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[109.43.177.86]) by smtp.gmail.com with ESMTPSA id z6-20020a1709063ac600b00a4636e3f576sm1471343ejd.160.2024.03.12.10.38.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Mar 2024 10:38:14 -0700 (PDT) Message-ID: <0fef1275-836f-496a-8a96-3e46c09cb232@redhat.com> Date: Tue, 12 Mar 2024 18:38:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] system/physmem: Fix migration dirty bitmap coherency with TCG memory access Content-Language: en-US To: Nicholas Piggin , qemu-devel@nongnu.org, Peter Xu , David Hildenbrand , Paolo Bonzini Cc: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , "Dr . David Alan Gilbert" References: <20240219061731.232570-1-npiggin@gmail.com> From: Thomas Huth Autocrypt: addr=thuth@redhat.com; keydata= xsFNBFH7eUwBEACzyOXKU+5Pcs6wNpKzrlJwzRl3VGZt95VCdb+FgoU9g11m7FWcOafrVRwU yYkTm9+7zBUc0sW5AuPGR/dp3pSLX/yFWsA/UB4nJsHqgDvDU7BImSeiTrnpMOTXb7Arw2a2 4CflIyFqjCpfDM4MuTmzTjXq4Uov1giGE9X6viNo1pxyEpd7PanlKNnf4PqEQp06X4IgUacW tSGj6Gcns1bCuHV8OPWLkf4hkRnu8hdL6i60Yxz4E6TqlrpxsfYwLXgEeswPHOA6Mn4Cso9O 0lewVYfFfsmokfAVMKWzOl1Sr0KGI5T9CpmRfAiSHpthhHWnECcJFwl72NTi6kUcUzG4se81 O6n9d/kTj7pzTmBdfwuOZ0YUSqcqs0W+l1NcASSYZQaDoD3/SLk+nqVeCBB4OnYOGhgmIHNW 0CwMRO/GK+20alxzk//V9GmIM2ACElbfF8+Uug3pqiHkVnKqM7W9/S1NH2qmxB6zMiJUHlTH gnVeZX0dgH27mzstcF786uPcdEqS0KJuxh2kk5IvUSL3Qn3ZgmgdxBMyCPciD/1cb7/Ahazr 3ThHQXSHXkH/aDXdfLsKVuwDzHLVSkdSnZdt5HHh75/NFHxwaTlydgfHmFFwodK8y/TjyiGZ zg2Kje38xnz8zKn9iesFBCcONXS7txENTzX0z80WKBhK+XSFJwARAQABzR5UaG9tYXMgSHV0 aCA8dGh1dGhAcmVkaGF0LmNvbT7CwXgEEwECACIFAlVgX6oCGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAAoJEC7Z13T+cC21EbIP/ii9cvT2HHGbFRl8HqGT6+7Wkb+XLMqJBMAIGiQK QIP3xk1HPTsLfVG0ao4hy/oYkGNOP8+ubLnZen6Yq3zAFiMhQ44lvgigDYJo3Ve59gfe99KX EbtB+X95ODARkq0McR6OAsPNJ7gpEUzfkQUUJTXRDQXfG/FX303Gvk+YU0spm2tsIKPl6AmV 1CegDljzjycyfJbk418MQmMu2T82kjrkEofUO2a24ed3VGC0/Uz//XCR2ZTo+vBoBUQl41BD eFFtoCSrzo3yPFS+w5fkH9NT8ChdpSlbNS32NhYQhJtr9zjWyFRf0Zk+T/1P7ECn6gTEkp5k ofFIA4MFBc/fXbaDRtBmPB0N9pqTFApIUI4vuFPPO0JDrII9dLwZ6lO9EKiwuVlvr1wwzsgq zJTPBU3qHaUO4d/8G+gD7AL/6T4zi8Jo/GmjBsnYaTzbm94lf0CjXjsOX3seMhaE6WAZOQQG tZHAO1kAPWpaxne+wtgMKthyPLNwelLf+xzGvrIKvLX6QuLoWMnWldu22z2ICVnLQChlR9d6 WW8QFEpo/FK7omuS8KvvopFcOOdlbFMM8Y/8vBgVMSsK6fsYUhruny/PahprPbYGiNIhKqz7 UvgyZVl4pBFjTaz/SbimTk210vIlkDyy1WuS8Zsn0htv4+jQPgo9rqFE4mipJjy/iboDzsFN BFH7eUwBEAC2nzfUeeI8dv0C4qrfCPze6NkryUflEut9WwHhfXCLjtvCjnoGqFelH/PE9NF4 4VPSCdvD1SSmFVzu6T9qWdcwMSaC+e7G/z0/AhBfqTeosAF5XvKQlAb9ZPkdDr7YN0a1XDfa +NgA+JZB4ROyBZFFAwNHT+HCnyzy0v9Sh3BgJJwfpXHH2l3LfncvV8rgFv0bvdr70U+On2XH 5bApOyW1WpIG5KPJlDdzcQTyptOJ1dnEHfwnABEfzI3dNf63rlxsGouX/NFRRRNqkdClQR3K gCwciaXfZ7ir7fF0u1N2UuLsWA8Ei1JrNypk+MRxhbvdQC4tyZCZ8mVDk+QOK6pyK2f4rMf/ WmqxNTtAVmNuZIwnJdjRMMSs4W4w6N/bRvpqtykSqx7VXcgqtv6eqoDZrNuhGbekQA0sAnCJ VPArerAZGArm63o39me/bRUQeQVSxEBmg66yshF9HkcUPGVeC4B0TPwz+HFcVhheo6hoJjLq knFOPLRj+0h+ZL+D0GenyqD3CyuyeTT5dGcNU9qT74bdSr20k/CklvI7S9yoQje8BeQAHtdV cvO8XCLrpGuw9SgOS7OP5oI26a0548M4KldAY+kqX6XVphEw3/6U1KTf7WxW5zYLTtadjISB X9xsRWSU+Yqs3C7oN5TIPSoj9tXMoxZkCIHWvnqGwZ7JhwARAQABwsFfBBgBAgAJBQJR+3lM AhsMAAoJEC7Z13T+cC21hPAQAIsBL9MdGpdEpvXs9CYrBkd6tS9mbaSWj6XBDfA1AEdQkBOn ZH1Qt7HJesk+qNSnLv6+jP4VwqK5AFMrKJ6IjE7jqgzGxtcZnvSjeDGPF1h2CKZQPpTw890k fy18AvgFHkVk2Oylyexw3aOBsXg6ukN44vIFqPoc+YSU0+0QIdYJp/XFsgWxnFIMYwDpxSHS 5fdDxUjsk3UBHZx+IhFjs2siVZi5wnHIqM7eK9abr2cK2weInTBwXwqVWjsXZ4tq5+jQrwDK cvxIcwXdUTLGxc4/Z/VRH1PZSvfQxdxMGmNTGaXVNfdFZjm4fz0mz+OUi6AHC4CZpwnsliGV ODqwX8Y1zic9viSTbKS01ZNp175POyWViUk9qisPZB7ypfSIVSEULrL347qY/hm9ahhqmn17 Ng255syASv3ehvX7iwWDfzXbA0/TVaqwa1YIkec+/8miicV0zMP9siRcYQkyTqSzaTFBBmqD