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Fri, 23 May 2025 12:36:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFFJKxqzX44nUMqHLBCLT+KOS9BdkBLIZeUURW51Zp0jpVCGq7Lz+5dSD9ytJb95co0Y6Sxbg== X-Received: by 2002:a05:620a:3711:b0:7c5:aec7:7ecc with SMTP id af79cd13be357-7ceecba7654mr76804085a.13.1748028983347; Fri, 23 May 2025 12:36:23 -0700 (PDT) Received: from [192.168.40.164] ([70.105.235.240]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7cd468ccd94sm1220015185a.109.2025.05.23.12.36.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 May 2025 12:36:22 -0700 (PDT) Message-ID: <9b429da4-8db6-407e-9721-178e01fd1ebb@redhat.com> Date: Fri, 23 May 2025 15:36:16 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/5] KVM: arm64: New function to determine hardware cache management support From: Donald Dutile To: ankita@nvidia.com, jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, shahuang@redhat.com, lpieralisi@kernel.org, david@redhat.com Cc: aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, kjaju@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, zhiw@nvidia.com, mochs@nvidia.com, udhoke@nvidia.com, dnigam@nvidia.com, alex.williamson@redhat.com, sebastianene@google.com, coltonlewis@google.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, gshan@redhat.com, linux-mm@kvack.org, tabba@google.com, qperret@google.com, seanjc@google.com, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maobibo@loongson.cn References: <20250523154445.3779-1-ankita@nvidia.com> <20250523154445.3779-3-ankita@nvidia.com> <9ffc7686-0dc0-4978-8cd8-f12a1c148b63@redhat.com> In-Reply-To: <9ffc7686-0dc0-4978-8cd8-f12a1c148b63@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: O8m-lpZmvOuB90hV2OAAqbggkwRlmowovKsNqAIOqG0_1748028984 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 3CADFC0007 X-Stat-Signature: bjs15booxqxyxfqmit18i5sm7neuef3h X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1748028988-572726 X-HE-Meta: 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 j5UerS2r fcWSs4MEGQ/0hSiI0fdGxgRPA4cvkIsT7mYkjZ15wcDHYvB17ps1taz00OCaMq5xtsrqPa15Sn2BstJEK7tlTFo1dx+Ch4NLRsVsUF68lVYj9StICFlEHDajGoNSpRmoza21Cwe6q4C+7qIiWkwtHng+ujhhUx18Ob7fgZ2vNcDkAJJY2gLVdCIvUVe8E+XlTlStEt4INP6HxtX0KyCPSqOPmLMSTwhWZJPBnLCkg0fmusJ7RFCcEIUiZfVMBC25XSU7TCWn70hwXvBTqdZIWiccedH87xNaMy2Xy1BOXzWuFZhIEotVaZ5tf2LmdME79XwpoSPXMPixfar8Qn/6wlFM5P9cixh9Ay+LgdSZtLfZst6bfzBcfYnBdyUr96IT0xafZMQaDShSajd9NkmeG1b1ZEBMFbWl+oBfx7TtGQgGP3nSBSNMcB2YGt6eklzfoOCrMjtnszzWK4No= 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: List-Subscribe: List-Unsubscribe: On 5/23/25 3:30 PM, Donald Dutile wrote: > > > On 5/23/25 11:44 AM, ankita@nvidia.com wrote: >> From: Ankit Agrawal >> >> The hardware supports safely mapping PFNMAP as cacheable if it >> is capable of managing cache. This can be determined by the presence >> of FWB (Force Write Back) and CACHE_DIC feature. >> >> When FWB is not enabled, the kernel expects to trivially do cache >> management by flushing the memory by linearly converting a kvm_pte to >> phys_addr to a KVA. The cache management thus relies on memory being >> mapped. Since the GPU device memory is not kernel mapped, exit when >> the FWB is not supported. Similarly, ARM64_HAS_CACHE_DIC allows KVM >> to avoid flushing the icache and turns icache_inval_pou() into a NOP. >> So the cacheable PFNMAP is contingent on these two hardware features. >> >> Introduce a new function to make the check for presence of those >> features. >> >> CC: David Hildenbrand >> Signed-off-by: Ankit Agrawal >> --- >>   arch/arm64/kvm/mmu.c     | 12 ++++++++++++ >>   include/linux/kvm_host.h |  2 ++ >>   2 files changed, 14 insertions(+) >> >> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c >> index 305a0e054f81..124655da02ca 100644 >> --- a/arch/arm64/kvm/mmu.c >> +++ b/arch/arm64/kvm/mmu.c >> @@ -1287,6 +1287,18 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm, >>       kvm_nested_s2_wp(kvm); >>   } >> +/** >> + * kvm_arch_supports_cacheable_pfnmap() - Determine whether hardware >> + *      supports cache management. >> + * >> + * Return: True if FWB and DIC is supported. >> + */ >> +bool kvm_arch_supports_cacheable_pfnmap(void) >> +{ >> +    return cpus_have_final_cap(ARM64_HAS_STAGE2_FWB) && >> +           cpus_have_final_cap(ARM64_HAS_CACHE_DIC); >> +} >> + >>   static void kvm_send_hwpoison_signal(unsigned long address, short lsb) >>   { >>       send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, current); >> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h >> index 291d49b9bf05..3750d216d456 100644 >> --- a/include/linux/kvm_host.h >> +++ b/include/linux/kvm_host.h >> @@ -1231,6 +1231,8 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm); >>   /* flush memory translations pointing to 'slot' */ >>   void kvm_arch_flush_shadow_memslot(struct kvm *kvm, >>                      struct kvm_memory_slot *slot); >> +/* hardware support cache management */ >> +bool kvm_arch_supports_cacheable_pfnmap(void); > Won't this cause a build warning on non-ARM builds, b/c there is no > resolution of this function for the other arch's? > Need #ifdef or default-rtn-0 function for arch's that don't have this function? > ah, I see you have the weak function in patch 5/5. But I think you have to move that hunk to this patch, so a bisect won't cause a build warning (or failure, depending on how a distro sets -W in its builds). - Don >>   int kvm_prefetch_pages(struct kvm_memory_slot *slot, gfn_t gfn, >>                  struct page **pages, int nr_pages);