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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-46fdf0a72d4sm60457551cf.13.2025.02.04.09.09.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Feb 2025 09:09:38 -0800 (PST) Date: Tue, 4 Feb 2025 12:09:37 -0500 From: Peter Xu To: =?utf-8?Q?=E2=80=9CWilliam?= Roche Cc: david@redhat.com, kvm@vger.kernel.org, qemu-devel@nongnu.org, qemu-arm@nongnu.org, pbonzini@redhat.com, richard.henderson@linaro.org, philmd@linaro.org, peter.maydell@linaro.org, mtosatti@redhat.com, imammedo@redhat.com, eduardo@habkost.net, marcel.apfelbaum@gmail.com, wangyanan55@huawei.com, zhao1.liu@intel.com, joao.m.martins@oracle.com Subject: Re: [PATCH v7 2/6] system/physmem: poisoned memory discard on reboot Message-ID: References: <20250201095726.3768796-1-william.roche@oracle.com> <20250201095726.3768796-3-william.roche@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250201095726.3768796-3-william.roche@oracle.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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 On Sat, Feb 01, 2025 at 09:57:22AM +0000, “William Roche wrote: > From: William Roche > > Repair poisoned memory location(s), calling ram_block_discard_range(): > punching a hole in the backend file when necessary and regenerating > a usable memory. > If the kernel doesn't support the madvise calls used by this function > and we are dealing with anonymous memory, fall back to remapping the > location(s). > > Signed-off-by: William Roche > Acked-by: David Hildenbrand > --- > system/physmem.c | 58 ++++++++++++++++++++++++++++++------------------ > 1 file changed, 36 insertions(+), 22 deletions(-) > > diff --git a/system/physmem.c b/system/physmem.c > index 3dd2adde73..e8ff930bc9 100644 > --- a/system/physmem.c > +++ b/system/physmem.c > @@ -2167,6 +2167,23 @@ void qemu_ram_free(RAMBlock *block) > } > > #ifndef _WIN32 > +/* Simply remap the given VM memory location from start to start+length */ > +static int qemu_ram_remap_mmap(RAMBlock *block, uint64_t start, size_t length) > +{ > + int flags, prot; > + void *area; > + void *host_startaddr = block->host + start; > + > + assert(block->fd < 0); > + flags = MAP_FIXED | MAP_ANONYMOUS; > + flags |= block->flags & RAM_SHARED ? MAP_SHARED : MAP_PRIVATE; > + flags |= block->flags & RAM_NORESERVE ? MAP_NORESERVE : 0; > + prot = PROT_READ; > + prot |= block->flags & RAM_READONLY ? 0 : PROT_WRITE; > + area = mmap(host_startaddr, length, prot, flags, -1, 0); > + return area != host_startaddr ? -errno : 0; > +} > + > /* > * qemu_ram_remap - remap a single RAM page > * > @@ -2184,9 +2201,7 @@ void qemu_ram_remap(ram_addr_t addr) > { > RAMBlock *block; > uint64_t offset; > - int flags; > - void *area, *vaddr; > - int prot; > + void *vaddr; > size_t page_size; > > RAMBLOCK_FOREACH(block) { > @@ -2201,25 +2216,24 @@ void qemu_ram_remap(ram_addr_t addr) > ; > } else if (xen_enabled()) { > abort(); > - } else { Do we need to keep this line? Otherwise it looks to me the new code won't be executed at all in !xen.. > - flags = MAP_FIXED; > - flags |= block->flags & RAM_SHARED ? > - MAP_SHARED : MAP_PRIVATE; > - flags |= block->flags & RAM_NORESERVE ? MAP_NORESERVE : 0; > - prot = PROT_READ; > - prot |= block->flags & RAM_READONLY ? 0 : PROT_WRITE; > - if (block->fd >= 0) { > - area = mmap(vaddr, page_size, prot, flags, block->fd, > - offset + block->fd_offset); > - } else { > - flags |= MAP_ANONYMOUS; > - area = mmap(vaddr, page_size, prot, flags, -1, 0); > - } > - if (area != vaddr) { > - error_report("Could not remap RAM %s:%" PRIx64 "+%" PRIx64 > - " +%zx", block->idstr, offset, > - block->fd_offset, page_size); > - exit(1); > + if (ram_block_discard_range(block, offset, page_size) != 0) { > + /* > + * Fall back to using mmap() only for anonymous mapping, > + * as if a backing file is associated we may not be able > + * to recover the memory in all cases. > + * So don't take the risk of using only mmap and fail now. > + */ > + if (block->fd >= 0) { > + error_report("Could not remap RAM %s:%" PRIx64 "+%" > + PRIx64 " +%zx", block->idstr, offset, > + block->fd_offset, page_size); > + exit(1); > + } > + if (qemu_ram_remap_mmap(block, offset, page_size) != 0) { > + error_report("Could not remap RAM %s:%" PRIx64 " +%zx", > + block->idstr, offset, page_size); > + exit(1); > + } > } > memory_try_enable_merging(vaddr, page_size); > qemu_ram_setup_dump(vaddr, page_size); > -- > 2.43.5 > -- Peter Xu