oiT+z+/E59qj/EKfyce3sbC9XLjXv3mHMrq1tKX4G7IJGnS989E/fg6crv6NHae9Ckm7+lSs IQu4bBP2GxiRQ+NV3iV/KU3ebMRzqIC//DCOxzQNFNJAKldPe/bKZMCxEqtVoRkuJtNdp/5a yXFZ6TfE1hGKrDBYAm4vrnZ4CXFSBDllL59cFFOJCkn4Xboj/aVxxJxF30bn In-Reply-To: <20240219061731.232570-1-npiggin@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.687, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi Peter, Paolo, David, this patch fixes a problem with the kvm-unit-tests ... could we get it included in QEMU 9.0 ? Thanks, Thomas On 19/02/2024 07.17, Nicholas Piggin wrote: > The fastpath in cpu_physical_memory_sync_dirty_bitmap() to test large > aligned ranges forgot to bring the TCG TLB up to date after clearing > some of the dirty memory bitmap bits. This can result in stores though > the TCG TLB not setting the dirty memory bitmap and ultimately causes > memory corruption / lost updates during migration from a TCG host. > > Fix this by exporting an abstracted function to call when dirty bits > have been cleared. > > Fixes: aa8dc044772 ("migration: synchronize memory bitmap 64bits at a time") > Signed-off-by: Nicholas Piggin > --- > > I reproduced this with a kvm-unit-tests migration stress tester I'm > working on. Tree here with reproduce instructions in latest commit. > > https://github.com/npiggin/kvm-unit-tests/tree/qemu-tcg-migration-bug > > Thanks, > Nick > > include/exec/ram_addr.h | 13 +++++++++++++ > system/physmem.c | 14 +++++++++----- > 2 files changed, 22 insertions(+), 5 deletions(-) > > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h > index 90676093f5..dadb2deb11 100644 > --- a/include/exec/ram_addr.h > +++ b/include/exec/ram_addr.h > @@ -443,6 +443,16 @@ uint64_t cpu_physical_memory_set_dirty_lebitmap(unsigned long *bitmap, > } > #endif /* not _WIN32 */ > > +void tcg_cpu_physical_memory_dirty_bits_cleared(ram_addr_t start, > + ram_addr_t length); > +static inline void cpu_physical_memory_dirty_bits_cleared(ram_addr_t start, > + ram_addr_t length) > +{ > + if (tcg_enabled()) { > + tcg_cpu_physical_memory_dirty_bits_cleared(start, length); > + } > + > +} > bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t start, > ram_addr_t length, > unsigned client); > @@ -504,6 +514,9 @@ uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb, > idx++; > } > } > + if (num_dirty) { > + cpu_physical_memory_dirty_bits_cleared(start, length); > + } > > if (rb->clear_bmap) { > /* > diff --git a/system/physmem.c b/system/physmem.c > index 5e66d9ae36..dc0d8b16aa 100644 > --- a/system/physmem.c > +++ b/system/physmem.c > @@ -839,6 +839,12 @@ static void tlb_reset_dirty_range_all(ram_addr_t start, ram_addr_t length) > } > } > > +void tcg_cpu_physical_memory_dirty_bits_cleared(ram_addr_t start, > + ram_addr_t length) > +{ > + tlb_reset_dirty_range_all(start, length); > +} > + > /* Note: start and end must be within the same ram block. */ > bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t start, > ram_addr_t length, > @@ -881,8 +887,8 @@ bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t start, > memory_region_clear_dirty_bitmap(ramblock->mr, mr_offset, mr_size); > } > > - if (dirty && tcg_enabled()) { > - tlb_reset_dirty_range_all(start, length); > + if (dirty) { > + cpu_physical_memory_dirty_bits_cleared(start, length); > } > > return dirty; > @@ -929,9 +935,7 @@ DirtyBitmapSnapshot *cpu_physical_memory_snapshot_and_clear_dirty > } > } > > - if (tcg_enabled()) { > - tlb_reset_dirty_range_all(start, length); > - } > + cpu_physical_memory_dirty_bits_cleared(start, length); > > memory_region_clear_dirty_bitmap(mr, offset, length); >