audk/OvmfPkg/8254TimerDxe
Igor Druzhinin 239b50a863 OvmfPkg: End timer interrupt later to avoid stack overflow under load
RestoreTPL called while at TPL_HIGH_LEVEL unconditionally enables
interrupts even if called in interrupt handler. That opens a window while
interrupt is not completely handled but another interrupt could be
accepted.

If a VM starts on a heavily loaded host hundreds of periodic timer
interrupts might be queued while vCPU is descheduled (the behavior is
typical for a Xen host). The next time vCPU is scheduled again all of them
get delivered back to back causing OVMF to accept each one without
finishing a previous one and cleaning up the stack. That quickly results
in stack overflow and a triple fault.

Fix it by postponing sending EOI until we finished processing the current
tick giving interrupt handler opportunity to clean up the stack before
accepting the next tick.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Message-Id: <1592275782-9369-1-git-send-email-igor.druzhinin@citrix.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2815
Acked-by: Laszlo Ersek <lersek@redhat.com>
[lersek@redhat.com: add BZ ref; rewrap msg to silence PatchCheck.py]
2020-06-18 10:20:39 +00:00
..
8254Timer.inf OvmfPkg/8254TimerDxe: Update to make it build for OVMF 2019-04-11 08:57:29 +08:00
Timer.c OvmfPkg: End timer interrupt later to avoid stack overflow under load 2020-06-18 10:20:39 +00:00
Timer.h OvmfPkg: Copy 8254TimerDxe driver from PcAtChipsetPkg 2019-04-11 08:57:29 +08:00
Timer.uni OvmfPkg: Copy 8254TimerDxe driver from PcAtChipsetPkg 2019-04-11 08:57:29 +08:00
TimerExtra.uni OvmfPkg: Copy 8254TimerDxe driver from PcAtChipsetPkg 2019-04-11 08:57:29 +08:00