_reset(). However, it turns out that on particularly device-rich VMs QEMU reset callbacks can take a long time to execute (which isn't surprising, considering that they involve resetting all of VM devices). In particular, their total runtime can exceed the 1-second TSC synchronization window introduced in KVM commit 5d3cb0f6a8e3 ("KVM: Improve TSC offset matching"). Since the TSCs of online vCPUs are only reset from "synchronize_post_reset" AccelOps handler (which runs after all qemu_register_reset() handlers) this essentially makes that fix ineffective on these VMs. The easiest way to guarantee that these parked vCPUs are reset at the same time as the online ones (regardless how long it takes for VM devices to reset) is to piggyback on post-reset vCPU synchronization handler for one of online vCPUs - as there is no generic post-reset AccelOps handler that isn't per-vCPU. The first online vCPU was selected for that since it is easily available under "first_cpu" define. This does not create an ordering issue since the order of vCPU TSC resets does not matter. Fixes: `3f2a05b31e` ("target/i386: Reset TSCs of parked vCPUs too on VM reset") Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> Link: https://lore.kernel.org/r/e8b85a5915f79aa177ca49eccf0e9b534470c1cd.1743099810.git.maciej.szmigiero@oracle.com Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		1 year ago
..
hvf	accel: Forward-declare AccelOpsClass in 'qemu/typedefs.h'	1 year ago
kvm	target/i386: Reset parked vCPUs together with the online ones	1 year ago
qtest	accel: Forward-declare AccelOpsClass in 'qemu/typedefs.h'	1 year ago
stubs	gdbstub: Check for TCG before calling tb_flush()	1 year ago
tcg	accel: Prefer cached CpuClass over CPU_GET_CLASS() macro	1 year ago
xen	accel: Forward-declare AccelOpsClass in 'qemu/typedefs.h'	1 year ago
Kconfig	hw/xen: Link XenPVH with GPEX PCIe bridge	1 year ago
accel-blocker.c	include: Rename sysemu/ -> system/	2 years ago
accel-system.c	accel: Forward-declare AccelOpsClass in 'qemu/typedefs.h'	1 year ago
accel-system.h	accel: Rename accel_init_ops_interfaces() to include 'system'	3 years ago
accel-target.c	accel: Prefer cached CpuClass over CPU_GET_CLASS() macro	1 year ago
accel-user.c	accel: extend AccelState and AccelClass to user-mode	6 years ago
dummy-cpus.c	include: Rename sysemu/ -> system/	2 years ago
meson.build	accel: Rename accel_softmmu* -> accel_system*	3 years ago