From: Paul Mackerras <paulus@ozlabs.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, npiggin@gmail.com
Subject: Re: [PATCH v4 09/22] powerpc/kvm/book3s: Add helper to walk partition scoped linux page table.
Date: Thu, 28 May 2020 11:43:38 +1000 [thread overview]
Message-ID: <20200528014338.GC307798@thinks.paulus.ozlabs.org> (raw)
In-Reply-To: <20200505071729.54912-10-aneesh.kumar@linux.ibm.com>
On Tue, May 05, 2020 at 12:47:16PM +0530, Aneesh Kumar K.V wrote:
> The locking rules for walking partition scoped table is different from process
> scoped table. Hence add a helper for secondary linux page table walk and also
> add check whether we are holding the right locks.
This patch is causing new warnings to appear when testing migration,
like this:
[ 142.090159] ------------[ cut here ]------------
[ 142.090160] find_kvm_secondary_pte called with kvm mmu_lock not held
[ 142.090176] WARNING: CPU: 23 PID: 5341 at arch/powerpc/include/asm/kvm_book3s_64.h:644 kvmppc_hv_get_dirty_log_radix+0x2e4/0x340 [kvm_hv]
[ 142.090177] Modules linked in: xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables bpfilter overlay binfmt_misc input_leds raid_class scsi_transport_sas sch_fq_codel sunrpc kvm_hv kvm
[ 142.090188] CPU: 23 PID: 5341 Comm: qemu-system-ppc Tainted: G W 5.7.0-rc5-kvm-00211-g9ccf10d6d088 #432
[ 142.090189] NIP: c008000000fe848c LR: c008000000fe8488 CTR: 0000000000000000
[ 142.090190] REGS: c000001e19f077e0 TRAP: 0700 Tainted: G W (5.7.0-rc5-kvm-00211-g9ccf10d6d088)
[ 142.090191] MSR: 9000000000029033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 42222422 XER: 20040000
[ 142.090196] CFAR: c00000000012f5ac IRQMASK: 0
GPR00: c008000000fe8488 c000001e19f07a70 c008000000ffe200 0000000000000039
GPR04: 0000000000000001 c000001ffc8b4900 0000000000018840 0000000000000007
GPR08: 0000000000000003 0000000000000001 0000000000000007 0000000000000001
GPR12: 0000000000002000 c000001fff6d9400 000000011f884678 00007fff70b70000
GPR16: 00007fff7137cb90 00007fff7dcb4410 0000000000000001 0000000000000000
GPR20: 000000000ffe0000 0000000000000000 0000000000000001 0000000000000000
GPR24: 8000000000000000 0000000000000001 c000001e1f67e600 c000001e1fd82410
GPR28: 0000000000001000 c000001e2e410000 0000000000000fff 0000000000000ffe
[ 142.090217] NIP [c008000000fe848c] kvmppc_hv_get_dirty_log_radix+0x2e4/0x340 [kvm_hv]
[ 142.090223] LR [c008000000fe8488] kvmppc_hv_get_dirty_log_radix+0x2e0/0x340 [kvm_hv]
[ 142.090224] Call Trace:
[ 142.090230] [c000001e19f07a70] [c008000000fe8488] kvmppc_hv_get_dirty_log_radix+0x2e0/0x340 [kvm_hv] (unreliable)
[ 142.090236] [c000001e19f07b50] [c008000000fd42e4] kvm_vm_ioctl_get_dirty_log_hv+0x33c/0x3c0 [kvm_hv]
[ 142.090292] [c000001e19f07be0] [c008000000eea878] kvm_vm_ioctl_get_dirty_log+0x30/0x50 [kvm]
[ 142.090300] [c000001e19f07c00] [c008000000edc818] kvm_vm_ioctl+0x2b0/0xc00 [kvm]
[ 142.090302] [c000001e19f07d50] [c00000000046e148] ksys_ioctl+0xf8/0x150
[ 142.090305] [c000001e19f07da0] [c00000000046e1c8] sys_ioctl+0x28/0x80
[ 142.090307] [c000001e19f07dc0] [c00000000003652c] system_call_exception+0x16c/0x240
[ 142.090309] [c000001e19f07e20] [c00000000000d070] system_call_common+0xf0/0x278
[ 142.090310] Instruction dump:
[ 142.090312] 7d3a512a 4200ffd0 7ffefb78 4bfffdc4 60000000 3c820000 e8848468 3c620000
[ 142.090317] e86384a8 38840010 4800673d e8410018 <0fe00000> 4bfffdd4 60000000 60000000
[ 142.090322] ---[ end trace 619d45057b6919e0 ]---
Indeed, kvm_radix_test_clear_dirty() tests the PTE dirty bit
locklessly, and only takes the kvm->mmu_lock once it finds a dirty
PTE. I think that is important for performance, since on any given
scan of the guest real address space we may only find a small
proportion of the guest pages to be dirty.
