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a="1012079715" X-IronPort-AV: E=Sophos;i="5.98,286,1673942400"; d="scan'208";a="1012079715" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.255.30.216]) ([10.255.30.216]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Mar 2023 19:29:28 -0700 Message-ID: <6cf365a3-dddc-8b74-4d74-04666fbeb53d@intel.com> Date: Fri, 24 Mar 2023 10:29:25 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.9.0 Subject: Re: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE Content-Language: en-US To: Chao Peng , Isaku Yamahata Cc: Ackerley Tng , seanjc@google.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, pbonzini@redhat.com, corbet@lwn.net, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, arnd@arndb.de, naoya.horiguchi@nec.com, linmiaohe@huawei.com, x86@kernel.org, hpa@zytor.com, hughd@google.com, jlayton@kernel.org, bfields@fieldses.org, akpm@linux-foundation.org, shuah@kernel.org, rppt@kernel.org, steven.price@arm.com, mail@maciej.szmigiero.name, vbabka@suse.cz, vannapurve@google.com, yu.c.zhang@linux.intel.com, kirill.shutemov@linux.intel.com, 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, qperret@google.com, tabba@google.com, michael.roth@amd.com, mhocko@suse.com, wei.w.wang@intel.com References: <20230128140030.GB700688@chaop.bj.intel.com> <20230308074026.GA2183207@chaop.bj.intel.com> <20230323004131.GA214881@ls.amr.corp.intel.com> <20230324021029.GA2774613@chaop.bj.intel.com> From: Xiaoyao Li In-Reply-To: <20230324021029.GA2774613@chaop.bj.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=134.134.136.31; envelope-from=xiaoyao.li@intel.com; helo=mga06.intel.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 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, HK_RANDOM_ENVFROM=0.999, HK_RANDOM_FROM=1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 On 3/24/2023 10:10 AM, Chao Peng wrote: > On Wed, Mar 22, 2023 at 05:41:31PM -0700, Isaku Yamahata wrote: >> On Wed, Mar 08, 2023 at 03:40:26PM +0800, >> Chao Peng wrote: >> >>> On Wed, Mar 08, 2023 at 12:13:24AM +0000, Ackerley Tng wrote: >>>> Chao Peng writes: >>>> >>>>> On Sat, Jan 14, 2023 at 12:01:01AM +0000, Sean Christopherson wrote: >>>>>> On Fri, Dec 02, 2022, Chao Peng wrote: >>>>> ... >>>>>> Strongly prefer to use similar logic to existing code that detects wraps: >>>> >>>>>> mem->restricted_offset + mem->memory_size < mem->restricted_offset >>>> >>>>>> This is also where I'd like to add the "gfn is aligned to offset" >>>>>> check, though >>>>>> my brain is too fried to figure that out right now. >>>> >>>>> Used count_trailing_zeros() for this TODO, unsure we have other better >>>>> approach. >>>> >>>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >>>>> index afc8c26fa652..fd34c5f7cd2f 100644 >>>>> --- a/virt/kvm/kvm_main.c >>>>> +++ b/virt/kvm/kvm_main.c >>>>> @@ -56,6 +56,7 @@ >>>>> #include >>>>> #include >>>>> #include >>>>> +#include >>>> >>>>> #include "coalesced_mmio.h" >>>>> #include "async_pf.h" >>>>> @@ -2087,6 +2088,19 @@ static bool kvm_check_memslot_overlap(struct >>>>> kvm_memslots *slots, int id, >>>>> return false; >>>>> } >>>> >>>>> +/* >>>>> + * Return true when ALIGNMENT(offset) >= ALIGNMENT(gpa). >>>>> + */ >>>>> +static bool kvm_check_rmem_offset_alignment(u64 offset, u64 gpa) >>>>> +{ >>>>> + if (!offset) >>>>> + return true; >>>>> + if (!gpa) >>>>> + return false; >>>>> + >>>>> + return !!