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X-IronPort-AV: E=McAfee;i="6500,9779,10642"; a="363727040" X-IronPort-AV: E=Sophos;i="5.98,243,1673942400"; d="scan'208";a="363727040" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Mar 2023 23:48:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10642"; a="745821383" X-IronPort-AV: E=Sophos;i="5.98,243,1673942400"; d="scan'208";a="745821383" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.192.105]) by fmsmga004.fm.intel.com with ESMTP; 07 Mar 2023 23:48:04 -0800 Date: Wed, 8 Mar 2023 15:40:26 +0800 From: Chao Peng To: Ackerley Tng Cc: 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 Subject: Re: [PATCH v10 9/9] KVM: Enable and expose KVM_MEM_PRIVATE Message-ID: <20230308074026.GA2183207@chaop.bj.intel.com> Reply-To: Chao Peng References: <20230128140030.GB700688@chaop.bj.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C040740005 X-Stat-Signature: 5fmnerufi5uh7i4n53ssyoq4nqfzdpdf X-HE-Tag: 1678261697-204480 X-HE-Meta: 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 87YuVctS OdWytkqPZmUNbNRi9glcB0+0lWVNQHHNNA95HVCNbUOtzSNUtzJGrJRlHMDofHlkNyTtAB9GFNURq/xSRYS8cETDcU6iBbci/zsQiMHYcr+g6f5IgeXT5LyfRqAdJIIv32WhEyH+yfCQLu4CwSpfrjHzDfA0oQYmfhdnaB7VDsq7TC+3BrWtVEUeOZ4aaeslnkQakaBfdHWH82tcTcPMaXmtSXSvk6phqJdAqbjJ2Tgw9oxWtMGpudLLtJ2HVQbK3LR8kobvlKh0xDUVdaucoQ7DI8XRfe3AbhxJ4WrkgfBU/ibNIxTUO8rbu++zxBhUc0o7EuBbuUsKLksl5caDa60VsIbnKLQ4ZRHpkfvdZb5I/QVng6KLXXL/4nrxsPO2em2vl+1K6Jb+AI9SzGW2u/pDhRw== 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 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)); > > Perhaps we could do something like > > #define lowest_set_bit(val) (val & -val) > > and use > > return lowest_set_bit(offset) >= lowest_set_bit(gpa); I see kernel already has fls64(), that looks what we need ;) > > Please help me to understand: why must ALIGNMENT(offset) >= > ALIGNMENT(gpa)? Why is it not sufficient to have both gpa and offset be > aligned to PAGE_SIZE? Yes, it's sufficient. Here we just want to be conservative on the uAPI as Sean explained this at [1]: 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. [1] https://lore.kernel.org/all/Y8HldeHBrw+OOZVm@google.com/ Chao > > > +} > > + > > /* > > * Allocate some memory and give it an address in the guest physical > > address > > * space. > > @@ -2128,7 +2142,8 @@ int __kvm_set_memory_region(struct kvm *kvm, > > if (mem->flags & KVM_MEM_PRIVATE && > > (mem->restrictedmem_offset & (PAGE_SIZE - 1) || > > mem->restrictedmem_offset + mem->memory_size < > > mem->restrictedmem_offset || > > - 0 /* TODO: require gfn be aligned with restricted offset */)) > > + !kvm_check_rmem_offset_alignment(mem->restrictedmem_offset, > > + mem->guest_phys_addr))) > > return -EINVAL; > > if (as_id >= kvm_arch_nr_memslot_as_ids(kvm) || id >= KVM_MEM_SLOTS_NUM) > > return -EINVAL;