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17 May 2024, 11:00:25 UTC
Revision 9a6e7c39810e4a8bc7fc95056cefb40583fe07ef authored by Wanpeng Li on 14 September 2017, 10:54:16 UTC, committed by Radim Krčmář on 14 September 2017, 16:43:43 UTC 
KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously
 
qemu-system-x86-8600  [004] d..1  7205.687530: kvm_entry: vcpu 2
qemu-system-x86-8600  [004] ....  7205.687532: kvm_exit: reason EXCEPTION_NMI rip 0xffffffffa921297d info ffffeb2c0e44e018 80000b0e
qemu-system-x86-8600  [004] ....  7205.687532: kvm_page_fault: address ffffeb2c0e44e018 error_code 0
qemu-system-x86-8600  [004] ....  7205.687620: kvm_try_async_get_page: gva = 0xffffeb2c0e44e018, gfn = 0x427e4e
qemu-system-x86-8600  [004] .N..  7205.687628: kvm_async_pf_not_present: token 0x8b002 gva 0xffffeb2c0e44e018
    kworker/4:2-7814  [004] ....  7205.687655: kvm_async_pf_completed: gva 0xffffeb2c0e44e018 address 0x7fcc30c4e000
qemu-system-x86-8600  [004] ....  7205.687703: kvm_async_pf_ready: token 0x8b002 gva 0xffffeb2c0e44e018
qemu-system-x86-8600  [004] d..1  7205.687711: kvm_entry: vcpu 2

After running some memory intensive workload in guest, I catch the kworker
which completes the GUP too quickly, and queues an "Page Ready" #PF exception
after the "Page not Present" exception before the next vmentry as the above
trace which will result in #DF injected to guest.

This patch fixes it by clearing the queue for "Page not Present" if "Page Ready"
occurs before the next vmentry since the GUP has already got the required page
and shadow page table has already been fixed by "Page Ready" handler.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Fixes: 7c90705bf2a3 ("KVM: Inject asynchronous page fault into a PV guest if page is swapped out.")
[Changed indentation and added clearing of injected. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
1 parent 648d453
Raw File
Tip revision: 9a6e7c39810e4a8bc7fc95056cefb40583fe07ef authored by Wanpeng Li on 14 September 2017, 10:54:16 UTC
KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously
Tip revision: 9a6e7c3
pnode.h 
/*
 *  linux/fs/pnode.h
 *
 * (C) Copyright IBM Corporation 2005.
 *	Released under GPL v2.
 *
 */
#ifndef _LINUX_PNODE_H
#define _LINUX_PNODE_H

#include <linux/list.h>
#include "mount.h"

#define IS_MNT_SHARED(m) ((m)->mnt.mnt_flags & MNT_SHARED)
#define IS_MNT_SLAVE(m) ((m)->mnt_master)
#define IS_MNT_NEW(m)  (!(m)->mnt_ns)
#define CLEAR_MNT_SHARED(m) ((m)->mnt.mnt_flags &= ~MNT_SHARED)
#define IS_MNT_UNBINDABLE(m) ((m)->mnt.mnt_flags & MNT_UNBINDABLE)
#define IS_MNT_MARKED(m) ((m)->mnt.mnt_flags & MNT_MARKED)
#define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED)
#define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED)
#define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED)

#define CL_EXPIRE    		0x01
#define CL_SLAVE     		0x02
#define CL_COPY_UNBINDABLE	0x04
#define CL_MAKE_SHARED 		0x08
#define CL_PRIVATE 		0x10
#define CL_SHARED_TO_SLAVE	0x20
#define CL_UNPRIVILEGED		0x40
#define CL_COPY_MNT_NS_FILE	0x80

#define CL_COPY_ALL		(CL_COPY_UNBINDABLE | CL_COPY_MNT_NS_FILE)

static inline void set_mnt_shared(struct mount *mnt)
{
	mnt->mnt.mnt_flags &= ~MNT_SHARED_MASK;
	mnt->mnt.mnt_flags |= MNT_SHARED;
}

void change_mnt_propagation(struct mount *, int);
int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
		struct hlist_head *);
int propagate_umount(struct list_head *);
int propagate_mount_busy(struct mount *, int);
void propagate_mount_unlock(struct mount *);
void mnt_release_group_id(struct mount *);
int get_dominating_id(struct mount *mnt, const struct path *root);
unsigned int mnt_get_count(struct mount *mnt);
void mnt_set_mountpoint(struct mount *, struct mountpoint *,
			struct mount *);
void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp,
			   struct mount *mnt);
struct mount *copy_tree(struct mount *, struct dentry *, int);
bool is_path_reachable(struct mount *, struct dentry *,
			 const struct path *root);
int count_mounts(struct mnt_namespace *ns, struct mount *mnt);
#endif /* _LINUX_PNODE_H */
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