(count_trailing_zeros(offset) >= count_trailing_zeros(gpa)); >> >> This check doesn't work expected. For example, offset = 2GB, gpa=4GB >> this check fails. > > This case is expected to fail as Sean initially suggested[*]: > I would rather reject memslot if the gfn has lesser alignment than > the offset. I'm totally ok with this approach _if_ there's a use case. > Until such a use case presents itself, I would rather be conservative > from a uAPI perspective. > > I understand that we put tighter restriction on this but if you see such > restriction is really a big issue for real usage, instead of a > theoretical problem, then we can loosen the check here. But at that time > below code is kind of x86 specific and may need improve. > > BTW, in latest code, I replaced count_trailing_zeros() with fls64(): > return !!(fls64(offset) >= fls64(gpa)); wouldn't it be !!(ffs64(offset) <= ffs64(gpa)) ? > [*] https://lore.kernel.org/all/Y8HldeHBrw+OOZVm@google.com/ > > Chao >> I come up with the following. >> >> >From ec87e25082f0497431b732702fae82c6a05071bf Mon Sep 17 00:00:00 2001 >> Message-Id: >> From: Isaku Yamahata >> Date: Wed, 22 Mar 2023 15:32:56 -0700 >> Subject: [PATCH] KVM: Relax alignment check for restricted mem >> >> kvm_check_rmem_offset_alignment() only checks based on offset alignment >> and GPA alignment. However, the actual alignment for offset depends >> on architecture. For x86 case, it can be 1G, 2M or 4K. So even if >> GPA is aligned for 1G+, only 1G-alignment is required for offset. >> >> Without this patch, gpa=4G, offset=2G results in failure of memory slot >> creation. >> >> Fixes: edc8814b2c77 ("KVM: Require gfn be aligned with restricted offset") >> Signed-off-by: Isaku Yamahata >> --- >> arch/x86/include/asm/kvm_host.h | 15 +++++++++++++++ >> virt/kvm/kvm_main.c | 9 ++++++++- >> 2 files changed, 23 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> index 88e11dd3afde..03af44650f24 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -16,6 +16,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -143,6 +144,20 @@ >> #define KVM_HPAGE_MASK(x) (~(KVM_HPAGE_SIZE(x) - 1)) >> #define KVM_PAGES_PER_HPAGE(x) (KVM_HPAGE_SIZE(x) / PAGE_SIZE) >> >> +#define kvm_arch_required_alignment kvm_arch_required_alignment >> +static inline int kvm_arch_required_alignment(u64 gpa) >> +{ >> + int zeros = count_trailing_zeros(gpa); >> + >> + WARN_ON_ONCE(!PAGE_ALIGNED(gpa)); >> + if (zeros >= KVM_HPAGE_SHIFT(PG_LEVEL_1G)) >> + return KVM_HPAGE_SHIFT(PG_LEVEL_1G); >> + else if (zeros >= KVM_HPAGE_SHIFT(PG_LEVEL_2M)) >> + return KVM_HPAGE_SHIFT(PG_LEVEL_2M); >> + >> + return PAGE_SHIFT; >> +} >> + >> #define KVM_MEMSLOT_PAGES_TO_MMU_PAGES_RATIO 50 >> #define KVM_MIN_ALLOC_MMU_PAGES 64UL >> #define KVM_MMU_HASH_SHIFT 12 >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index c9c4eef457b0..f4ff96171d24 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -2113,6 +2113,13 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id, >> return false; >> } >> >> +#ifndef kvm_arch_required_alignment >> +__weak int kvm_arch_required_alignment(u64 gpa) >> +{ >> + return PAGE_SHIFT >> +} >> +#endif >> + >> /* >> * Return true when ALIGNMENT(offset) >= ALIGNMENT(gpa). >> */ >> @@ -2123,7 +2130,7 @@ static bool kvm_check_rmem_offset_alignment(u64 offset, u64 gpa) >> if (!gpa) >> return false; >> >> - return !!(count_trailing_zeros(offset) >= count_trailing_zeros(gpa)); >> + return !!(count_trailing_zeros(offset) >= kvm_arch_required_alignment(gpa)); >> } >> >> /* >> -- >> 2.25.1 >> >> >> >> -- >> Isaku Yamahata