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Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, wei.w.wang@intel.com Subject: Re: [PATCH v10 4/9] KVM: Add KVM_EXIT_MEMORY_FAULT exit Message-ID: <20221207151153.GE1275553@chaop.bj.intel.com> Reply-To: Chao Peng References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-5-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E9AD210000F X-Stat-Signature: ff8ou8szmcha4z8xtws6s3pr5mcxjz4p X-Spamd-Result: default: False [-5.70 / 9.00]; BAYES_HAM(-6.00)[100.00%]; SUBJECT_HAS_UNDERSCORES(1.00)[]; DMARC_POLICY_ALLOW(-0.50)[intel.com,none]; R_DKIM_ALLOW(-0.20)[intel.com:s=Intel]; MIME_GOOD(-0.10)[text/plain]; RCVD_NO_TLS_LAST(0.10)[]; RCPT_COUNT_TWELVE(0.00)[48]; R_SPF_NA(0.00)[no SPF record]; FROM_EQ_ENVFROM(0.00)[]; DKIM_TRACE(0.00)[intel.com:+]; MID_RHS_MATCH_FROMTLD(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; MIME_TRACE(0.00)[0:+]; FROM_HAS_DN(0.00)[]; REPLYTO_EQ_FROM(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_SOME(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; ARC_NA(0.00)[]; HAS_REPLYTO(0.00)[chao.p.peng@linux.intel.com] X-Rspam-User: X-HE-Tag: 1670426185-899553 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Dec 06, 2022 at 03:47:20PM +0000, Fuad Tabba wrote: > Hi, > > On Fri, Dec 2, 2022 at 6:19 AM Chao Peng wrote: > > > > This new KVM exit allows userspace to handle memory-related errors. It > > indicates an error happens in KVM at guest memory range [gpa, gpa+size). > > The flags includes additional information for userspace to handle the > > error. Currently bit 0 is defined as 'private memory' where '1' > > indicates error happens due to private memory access and '0' indicates > > error happens due to shared memory access. > > > > When private memory is enabled, this new exit will be used for KVM to > > exit to userspace for shared <-> private memory conversion in memory > > encryption usage. In such usage, typically there are two kind of memory > > conversions: > > - explicit conversion: happens when guest explicitly calls into KVM > > to map a range (as private or shared), KVM then exits to userspace > > to perform the map/unmap operations. > > - implicit conversion: happens in KVM page fault handler where KVM > > exits to userspace for an implicit conversion when the page is in a > > different state than requested (private or shared). > > > > Suggested-by: Sean Christopherson > > Co-developed-by: Yu Zhang > > Signed-off-by: Yu Zhang > > Signed-off-by: Chao Peng > > Reviewed-by: Fuad Tabba > > --- > > Documentation/virt/kvm/api.rst | 22 ++++++++++++++++++++++ > > include/uapi/linux/kvm.h | 8 ++++++++ > > 2 files changed, 30 insertions(+) > > > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > > index 99352170c130..d9edb14ce30b 100644 > > --- a/Documentation/virt/kvm/api.rst > > +++ b/Documentation/virt/kvm/api.rst > > @@ -6634,6 +6634,28 @@ array field represents return values. The userspace should update the return > > values of SBI call before resuming the VCPU. For more details on RISC-V SBI > > spec refer, https://github.com/riscv/riscv-sbi-doc. > > > > +:: > > + > > + /* KVM_EXIT_MEMORY_FAULT */ > > + struct { > > + #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 0) > > + __u64 flags; > > I see you've removed the padding and increased the flag size. Yes Sean suggested this and also looks good to me. Chao > > Reviewed-by: Fuad Tabba > Tested-by: Fuad Tabba > > Cheers, > /fuad > > > > > > + __u64 gpa; > > + __u64 size; > > + } memory; > > + > > +If exit reason is KVM_EXIT_MEMORY_FAULT then it indicates that the VCPU has > > +encountered a memory error which is not handled by KVM kernel module and > > +userspace may choose to handle it. The 'flags' field indicates the memory > > +properties of the exit. > > + > > + - KVM_MEMORY_EXIT_FLAG_PRIVATE - indicates the memory error is caused by > > + private memory access when the bit is set. Otherwise the memory error is > > + caused by shared memory access when the bit is clear. > > + > > +'gpa' and 'size' indicate the memory range the error occurs at. The userspace > > +may handle the error and return to KVM to retry the previous memory access. > > + > > :: > > > > /* KVM_EXIT_NOTIFY */ > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > index 13bff963b8b0..c7e9d375a902 100644 > > --- a/include/uapi/linux/kvm.h > > +++ b/include/uapi/linux/kvm.h > > @@ -300,6 +300,7 @@ struct kvm_xen_exit { > > #define KVM_EXIT_RISCV_SBI 35 > > #define KVM_EXIT_RISCV_CSR 36 > > #define KVM_EXIT_NOTIFY 37 > > +#define KVM_EXIT_MEMORY_FAULT 38 > > > > /* For KVM_EXIT_INTERNAL_ERROR */ > > /* Emulate instruction failed. */ > > @@ -541,6 +542,13 @@ struct kvm_run { > > #define KVM_NOTIFY_CONTEXT_INVALID (1 << 0) > > __u32 flags; > > } notify; > > + /* KVM_EXIT_MEMORY_FAULT */ > > + struct { > > +#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 0) > > + __u64 flags; > > + __u64 gpa; > > + __u64 size; > > + } memory; > > /* Fix the size of the union. */ > > char padding[256]; > > }; > > -- > > 2.25.1 > >