Are you now relying on the kvm->mmu_lock to protect the existence of
the PTEs, or just their content?
Paul.
next prev parent reply other threads:[~2020-05-28 1:56 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 7:17 [PATCH v4 00/22] Avoid IPI while updating page table entries Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 01/22] powerpc/pkeys: Avoid using lockless page table walk Aneesh Kumar K.V
2020-05-13 8:49 ` Michael Ellerman
2020-05-05 7:17 ` [PATCH v4 02/22] powerpc/pkeys: Check vma before returning key fault error to the user Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 03/22] powerpc/mm/hash64: use _PAGE_PTE when checking for pte_present Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 04/22] powerpc/hash64: Restrict page table lookup using init_mm with __flush_hash_table_range Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 05/22] powerpc/book3s64/hash: Use the pte_t address from the caller Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 06/22] powerpc/mce: Don't reload pte val in addr_to_pfn Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 07/22] powerpc/perf/callchain: Use __get_user_pages_fast in read_user_stack_slow Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 08/22] powerpc/kvm/book3s: switch from raw_spin_*lock to arch_spin_lock Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 09/22] powerpc/kvm/book3s: Add helper to walk partition scoped linux page table Aneesh Kumar K.V
2020-05-28 1:43 ` Paul Mackerras [this message]
2020-05-28 6:01 ` Aneesh Kumar K.V
2020-05-28 7:25 ` Paul Mackerras
2020-05-05 7:17 ` [PATCH v4 10/22] powerpc/kvm/nested: Add helper to walk nested shadow " Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 11/22] powerpc/kvm/book3s: Use kvm helpers to walk shadow or secondary table Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 12/22] powerpc/kvm/book3s: Add helper for host page table walk Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 13/22] powerpc/kvm/book3s: Use find_kvm_host_pte in page fault handler Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 14/22] powerpc/kvm/book3s: Use find_kvm_host_pte in h_enter Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 15/22] powerpc/kvm/book3s: use find_kvm_host_pte in pute_tce functions Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 16/22] powerpc/kvm/book3s: Avoid using rmap to protect parallel page table update Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 17/22] powerpc/kvm/book3s: use find_kvm_host_pte in kvmppc_book3s_instantiate_page Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 18/22] powerpc/kvm/book3s: Use find_kvm_host_pte in kvmppc_get_hpa Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 19/22] powerpc/kvm/book3s: Use pte_present instead of opencoding _PAGE_PRESENT check Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 20/22] powerpc/mm/book3s64: Avoid sending IPI on clearing PMD Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 21/22] mm: change pmdp_huge_get_and_clear_full take vm_area_struct as arg Aneesh Kumar K.V
2020-05-05 7:17 ` [PATCH v4 22/22] powerpc/mm/book3s64: Fix MADV_DONTNEED and parallel page fault race Aneesh Kumar K.V
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