Commit 5fcc48d5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

x86/kvm/vmx: Fix VMX vs hrtimer_rearm_deferred() 



Vishal reported that KVM unit test 'x2apic' started failing after commit
0e98eb14 ("entry: Prepare for deferred hrtimer rearming").

The reason is that KVM/VMX is injecting interrupts while it has interrupts
disabled, for a context that will enable interrupts, this means that
regs->flags.X86_EFLAGS_IF == 0 and irqentry_exit() will not do the right
thing.

Notably, irqentry_exit() must not call hrtimer_rearm_deferred() when the return
context does not have IF set, because this will cause problems vs NMIs.

Therefore, fix up the state after the injection.

Fixes: 0e98eb14 ("entry: Prepare for deferred hrtimer rearming")
Reported-by: default avatar"Verma, Vishal L" <vishal.l.verma@intel.com>
Suggested-by: default avatarThomas Gleixner <tglx@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@kernel.org>
Tested-by: default avatar"Verma, Vishal L" <vishal.l.verma@intel.com>
Tested-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Tested-by: default avatarZhao Liu <zhao1.liu@intel.com>
Tested-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarBinbin Wu <binbin.wu@linux.intel.com>
Link: https://patch.msgid.link/20260423155936.957351833@infradead.org
Closes: https://lore.kernel.org/r/70cd3e97fbb796e2eb2ff8cd4b7614ada05a5f24.camel%40intel.com
parent 0701c9e1

arch/x86/entry/common.c

+13 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 


#include <linux/entry-common.h>

#include <linux/kvm_types.h>

#include <linux/hrtimer_rearm.h>

#include <asm/fred.h>

#include <asm/desc.h>
@@ -27,6 +28,18 @@ noinstr void x86_entry_from_kvm(unsigned int event_type, unsigned int vector) 
#else

		idt_entry_from_kvm(vector);

#endif

		/*

		 * Strictly speaking, only the NMI path requires noinstr.

		 */

		instrumentation_begin();

		/*

		 * KVM/VMX will dispatch from IRQ-disabled but for a context

		 * that will have IRQs-enabled. This confuses the entry code

		 * and it will not have reprogrammed the timer. Do so now.

		 */

		hrtimer_rearm_deferred();

		instrumentation_end();



		return;

	}